Full Width 
Shortcuts 
Sign Up 
Log In 
Articles 
Reading List More from Evan Jones - Software Engineer | Computer Scientist
This is a reminder that random load balancing is unevenly distributed. If we distribute a set of items randomly across a set of servers (e.g. by hashing, or by randomly selecting a server), the average number of items on each server is num_items / num_servers. It is easy to assume this means each server has close to the same number of items. However, since we are selecting servers at random, they will have different numbers of items, and the imbalance can be important. For load balancing, a reasonable model is that each server has fixed capacity (e.g. it can serve 3000 requests/second, or store 100 items, etc.). We need to divide the total workload over the servers, so that each server stays below its capacity. This means the number of servers is determined by the most loaded server, not the average. This is a classic balls in bins problem that has been well studied, and there are some interesting theoretical results. However, I wanted some specific numbers, so I wrote a small simulation. The summary is that the imbalance depends on the expected number of items per server (that is, num_items / num_servers). This means workload is more balanced with fewer servers, or with more items. This means that dividing a set of items over more servers makes the distribution more unfair, which is a reason we can get worse than linear scaling of a distributed system. Let's make this more concrete with an example. Let's assume we have a workload of 1000 items, and each server can hold a maximum of 100 items. If we place the exact same number of items on each server, we only need 10 servers, and each of them is completely busy. However, if we place the items randomly, then the median (p50) number of items is 100 items. This means half the servers will have more than 100 items, and will be overloaded. If we want less than a 1% chance of an overloaded server, we need to look at the 99th percentile (p99) server load. We need to use at least 13 servers, which has a p99 load of 97 items. For 14 servers, the average is 77 items, so our servers are on average 23% idle. This shows how the imbalance leads to wasted capacity. This is a bit of an extreme example, because the number of items is small. Let's assume we can make the items 10× smaller, say by dividing them into pieces. Our workload now consists of 10k items, and each server has the capacity to hold 1000 (1k) items. Our perfectly balanced workload still needs 10 servers. With random load balancing, to have a less than 1 in 1000 chance of exceeding our capacity, we only need 11 servers, which has a p99 load of 98 items and a p999 of 100 items. With 11 servers, the average number of items is 910 or 91%, so our servers are only 9% idle. This shows how splitting work into smaller pieces improves load balancing. Another way to look at this is to think about a scaling scenario. Let's go back to our workload of 1000 items, where each server can handle 100 items, and we have 13 servers to ensure we have less than a 1% chance of an overloaded server. Now let's assume the amount of work per item doubles, for example because the service has become more popular, so each item has become larger. Now, each server can hold a maximum of 50 items. If we have perfectly linear scaling, we can double the number of servers from 13 to 26 to handle this workload. However, 26 servers has a p99 of 53 items, so we again have a more than 1% chance of overload. We need to use 28 servers which has a p99 of 50 items. This means we doubled the workload, but had to increase the number of servers from 13 to 28, which is 2.15×. This is sub-linear scaling. As a way to visualize the imbalance, the chart below shows the p99 to average ratio, which is a measure of how imbalanced the system is. If everything is perfectly balanced, the value is 1.0. A value of 2.0 means 1% of servers will have double the number of items of the average server. This shows that the imbalance increases with the number of servers, and increases with fewer items. Power of Two Random Choices Another way to improve load balancing is to have smarter placement. Perfect placement can be hard, but it is often possible to use the "power of two random choices" technique: select two servers at random, and place the item on the least loaded of the two. This makes the distribution much more balanced. For 1000 items and 100 items/server, 11 servers has a p999 of 93 items, so much less than 0.1% chance of overload, compared to needing 14 servers with random load balancing. For the scaling scenario where each server can only handle 50 items, we only need 21 servers to have a p999 of 50 items, compared to 28 servers with random load balancing. The downside of the two choices technique is that each request is now more expensive, since it must query two servers instead of one. However, in many cases where the "item not found" requests are much less expensive than the "item found" requests, this can still be a substantial improvement. For another look at how this improves load balancing, with a nice simulation that includes information delays, see Marc Brooker's blog post. Raw simulation output I will share the code for this simulation later. simulating placing items on servers with random selection iterations=10000 (number of times num_items are placed on num_servers) measures the fraction of items on each server (server_items/num_items) and reports the percentile of all servers in the run P99_AVG_RATIO = p99 / average; approximately the worst server compared to average num_items=1000: num_servers=3 p50=0.33300 p95=0.35800 p99=0.36800 p999=0.37900 AVG=0.33333; P99_AVG_RATIO=1.10400; ITEMS_PER_NODE=333.3 num_servers=5 p50=0.20000 p95=0.22100 p99=0.23000 p999=0.24000 AVG=0.20000; P99_AVG_RATIO=1.15000; ITEMS_PER_NODE=200.0 num_servers=10 p50=0.10000 p95=0.11600 p99=0.12300 p999=0.13100 AVG=0.10000; P99_AVG_RATIO=1.23000; ITEMS_PER_NODE=100.0 num_servers=11 p50=0.09100 p95=0.10600 p99=0.11300 p999=0.12000 AVG=0.09091; P99_AVG_RATIO=1.24300; ITEMS_PER_NODE=90.9 num_servers=12 p50=0.08300 p95=0.09800 p99=0.10400 p999=0.11200 AVG=0.08333; P99_AVG_RATIO=1.24800; ITEMS_PER_NODE=83.3 num_servers=13 p50=0.07700 p95=0.09100 p99=0.09700 p999=0.10400 AVG=0.07692; P99_AVG_RATIO=1.26100; ITEMS_PER_NODE=76.9 num_servers=14 p50=0.07100 p95=0.08500 p99=0.09100 p999=0.09800 AVG=0.07143; P99_AVG_RATIO=1.27400; ITEMS_PER_NODE=71.4 num_servers=25 p50=0.04000 p95=0.05000 p99=0.05500 p999=0.06000 AVG=0.04000; P99_AVG_RATIO=1.37500; ITEMS_PER_NODE=40.0 num_servers=50 p50=0.02000 p95=0.02800 p99=0.03100 p999=0.03500 AVG=0.02000; P99_AVG_RATIO=1.55000; ITEMS_PER_NODE=20.0 num_servers=100 p50=0.01000 p95=0.01500 p99=0.01800 p999=0.02100 AVG=0.01000; P99_AVG_RATIO=1.80000; ITEMS_PER_NODE=10.0 num_servers=1000 p50=0.00100 p95=0.00300 p99=0.00400 p999=0.00500 AVG=0.00100; P99_AVG_RATIO=4.00000; ITEMS_PER_NODE=1.0 num_items=2000: num_servers=3 p50=0.33350 p95=0.35050 p99=0.35850 p999=0.36550 AVG=0.33333; P99_AVG_RATIO=1.07550; ITEMS_PER_NODE=666.7 num_servers=5 p50=0.20000 p95=0.21500 p99=0.22150 p999=0.22850 AVG=0.20000; P99_AVG_RATIO=1.10750; ITEMS_PER_NODE=400.0 num_servers=10 p50=0.10000 p95=0.11100 p99=0.11600 p999=0.12150 AVG=0.10000; P99_AVG_RATIO=1.16000; ITEMS_PER_NODE=200.0 num_servers=11 p50=0.09100 p95=0.10150 p99=0.10650 p999=0.11150 AVG=0.09091; P99_AVG_RATIO=1.17150; ITEMS_PER_NODE=181.8 num_servers=12 p50=0.08350 p95=0.09350 p99=0.09800 p999=0.10300 AVG=0.08333; P99_AVG_RATIO=1.17600; ITEMS_PER_NODE=166.7 num_servers=13 p50=0.07700 p95=0.08700 p99=0.09100 p999=0.09600 AVG=0.07692; P99_AVG_RATIO=1.18300; ITEMS_PER_NODE=153.8 num_servers=14 p50=0.07150 p95=0.08100 p99=0.08500 p999=0.09000 AVG=0.07143; P99_AVG_RATIO=1.19000; ITEMS_PER_NODE=142.9 num_servers=25 p50=0.04000 p95=0.04750 p99=0.05050 p999=0.05450 AVG=0.04000; P99_AVG_RATIO=1.26250; ITEMS_PER_NODE=80.0 num_servers=50 p50=0.02000 p95=0.02550 p99=0.02750 p999=0.03050 AVG=0.02000; P99_AVG_RATIO=1.37500; ITEMS_PER_NODE=40.0 num_servers=100 p50=0.01000 p95=0.01400 p99=0.01550 p999=0.01750 AVG=0.01000; P99_AVG_RATIO=1.55000; ITEMS_PER_NODE=20.0 num_servers=1000 p50=0.00100 p95=0.00250 p99=0.00300 p999=0.00400 AVG=0.00100; P99_AVG_RATIO=3.00000; ITEMS_PER_NODE=2.0 num_items=5000: num_servers=3 p50=0.33340 p95=0.34440 p99=0.34920 p999=0.35400 AVG=0.33333; P99_AVG_RATIO=1.04760; ITEMS_PER_NODE=1666.7 num_servers=5 p50=0.20000 p95=0.20920 p99=0.21320 p999=0.21740 AVG=0.20000; P99_AVG_RATIO=1.06600; ITEMS_PER_NODE=1000.0 num_servers=10 p50=0.10000 p95=0.10700 p99=0.11000 p999=0.11320 AVG=0.10000; P99_AVG_RATIO=1.10000; ITEMS_PER_NODE=500.0 num_servers=11 p50=0.09080 p95=0.09760 p99=0.10040 p999=0.10380 AVG=0.09091; P99_AVG_RATIO=1.10440; ITEMS_PER_NODE=454.5 num_servers=12 p50=0.08340 p95=0.08980 p99=0.09260 p999=0.09580 AVG=0.08333; P99_AVG_RATIO=1.11120; ITEMS_PER_NODE=416.7 num_servers=13 p50=0.07680 p95=0.08320 p99=0.08580 p999=0.08900 AVG=0.07692; P99_AVG_RATIO=1.11540; ITEMS_PER_NODE=384.6 num_servers=14 p50=0.07140 p95=0.07740 p99=0.08000 p999=0.08300 AVG=0.07143; P99_AVG_RATIO=1.12000; ITEMS_PER_NODE=357.1 num_servers=25 p50=0.04000 p95=0.04460 p99=0.04660 p999=0.04880 AVG=0.04000; P99_AVG_RATIO=1.16500; ITEMS_PER_NODE=200.0 num_servers=50 p50=0.02000 p95=0.02340 p99=0.02480 p999=0.02640 AVG=0.02000; P99_AVG_RATIO=1.24000; ITEMS_PER_NODE=100.0 num_servers=100 p50=0.01000 p95=0.01240 p99=0.01340 p999=0.01460 AVG=0.01000; P99_AVG_RATIO=1.34000; ITEMS_PER_NODE=50.0 num_servers=1000 p50=0.00100 p95=0.00180 p99=0.00220 p999=0.00260 AVG=0.00100; P99_AVG_RATIO=2.20000; ITEMS_PER_NODE=5.0 num_items=10000: num_servers=3 p50=0.33330 p95=0.34110 p99=0.34430 p999=0.34820 AVG=0.33333; P99_AVG_RATIO=1.03290; ITEMS_PER_NODE=3333.3 num_servers=5 p50=0.20000 p95=0.20670 p99=0.20950 p999=0.21260 AVG=0.20000; P99_AVG_RATIO=1.04750; ITEMS_PER_NODE=2000.0 num_servers=10 p50=0.10000 p95=0.10500 p99=0.10700 p999=0.10940 AVG=0.10000; P99_AVG_RATIO=1.07000; ITEMS_PER_NODE=1000.0 num_servers=11 p50=0.09090 p95=0.09570 p99=0.09770 p999=0.09990 AVG=0.09091; P99_AVG_RATIO=1.07470; ITEMS_PER_NODE=909.1 num_servers=12 p50=0.08330 p95=0.08790 p99=0.08980 p999=0.09210 AVG=0.08333; P99_AVG_RATIO=1.07760; ITEMS_PER_NODE=833.3 num_servers=13 p50=0.07690 p95=0.08130 p99=0.08320 p999=0.08530 AVG=0.07692; P99_AVG_RATIO=1.08160; ITEMS_PER_NODE=769.2 num_servers=14 p50=0.07140 p95=0.07570 p99=0.07740 p999=0.07950 AVG=0.07143; P99_AVG_RATIO=1.08360; ITEMS_PER_NODE=714.3 num_servers=25 p50=0.04000 p95=0.04330 p99=0.04460 p999=0.04620 AVG=0.04000; P99_AVG_RATIO=1.11500; ITEMS_PER_NODE=400.0 num_servers=50 p50=0.02000 p95=0.02230 p99=0.02330 p999=0.02440 AVG=0.02000; P99_AVG_RATIO=1.16500; ITEMS_PER_NODE=200.0 num_servers=100 p50=0.01000 p95=0.01170 p99=0.01240 p999=0.01320 AVG=0.01000; P99_AVG_RATIO=1.24000; ITEMS_PER_NODE=100.0 num_servers=1000 p50=0.00100 p95=0.00150 p99=0.00180 p999=0.00210 AVG=0.00100; P99_AVG_RATIO=1.80000; ITEMS_PER_NODE=10.0 num_items=100000: num_servers=3 p50=0.33333 p95=0.33579 p99=0.33681 p999=0.33797 AVG=0.33333; P99_AVG_RATIO=1.01043; ITEMS_PER_NODE=33333.3 num_servers=5 p50=0.20000 p95=0.20207 p99=0.20294 p999=0.20393 AVG=0.20000; P99_AVG_RATIO=1.01470; ITEMS_PER_NODE=20000.0 num_servers=10 p50=0.10000 p95=0.10157 p99=0.10222 p999=0.10298 AVG=0.10000; P99_AVG_RATIO=1.02220; ITEMS_PER_NODE=10000.0 num_servers=11 p50=0.09091 p95=0.09241 p99=0.09304 p999=0.09379 AVG=0.09091; P99_AVG_RATIO=1.02344; ITEMS_PER_NODE=9090.9 num_servers=12 p50=0.08334 p95=0.08477 p99=0.08537 p999=0.08602 AVG=0.08333; P99_AVG_RATIO=1.02444; ITEMS_PER_NODE=8333.3 num_servers=13 p50=0.07692 p95=0.07831 p99=0.07888 p999=0.07954 AVG=0.07692; P99_AVG_RATIO=1.02544; ITEMS_PER_NODE=7692.3 num_servers=14 p50=0.07143 p95=0.07277 p99=0.07332 p999=0.07396 AVG=0.07143; P99_AVG_RATIO=1.02648; ITEMS_PER_NODE=7142.9 num_servers=25 p50=0.04000 p95=0.04102 p99=0.04145 p999=0.04193 AVG=0.04000; P99_AVG_RATIO=1.03625; ITEMS_PER_NODE=4000.0 num_servers=50 p50=0.02000 p95=0.02073 p99=0.02103 p999=0.02138 AVG=0.02000; P99_AVG_RATIO=1.05150; ITEMS_PER_NODE=2000.0 num_servers=100 p50=0.01000 p95=0.01052 p99=0.01074 p999=0.01099 AVG=0.01000; P99_AVG_RATIO=1.07400; ITEMS_PER_NODE=1000.0 num_servers=1000 p50=0.00100 p95=0.00117 p99=0.00124 p999=0.00132 AVG=0.00100; P99_AVG_RATIO=1.24000; ITEMS_PER_NODE=100.0 power of two choices num_items=1000: num_servers=3 p50=0.33300 p95=0.33400 p99=0.33500 p999=0.33600 AVG=0.33333; P99_AVG_RATIO=1.00500; ITEMS_PER_NODE=333.3 num_servers=5 p50=0.20000 p95=0.20100 p99=0.20200 p999=0.20300 AVG=0.20000; P99_AVG_RATIO=1.01000; ITEMS_PER_NODE=200.0 num_servers=10 p50=0.10000 p95=0.10100 p99=0.10200 p999=0.10200 AVG=0.10000; P99_AVG_RATIO=1.02000; ITEMS_PER_NODE=100.0 num_servers=11 p50=0.09100 p95=0.09200 p99=0.09300 p999=0.09300 AVG=0.09091; P99_AVG_RATIO=1.02300; ITEMS_PER_NODE=90.9 num_servers=12 p50=0.08300 p95=0.08500 p99=0.08500 p999=0.08600 AVG=0.08333; P99_AVG_RATIO=1.02000; ITEMS_PER_NODE=83.3 num_servers=13 p50=0.07700 p95=0.07800 p99=0.07900 p999=0.07900 AVG=0.07692; P99_AVG_RATIO=1.02700; ITEMS_PER_NODE=76.9 num_servers=14 p50=0.07200 p95=0.07300 p99=0.07300 p999=0.07400 AVG=0.07143; P99_AVG_RATIO=1.02200; ITEMS_PER_NODE=71.4 num_servers=25 p50=0.04000 p95=0.04100 p99=0.04200 p999=0.04200 AVG=0.04000; P99_AVG_RATIO=1.05000; ITEMS_PER_NODE=40.0 num_servers=50 p50=0.02000 p95=0.02100 p99=0.02200 p999=0.02200 AVG=0.02000; P99_AVG_RATIO=1.10000; ITEMS_PER_NODE=20.0 num_servers=100 p50=0.01000 p95=0.01100 p99=0.01200 p999=0.01200 AVG=0.01000; P99_AVG_RATIO=1.20000; ITEMS_PER_NODE=10.0 num_servers=1000 p50=0.00100 p95=0.00200 p99=0.00200 p999=0.00300 AVG=0.00100; P99_AVG_RATIO=2.00000; ITEMS_PER_NODE=1.0 power of two choices num_items=2000: num_servers=3 p50=0.33350 p95=0.33400 p99=0.33400 p999=0.33450 AVG=0.33333; P99_AVG_RATIO=1.00200; ITEMS_PER_NODE=666.7 num_servers=5 p50=0.20000 p95=0.20050 p99=0.20100 p999=0.20150 AVG=0.20000; P99_AVG_RATIO=1.00500; ITEMS_PER_NODE=400.0 num_servers=10 p50=0.10000 p95=0.10050 p99=0.10100 p999=0.10100 AVG=0.10000; P99_AVG_RATIO=1.01000; ITEMS_PER_NODE=200.0 num_servers=11 p50=0.09100 p95=0.09150 p99=0.09200 p999=0.09200 AVG=0.09091; P99_AVG_RATIO=1.01200; ITEMS_PER_NODE=181.8 num_servers=12 p50=0.08350 p95=0.08400 p99=0.08400 p999=0.08450 AVG=0.08333; P99_AVG_RATIO=1.00800; ITEMS_PER_NODE=166.7 num_servers=13 p50=0.07700 p95=0.07750 p99=0.07800 p999=0.07800 AVG=0.07692; P99_AVG_RATIO=1.01400; ITEMS_PER_NODE=153.8 num_servers=14 p50=0.07150 p95=0.07200 p99=0.07250 p999=0.07250 AVG=0.07143; P99_AVG_RATIO=1.01500; ITEMS_PER_NODE=142.9 num_servers=25 p50=0.04000 p95=0.04050 p99=0.04100 p999=0.04100 AVG=0.04000; P99_AVG_RATIO=1.02500; ITEMS_PER_NODE=80.0 num_servers=50 p50=0.02000 p95=0.02050 p99=0.02100 p999=0.02100 AVG=0.02000; P99_AVG_RATIO=1.05000; ITEMS_PER_NODE=40.0 num_servers=100 p50=0.01000 p95=0.01050 p99=0.01100 p999=0.01100 AVG=0.01000; P99_AVG_RATIO=1.10000; ITEMS_PER_NODE=20.0 num_servers=1000 p50=0.00100 p95=0.00150 p99=0.00200 p999=0.00200 AVG=0.00100; P99_AVG_RATIO=2.00000; ITEMS_PER_NODE=2.0 power of two choices num_items=5000: num_servers=3 p50=0.33340 p95=0.33360 p99=0.33360 p999=0.33380 AVG=0.33333; P99_AVG_RATIO=1.00080; ITEMS_PER_NODE=1666.7 num_servers=5 p50=0.20000 p95=0.20020 p99=0.20040 p999=0.20060 AVG=0.20000; P99_AVG_RATIO=1.00200; ITEMS_PER_NODE=1000.0 num_servers=10 p50=0.10000 p95=0.10020 p99=0.10040 p999=0.10040 AVG=0.10000; P99_AVG_RATIO=1.00400; ITEMS_PER_NODE=500.0 num_servers=11 p50=0.09100 p95=0.09120 p99=0.09120 p999=0.09140 AVG=0.09091; P99_AVG_RATIO=1.00320; ITEMS_PER_NODE=454.5 num_servers=12 p50=0.08340 p95=0.08360 p99=0.08360 p999=0.08380 AVG=0.08333; P99_AVG_RATIO=1.00320; ITEMS_PER_NODE=416.7 num_servers=13 p50=0.07700 p95=0.07720 p99=0.07720 p999=0.07740 AVG=0.07692; P99_AVG_RATIO=1.00360; ITEMS_PER_NODE=384.6 num_servers=14 p50=0.07140 p95=0.07160 p99=0.07180 p999=0.07180 AVG=0.07143; P99_AVG_RATIO=1.00520; ITEMS_PER_NODE=357.1 num_servers=25 p50=0.04000 p95=0.04020 p99=0.04040 p999=0.04040 AVG=0.04000; P99_AVG_RATIO=1.01000; ITEMS_PER_NODE=200.0 num_servers=50 p50=0.02000 p95=0.02020 p99=0.02040 p999=0.02040 AVG=0.02000; P99_AVG_RATIO=1.02000; ITEMS_PER_NODE=100.0 num_servers=100 p50=0.01000 p95=0.01020 p99=0.01040 p999=0.01040 AVG=0.01000; P99_AVG_RATIO=1.04000; ITEMS_PER_NODE=50.0 num_servers=1000 p50=0.00100 p95=0.00120 p99=0.00140 p999=0.00140 AVG=0.00100; P99_AVG_RATIO=1.40000; ITEMS_PER_NODE=5.0 power of two choices num_items=10000: num_servers=3 p50=0.33330 p95=0.33340 p99=0.33350 p999=0.33360 AVG=0.33333; P99_AVG_RATIO=1.00050; ITEMS_PER_NODE=3333.3 num_servers=5 p50=0.20000 p95=0.20010 p99=0.20020 p999=0.20030 AVG=0.20000; P99_AVG_RATIO=1.00100; ITEMS_PER_NODE=2000.0 num_servers=10 p50=0.10000 p95=0.10010 p99=0.10020 p999=0.10020 AVG=0.10000; P99_AVG_RATIO=1.00200; ITEMS_PER_NODE=1000.0 num_servers=11 p50=0.09090 p95=0.09100 p99=0.09110 p999=0.09110 AVG=0.09091; P99_AVG_RATIO=1.00210; ITEMS_PER_NODE=909.1 num_servers=12 p50=0.08330 p95=0.08350 p99=0.08350 p999=0.08360 AVG=0.08333; P99_AVG_RATIO=1.00200; ITEMS_PER_NODE=833.3 num_servers=13 p50=0.07690 p95=0.07700 p99=0.07710 p999=0.07720 AVG=0.07692; P99_AVG_RATIO=1.00230; ITEMS_PER_NODE=769.2 num_servers=14 p50=0.07140 p95=0.07160 p99=0.07160 p999=0.07170 AVG=0.07143; P99_AVG_RATIO=1.00240; ITEMS_PER_NODE=714.3 num_servers=25 p50=0.04000 p95=0.04010 p99=0.04020 p999=0.04020 AVG=0.04000; P99_AVG_RATIO=1.00500; ITEMS_PER_NODE=400.0 num_servers=50 p50=0.02000 p95=0.02010 p99=0.02020 p999=0.02020 AVG=0.02000; P99_AVG_RATIO=1.01000; ITEMS_PER_NODE=200.0 num_servers=100 p50=0.01000 p95=0.01010 p99=0.01020 p999=0.01020 AVG=0.01000; P99_AVG_RATIO=1.02000; ITEMS_PER_NODE=100.0 num_servers=1000 p50=0.00100 p95=0.00110 p99=0.00120 p999=0.00120 AVG=0.00100; P99_AVG_RATIO=1.20000; ITEMS_PER_NODE=10.0 power of two choices num_items=100000: num_servers=3 p50=0.33333 p95=0.33334 p99=0.33335 p999=0.33336 AVG=0.33333; P99_AVG_RATIO=1.00005; ITEMS_PER_NODE=33333.3 num_servers=5 p50=0.20000 p95=0.20001 p99=0.20002 p999=0.20003 AVG=0.20000; P99_AVG_RATIO=1.00010; ITEMS_PER_NODE=20000.0 num_servers=10 p50=0.10000 p95=0.10001 p99=0.10002 p999=0.10002 AVG=0.10000; P99_AVG_RATIO=1.00020; ITEMS_PER_NODE=10000.0 num_servers=11 p50=0.09091 p95=0.09092 p99=0.09093 p999=0.09093 AVG=0.09091; P99_AVG_RATIO=1.00023; ITEMS_PER_NODE=9090.9 num_servers=12 p50=0.08333 p95=0.08335 p99=0.08335 p999=0.08336 AVG=0.08333; P99_AVG_RATIO=1.00020; ITEMS_PER_NODE=8333.3 num_servers=13 p50=0.07692 p95=0.07694 p99=0.07694 p999=0.07695 AVG=0.07692; P99_AVG_RATIO=1.00022; ITEMS_PER_NODE=7692.3 num_servers=14 p50=0.07143 p95=0.07144 p99=0.07145 p999=0.07145 AVG=0.07143; P99_AVG_RATIO=1.00030; ITEMS_PER_NODE=7142.9 num_servers=25 p50=0.04000 p95=0.04001 p99=0.04002 p999=0.04002 AVG=0.04000; P99_AVG_RATIO=1.00050; ITEMS_PER_NODE=4000.0 num_servers=50 p50=0.02000 p95=0.02001 p99=0.02002 p999=0.02002 AVG=0.02000; P99_AVG_RATIO=1.00100; ITEMS_PER_NODE=2000.0 num_servers=100 p50=0.01000 p95=0.01001 p99=0.01002 p999=0.01002 AVG=0.01000; P99_AVG_RATIO=1.00200; ITEMS_PER_NODE=1000.0 num_servers=1000 p50=0.00100 p95=0.00101 p99=0.00102 p999=0.00102 AVG=0.00100; P99_AVG_RATIO=1.02000; ITEMS_PER_NODE=100.0
I was wondering: how often do nanosecond timestamps collide on modern systems? The answer is: very often, like 5% of all samples, when reading the clock on all 4 physical cores at the same time. As a result, I think it is unsafe to assume that a raw nanosecond timestamp is a unique identifier. I wrote a small test program to test this. I used Go, which records both the "absolute" time and the "monotonic clock" relative time on each call to time.Now(), so I compared both the relative difference between consecutive timestamps, as well as just the absolute timestamps. As expected, the behavior depends on the system, so I observe very different results on Mac OS X and Linux. On Linux, within a single thread, both the absolute and monotonic times always increase. On my system, the minimum increment was 32 ns. Between threads, approximately 5% of the absolute times were exactly the same as other threads. Even with 2 threads on a 4 core system, approximately 2% of timestamps collided. On Mac OS X: the absolute time has microsecond resolution, so there are an astronomical number of collisions when I repeat this same test. Even within a thread I often observe the monotonic clock not increment. See the test program on Github if you are curious.
The read() and write() system calls take a variable-length byte array as an argument. As a simplified model, the time for the system call should be some constant "per-call" time, plus time directly proportional to the number of bytes in the array. That is, the time for each call should be time = (per_call_minimum_time) + (array_len) × (per_byte_time). With this model, using a larger buffer should increase throughput, asymptotically approaching 1/per_byte_time. I was curious: do real system calls behave this way? What are the ideal buffer sizes for read() and write() if we want to maximize throughput? I decided to do some experiments with blocking I/O. These are not rigorous, and I suspect the results will vary significantly if the hardware and software are different than one the system I tested. The really short answer is that a buffer of 32 KiB is a good starting point on today's systems, and I would want to measure the performance to go beyond that. However, for large writes, performance can increase. On Linux, the simple model holds for small buffers (≤ 4 KiB), but once the program approaches the maximum throughput, the throughput becomes highly variable and in many cases decreases as the buffers get larger. For blocking I/O, approximately 32 KiB is large enough to hit the maximum throughput for read(), but write() throughput improves with buffers up to around 256 KiB - 1 MiB. The reason for the asymmetry is that the Linux kernel will only write less than the entire buffer (a "short write") if there is an error (e.g. a signal causing EINTR). Thus, larger write buffers means the operating system needs to switch to the process less often. On the other head, "short reads", where a read() returns less than the maximum length, become increasingly common as the buffer size increases, which diminishes the benefit. There is a SO_RCVLOWAT socket option to change this that I did not test. The experiments were run on two 16 CPU Google Cloud T2D instances, which use AMD EPYC Milan processors (3rd generation, released in 2021). Each core is a real physical core. I used Ubuntu 23.04 running kernel 6.2.0-1005-gcp. My benchmark program is written in Rust and is available on Github. On localhost, Unix sockets were able to transfer data at approximately 9000 MiB/s. Localhost TCP sockets were a bit slower, around 7000 MiB/s. When using two separate cloud VMs with a networking throughput limit of 32 Gbps = 3800 MiB/s, I needed to use 6 TCP sockets to reliably reach that maximum throughput. A single TCP socket gets around 1400 MiB/s with 256 KiB buffers, with peaks as high as 2200 MiB/s. Experiment 1: /dev/zero and /dev/urandom My first experiment is reading from the /dev/zero and /dev/urandom devices. These are software devices implemented by the kernel, so they should have low overhead and low variability, since other tasks are not involved. Reading from /dev/urandom should be much slower than /dev/zero since the kernel must generate random bytes, rather than just zeros. The chart below shows the throughput for reading from /dev/zero as the buffer size is increased. The results show that the basic linear time per system call model holds until the system reaches maximum throughput (256 kiB buffer = 39000 MiB/s for /dev/zero, or 16 kiB = 410 MiB/s for /dev/urandom). As the buffer size increases further, the throughput decreases as the buffers get too big. This suggests that some other cost for larger buffers starts to outweigh the reduction in number of system calls. Perhaps CPU caches become less effective? The AMD EPYC Milan (3rd gen) CPU I tested on has 32 KiB of L1 data cache and 512 KiB of L2 data cache per core. The performance decreases don't exactly line up with these numbers, but it still seems plausible. The numbers for /dev/urandom are substantially lower, but otherwise similar. I did a linear least-squares fit on the average time per system call, shown in the following chart. If I use all the data, the fit is not good, because the trend changes for larger buffers. However, if I use the data up to the maximum throughput at 256 KiB, the fit is very good, as shown on the chart below. The linear fit models the minimum time per system call as 167 ns, with 0.0235 ns/byte additional time. If we want to use smaller buffers, using a 64 KiB buffer for reading from /dev/zero gets within 95% of the maximum throughput. Experiment 2: Unix and localhost TCP sockets Exchanging data with other processes is the thing I am actually interested in, so I tested Unix and TCP sockets on a single machine. In this case, I varied both the write buffer size and the read buffer size. Unfortunately, these results vary a lot. A more robust comparison would require running each experiment many times, and using some sort of statistical comparison. However, this "quick and dirty" experiment satisfied my curiousity, so I didn't do that. As a result, my conclusions here are vague. The simple model that increasing buffer size should decrease overhead is true, but only until the buffers are about 4 KiB. Above that point, the results start to be highly variable, and it is much harder to draw general conclusion. However, appears that increasing the write buffer size generally is quite helpful up to at least 256 KiB, and often needed as much as 1 MiB to get the highest localhost throughput. I suspect this is because on Linux with blocking sockets, write() will not return until it has written all the data in the buffer, unless there is an error (e.g. EINTR). As a result, passing a large buffer means the kernel can do a lot of the work without needing to switch back to user space. Unfortunately, the same is not true for read(), which often returns "short reads" with any data that is available in the buffer. This starts with buffer sizes around 2 KiB, with the percentage of short reads increasing as the buffer size gets larger. This means the simple model does not hold, because we aren't actually increasing the bytes per read call. I suspect this is a factor which means this microbenchmark is likely not representative of real programs. A real program will do something with the buffer, which will provide time for more data to be buffered in the kernel, and would probably decrease the number of short reads. This likely means larger buffers are in practice more useful than this microbenchmark suggests. As a result of this, the highest throughput often was achievable with small read buffers. I'm somewhat arbitrarily selecting 16 KiB at the best read buffer, and 256 KiB as the best write buffer, although a 1 MiB write buffer seems to be To give a sense of how variable the results are, the plot below shows the local Unix socket throughput for each read and write buffer throughput size. I apologize for the ugly plot. I did not want to spend the time to make it more beautiful. This plot is interactive so you can slice the data to the area of interest. I recommend zooming in to the left hand size with read buffers up to about 300 KiB. The first thing to note is at least on Linux with blocking sockets, the writer will almost never have a "short write", where the write system call returns before writing all the data in the buffer. Unless there is a signal (EINTR) or some other "error" condition, write() will not return until all the bytes are written. The same is not true for reads. The read() system call will often return a "short" read, starting around buffer sizes of 2 KiB. The percentage of short reads generally increases as buffer sizes get bigger, which is logical. Another note is that sockets have in-kernel send and receive buffers. I did not tune these at all. It is possible that better performance is possible by tuning these settings, but that was not my goal. I wanted to know what happens "out of the box" for general-purpose programs without any special tuning. Experiment 3: TCP between two hosts In this experiment, I used two separate hosts connected with 32 Gbps networking in Google Cloud. I first tested the TCP throughput using iperf, to independently verify the network performance. A single TCP connection with iperf is not enough to fully utilize the network. I tried fiddling with some command line options and with Kernel settings like net.ipv4.tcp_rmem and wasn't able to get much better than about 12 Gb/s = 1400 MiB/s. The throughput is also highly varible. Here is some example output with iperf reporting at 2 second intervals, where you can see the throughput ranging from 10 to 19 Gb/s, with an average over the entire interval of 12 Gb/s. To hit the maximum network throughput, I need to use 6 or more parallel TCP connections (iperf -c IP_ADDRESS --time 60 --interval 2 -l 262144 -P 6). Using 3 connections gets around 26 Gb/s, and using 4 or 5 will occasionally hit the maximum, but will also occasionally drop down. Using at least 6 seems to reliably stay at the maximum. Due to this variability, it is hard to draw any conclusions about buffer size. In particular: a single TCP connection is not limited by CPU. The system uses about 40% of a single CPU core, basically all in the kernel. This is more about how the buffer sizes may impact scheduling choices. That said, it is clear that you cannot hit the maximum throughput with a small write buffer. The experiments with 4 KiB write buffers reached approximately 300 MiB/s, while an 8 KiB write buffer was much faster, around 1400 MiB/s. Larger still generally seems better, up to around 256 KiB, which occasionally reached 2200 MiB/s = 17.6 Gb/s. The plot below shows the TCP socket throughput for each read and write buffer size. Again, I apologize for the ugly plot.
This is a post for myself, because I wasted a lot of time understanding this bug, and I want to be able to remember it in the future. I expect close to zero others to be interested. The C standard library function isspace() returns a non-zero value (true) for the six "standard" ASCII white-space characters ('\t', '\n', '\v', '\f', '\r', ' '), and any locale-specific characters. By default, a program starts in the "C" locale, which will only return true for the six ASCII white-space characters. However, if the program changes locales, it can return true for other values. As a result, unless you really understand locales, you should use your own version of this function, or ICU4C's u_isspace() function. An implementation of isspace() for ASCII is one line: /* Returns true for the 6 ASCII white-space characters: \t \n \v \f \r ' '. */ int isspace_ascii(int c) { return c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r' || c == ' '; } I ran into this because On Mac OS X, Postgres switches to the system's default locale, which is something that uses UTF-8 (e.g. en_US.UTF-8, fr_CA.UTF-8, etc). In this case, isspace() returns true for Unicode white-space values, which includes 0x85 = NEL = Next Line, and 0xA0 = NBSP = No-Break Space. This caused a bug in parsing Postgres Hstore values that use Unicode. I have attempted to submit a patch to fix this (mailing list post, commitfest entry). For a program to demonstrate the behaviour on different systems, see isspace_locale on Github.
More in programming
To be a successful founder, you have to believe that what you're working on is going to work — despite knowing it probably won't! That sounds like an oxymoron, but it's really not. Believing that what you're building is going to work is an essential component of coming to work with the energy, fortitude, and determination it's going to require to even have a shot. Knowing it probably won't is accepting the odds of that shot. It's simply the reality that most things in business don't work out. At least not in the long run. Most businesses fail. If not right away, then eventually. Yet the world economy is full of entrepreneurs who try anyway. Not because they don't know the odds, but because they've chosen to believe they're special. The best way to balance these opposing points — the conviction that you'll make it work, the knowledge that it probably won't — is to do all your work in a manner that'll make you proud either way. If it doesn't work, you still made something you wouldn't be ashamed to put your name on. And if it does work, you'll beam with pride from making it on the basis of something solid. The deep regret from trying and failing only truly hits when you look in the mirror and see Dostoevsky staring back at you with this punch to the gut: "Your worst sin is that you have destroyed and betrayed yourself for nothing." Oof. Believe it's going to work. Build it in a way that makes you proud to sign it. Base your worth on a human on something greater than a business outcome.
I learned a new word: ductile. Do you know it? I’m particularly interested in its usage in a physics/engineering setting when talking about materials. Here’s an answer on Quora to: “What is ductile?” Ductility is the ability of a material to be permanently deformed without cracking. In engineering we talk about elastic deformation as deformation which is reversed once the load is removed for example a spring, conversely plastic deformation isn’t reversed. Ductility is the amount (usually expressed as a ratio) of plastic deformation that a material can undergo before it cracks or tears. I read that and started thinking about the “ductility” of languages like HTML, CSS, and JS. Specifically: how much deformation can they undergo before breaking? HTML, for example, is famously forgiving. It can be stretched, drawn out, or deformed in a variety of ways without breaking. Take this short snippet of HTML: <!doctype html> <title>My site</title> <p>Hello world! <p>Nice to meet you That is valid HTML. But it can also be “drawn out” for readability without losing any of its meaning. It’ll still render the same in the browser: <!doctype html> <html> <head> <title>My site</title> </head> <body> <p>Hello world!</p> <p>Nice to meet you.</p> </body> </html> This capacity for the language to undergo a change in form without breaking is its “ductility”. HTML has some pull before it breaks. JS, on the other hand, doesn’t have the same kind of ductility. Forget a quotation mark and boom! Stretch it a little and it breaks. console.log('works!'); // -> works! console.log('works!); // Uncaught SyntaxError: Invalid or unexpected token I suppose some would say “this isn’t ductility, this is merely forgiving error-parsing”. Ok, sure. Nevertheless, I’m writing here because I learned this new word that has very practical meaning in another discipline to talk about the ability of materials to be stretched and deformed without breaking. I think we need more of that in software. More resiliency. More malleability. More ductility — prioritized in our materials (tools, languages, paradigms) so we can talk more about avoiding sudden failure. Email · Mastodon · Bluesky
I recently went into a deep dive on “UART” and will publish a much longer article on the topic. This is just a recap of the basics to help put things in context. Many tutorials focus on using UART over USB, which adds many layers of abstraction, hiding what it actually is. Here, I deliberately … Continue reading How to use “real” UART → The post How to use “real” UART appeared first on Quentin Santos.
You know about Critical Race Theory, right? It says that if there’s an imbalance in, say, income between races, it must be due to discrimination. This is what wokism seems to be, and it’s moronic and false. The right wing has invented something equally stupid. Introducing Critical Trade Theory, stolen from this tweet. If there’s an imbalance in trade between countries, it must be due to unfair practices. (not due to the obvious, like one country is 10x richer than the other) There’s really only one way the trade deficits will go away, and that’s if trade goes to zero (or maybe if all these countries become richer than America). Same thing with the race deficits, no amount of “leg up” bullshit will change them. Why are all the politicians in America anti-growth anti-reality idiots who want to drive us into the poor house? The way this tariff shit is being done is another stupid form of anti-merit benefits to chosen groups of people, with a whole lot of grift to go along with it. Makes me just not want to play.
One of the most memorable quotes in Arthur Miller’s The Death of a Salesman comes from Uncle Ben, who describes his path to becoming wealthy as, “When I was seventeen, I walked into the jungle, and when I was twenty-one I walked out. And by God I was rich.” I wish I could describe the path to learning engineering strategy in similar terms, but by all accounts it’s a much slower path. Two decades in, I am still learning more from each project I work on. This book has aimed to accelerate your learning path, but my experience is that there’s still a great deal left to learn, despite what this book has hoped to accomplish. This final chapter is focused on the remaining advice I have to give on how you can continue to improve at strategy long after reading this book’s final page. Inescapably, this chapter has become advice on writing your own strategy for improving at strategy. You are already familiar with my general suggestions on creating strategy, so this chapter provides focused advice on creating your own plan to get better at strategy. It covers: Exploring strategy creation to find strategies you can learn from via public and private resources, and through creating learning communities How to diagnose the strategies you’ve found, to ensure you learn the right lessons from each one Policies that will help you find ways to perform and practice strategy within your organization, whether or not you have organizational authority Operational mechanisms to hold yourself accountable to developing a strategy practice My final benediction to you as a strategy practitioner who has finished reading this book With that preamble, let’s write this book’s final strategy: your personal strategy for developing your strategy practice. This is an exploratory, draft chapter for a book on engineering strategy that I’m brainstorming in #eng-strategy-book. As such, some of the links go to other draft chapters, both published drafts and very early, unpublished drafts. Exploring strategy creation Ideally, we’d start our exploration of how to improve at engineering strategy by reading broadly from the many publicly available examples. Unfortunately, there simply aren’t many easily available works to learn from others’ experience. Nonetheless, resources do exist, and we’ll discuss the three categories that I’ve found most useful: Public resources on engineering strategy, such as companies’ engineering blogs Private and undocumented strategies available through your professional network Learning communities that you build together, including ongoing learning circles Each of these is explored in its own section below. Public resources While there aren’t as many public engineering strategy resources as I’d like, I’ve found that there are still a reasonable number available. This book collects a number of such resources in the appendix of engineering strategy resources. That appendix also includes some individuals’ blog posts that are adjacent to this topic. You can go a long way by searching and prompting your way into these resources. As you read them, it’s important to recognize that public strategies are often misleading, as discussed previously in evaluating strategies. Everyone writing in public has an agenda, and that agenda often means that they’ll omit important details to make themselves, or their company, come off well. Make sure you read through the lines rather than taking things too literally. Private resources Ironically, where public resources are hard to find, I’ve found it much easier to find privately held strategy resources. While private recollections are still prone to inaccuracies, the incentives to massage the truth are less pronounced. The most useful sources I’ve found are: peers’ stories – strategies are often oral histories, and they are shared freely among peers within and across companies. As you build out your professional network, you can usually get access to any company’s engineering strategy on any topic by just asking. There are brief exceptions. Even a close peer won’t share a sensitive strategy before its existence becomes obvious externally, but they’ll be glad to after it does. People tend to over-estimate how much information companies can keep private anyway: even reading recent job postings can usually expose a surprising amount about a company. internal strategy archaeologists – while surprisingly few companies formally collect their strategies into a repository, the stories are informally collected by the tenured members of the organization. These folks are the company’s strategy archaeologists, and you can learn a great deal by explicitly consulting them becoming a strategy archaeologist yourself – whether or not you’re a tenured member of your company, you can learn a tremendous amount by starting to build your own strategy repository. As you start collecting them, you’ll interest others in contributing their strategies as well. As discussed in Staff Engineer’s section on the Write five then synthesize approach to strategy, over time you can foster a culture of documentation where one didn’t exist before. Even better, building that culture doesn’t require any explicit authority, just an ongoing show of excitement. There are other sources as well, ranging from attending the hallway track in conferences to organizing dinners where stories are shared with a commitment to privacy. Working in community My final suggestion for seeing how others work on strategy is to form a learning circle. I formed a learning circle when I first moved into an executive role, and at this point have been running it for more than five years. What’s surprised me the most is how much I’ve learned from it. There are a few reasons why ongoing learning circles are exceptional for sharing strategy: Bi-directional discussion allows so much more learning and understanding than mono-directional communication like conference talks or documents. Groups allow you to learn from others’ experiences and others’ questions, rather than having to guide the entire learning yourself. Continuity allows you to see the strategy at inception, during the rollout, and after it’s been in practice for some time. Trust is built slowly, and you only get the full details about a problem when you’ve already successfully held trust about smaller things. An ongoing group makes this sort of sharing feasible where a transient group does not. Although putting one of these communities together requires a commitment, they are the best mechanism I’ve found. As a final secret, many people get stuck on how they can get invited to an existing learning circle, but that’s almost always the wrong question to be asking. If you want to join a learning circle, make one. That’s how I got invited to mine. Diagnosing your prior and current strategy work Collecting strategies to learn from is a valuable part of learning. You also have to determine what lessons to learn from each strategy. For example, you have to determine whether Calm’s approach to resourcing Engineering-driven projects is something to copy or something to avoid. What I’ve found effective is to apply the strategy rubric we developed in the “Is this strategy any good?” chapter to each of the strategies you’ve collected. Even by splitting a strategy into its various phases, you’ll learn a lot. Applying the rubric to each phase will teach you more. Each time you do this to another strategy, you’ll get a bit faster at applying the rubric, and you’ll start to see interesting, recurring patterns. As you dig into a strategy that you’ve split into phases and applied the evaluation rubric to, here are a handful of questions that I’ve found interesting to ask myself: How long did it take to determine a strategy’s initial phase could be improved? How high was the cost to fund that initial phase’s discovery? Why did the strategy reach its final stage and get repealed or replaced? How long did that take to get there? If you had to pick only one, did this strategy fail in its approach to exploration, diagnosis, policy or operations? To what extent did the strategy outlive the tenure of its primary author? Did it get repealed quickly after their departure, did it endure, or was it perhaps replaced during their tenure? Would you generally repeat this strategy, or would you strive to avoid repeating it? If you did repeat it, what conditions seem necessary to make it a success? How might you apply this strategy to your current opportunities and challenges? It’s not necessary to work through all of these questions for every strategy you’re learning from. I often try to pick the two that I think might be most interesting for a given strategy. Policy for improving at strategy At a high level, there are just a few key policies to consider for improving your strategic abilities. The first is implementing strategy, and the second is practicing implementing strategy. While those are indeed the starting points, there are a few more detailed options worth consideration: If your company has existing strategies that are not working, debug one and work to fix it. If you lack the authority to work at the company scope, then decrease altitude until you find an altitude you can work at. Perhaps setting Engineering organizational strategies is beyond your circumstances, but strategy for your team is entirely accessible. If your company has no documented strategies, document one to make it debuggable. Again, if operating at a high altitude isn’t attainable for some reason, operate at a lower altitude that is within reach. If your company’s or team’s strategies are effective but have low adoption, see if you can iterate on operational mechanisms to increase adoption. Many such mechanisms require no authority at all, such as low-noise nudges or the model-document-share approach. If existing strategies are effective and have high adoption, see if you can build excitement for a new strategy. Start by mining for which problems Staff-plus engineers and senior managers believe are important. Once you find one, you have a valuable strategy vein to start mining. If you don’t feel comfortable sharing your work internally, then try writing proposals while only sharing them to a few trusted peers. You can even go further to only share proposals with trusted external peers, perhaps within a learning circle that you create or join. Trying all of these at once would be overwhelming, so I recommend picking one in any given phase. If you aren’t able to make traction, then try another until something works. It’s particularly important to recognize in your diagnosis where things are not working–perhaps you simply don’t have the sponsorship you need to enforce strategy so you need to switch towards suggesting strategies instead–and you’ll find something that works. What if you’re not allowed to do strategy? If you’re looking to find one, you’ll always unearth a reason why it’s not possible to do strategy in your current environment. If you’ve convinced yourself that there’s simply no policy that would allow you to do strategy in your current role, then the two most useful levers I’ve found are: Lower your altitude – there’s always a scale where you can perform strategy, even if it’s just your team or even just yourself. Only you can forbid yourself from developing personal strategies. Practice rather than perform – organizations can only absorb so much strategy development at a given time, so sometimes they won’t be open to you doing more strategy. In that case, you should focus on practicing strategy work rather than directly performing it. Only you can stop yourself from practice. Don’t believe the hype: you can always do strategy work. Operating your strategy improvement policies As the refrain goes, even the best policies don’t accomplish much if they aren’t paired with operational mechanisms to ensure the policies actually happen, and debug why they aren’t happening. Although it’s tempting to ignore operations when it comes to our personal habits, I think that would be a mistake: our personal habits have the most significant long-term impact on ourselves, and are the easiest habits to ignore since others generally won’t ask about them. The mechanisms I’d recommend: Explicitly track the strategies that you’ve implemented, refined, documented, or read. This should be in a document, spreadsheet or folder where you can explicitly see if you have or haven’t done the work. Review your tracked strategies every quarter: are you working on the expected number and in the expected way? If not, why not? Ideally, your review should be done in community with a peer or a learning circle. It’s too easy to deceive yourself, it’s much harder to trick someone else. If your periodic review ever discovers that you’re simply not doing the work you expected, sit down for an hour with someone that you trust–ideally someone equally or more experienced than you–and debug what’s going wrong. Commit to doing this before your next periodic review. Tracking your personal habits can feel a bit odd, but it’s something I highly recommend. I’ve been setting and tracking personal goals for some time now—for example, in my 2024 year in review—and have benefited greatly from it. Too busy for strategy Many companies convince themselves that they’re too much in a rush to make good decisions. I’ve certainly gotten stuck in this view at times myself, although at this point in my career I find it increasingly difficult to not recognize that I have a number of tools to create time for strategy, and an obligation to do strategy rather than inflict poor decisions on the organizations I work in. Here’s my advice for creating time: If you’re not tracking how often you’re creating strategies, then start there. If you’ve not worked on a single strategy in the past six months, then start with one. If implementing a strategy has been prohibitively time consuming, then focus on practicing a strategy instead. If you do try all those things and still aren’t making progress, then accept your reality: you don’t view doing strategy as particularly important. Spend some time thinking about why that is, and if you’re comfortable with your answer, then maybe this is a practice you should come back to later. Final words At this point, you’ve read everything I have to offer on drafting engineering strategy. I hope this has refined your view on what strategy can be in your organization, and has given you the tools to draft a more thoughtful future for your corner of the software engineering industry. What I’d never ask is for you to wholly agree with my ideas here. They are my best thinking on this topic, but strategy is a topic where I’m certain Hegel’s world view is the correct one: even the best ideas here are wrong in interesting ways, and will be surpassed by better ones.
