3 ms·

I loved the latency numbers posted by one stackoverflow engineers Nick Craver: https://nickcraver.com/blog/2019/08/06/stack-overflow-how-we-do-app-caching/ http

by nojvek 6y ago

I loved the latency numbers posted by one stackoverflow engineers Nick Craver: https://nickcraver.com/blog/2019/08/06/stack-overflow-how-we-do-app-caching/ https://nickcraver.com/blog/2019/08/06/stack-overflow-how-we... L1: 1.3ns L2: 3.92ns (3x slower) L3: 11.11ns (8.5x slower) DDR4 RAM: 100ns (77x slower) NVMe SSD: 120,000ns (92,307x slower) SATA/SAS SSD: 400,000ns (307,692x slower) Rotational HDD: 2–6ms (1,538,461x slower) Microsoft Live Login: 12 redirects and 5s (3,846,153,846x slower, approximately) “How many Microsoft Live Logins before this thing loads?”

skytreader 6y ago
Great idea! I think this is the way to make this more relevant and easier to consume. Besides, I think the point of the exercise is not to "know" that reading 1MB sequentially from memory is 250K ns but rather that it is worth 50K branch mispredicts. Knowing these numbers won't make you a better engineer, but being able to compare them (and influence your design decisions with it) will. Though every now and then you get some time-critical tasks in which case the actual numbers might matter. But I imagine at that scale so much more factors will influence your execution that ballpark estimates are nowhere close to tight. Sure 1KB over 1Gbps is 10K ns and you can extrapolate from that how long your 1TB data migration will take. Then it's more worthwhile to check Grafana and reason out from the bandwidth trend.