Brendan Gregg

AUGUST 29, 2021

Reads usually have apps waiting on them; writes may not (write-back caching). biolatency From [bcc], this eBPF tool shows a latency histogram of disk I/O. biolatency From [bcc], this eBPF tool shows a latency histogram of disk I/O. Hit Ctrl-C to end. ^C Hit Ctrl-C to end. ^C Counting cache functions.

Cache 105

Cache C++ AWS Latency 105

Brendan Gregg

JULY 2, 2021

biolatency Disk I/O latency histogram heat map. cachestat File system cache statistics line charts. runqlat CPU scheduler latency heat map. Then, having discovered everything is C or Python, some rewrite it all in a different language. execsnoop New processes (via exec(2)) table. opensnoop Files opened table. at the time.

Latency 145

Latency Cache Energy Systems 145

Brendan Gregg

AUGUST 29, 2021

100.00 ^C I'm looking at the r_await column in particular: the average wait time for reads in milliseconds. Reads usually have apps waiting on them; writes may not (write-back caching). biolatency From [bcc], this eBPF tool shows a latency histogram of disk I/O. Hit Ctrl-C to end. ^C Hit Ctrl-C to end. ^C

Cache 40

Cache C++ AWS Systems 40

ACM Sigarch

MARCH 25, 2019

How many buffers are needed to track pending requests as a function of needed bandwidth and expected latency? Can one both minimize latency and maximize throughput for unscheduled work? The M/M/1 queue will show us a required trade-off among (a) allowing unscheduled task arrivals, (b) minimizing latency, and (c) maximizing throughput.

Systems 53

Systems Latency Performance C++ 53

ACM Sigarch

MARCH 18, 2019

How many buffers are needed to track pending requests as a function of needed bandwidth and expected latency? Can one both minimize latency and maximize throughput for unscheduled work? These models are useful for insight regarding the basic computer system performance metrics of latency and throughput (bandwidth). Little’s Law.

Systems 60

Systems Latency Performance Analytics 60

Brendan Gregg

JULY 2, 2021

biolatency Disk I/O latency histogram heat map 5. cachestat File system cache statistics line charts 7. runqlat CPU scheduler latency heat map 10. As an extreme example, I wrote cachestat(8) while on vacation in 2014 for use on the Netflix cloud, which was a mix of Linux 3.2 execsnoop New processes (via exec(2)) table 2.

Open Source 40

Open Source Latency Cache Energy 40