News for hackers. Stuff that matters.

A comment on Linux Performance Analysis. Parent comment

Re:Linux Performance Analysis by caf on Tuesday December 01, 2015 @07:47PM (#10660069)
It will show up like CPU usage - the hyperthread that is waiting for memory will appear busy executing.

perf can record hardware counter events - use "perf list" to see the list - including those that count frontend and backend stalls (stalls in the instruction decoding and execution stages respectively). A high stall ratio / low instructions per cycle throughput is an indicator that you're running into memory bandwidth limitations.

[ Parent | on HN ]
Re:Linux Performance Analysis by odaymansour on Tuesday December 01, 2015 @07:52PM (#10660094)
You've also reminded me that while they do show up as CPU time, they wouldn't be 'user' time (for example in the output of the command 'time')
[ Parent | on HN ]
Re:Linux Performance Analysis by brendangregg on Wednesday December 02, 2015 @04:41AM (#10661928)
If it's user-mode loads and stores, which for applications is pretty common, it is user time. Easy to test.
[ Parent | on HN ]
Re:Linux Performance Analysis by odaymansour on Thursday December 03, 2015 @06:23PM (#10673493)
Thanks for that, I'll take another look at it and see what I've been missing then.
[ Parent | on HN ]