Messages in this thread | | | Date | Thu, 11 Sep 2003 18:08:02 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] schedstat-2.6.0-test5-A1 measuring process scheduling latency |
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On Thu, 11 Sep 2003, Rick Lindsley wrote:
> All the tweaking of the scheduler for interactive processes is still > rather reliant on "when I run X, Y, and Z, and wiggle the mouse, it feels > slower." At best, we might get a more concrete "the music skips every > now and then." It's very hard to develop changes for an environment I > don't have in front of me and can't ever seem to precisely duplicate. > > It's my contention that what we're seeing is scheduler latency: processes > want to run but end up waiting for some period of time. There's currently > no way to capture that short of the descriptions above. This patch adds > counters at various places to measure, among other things, the scheduler > latency. That is, we can now measure the time processes spend waiting > to run after being made runnable. We can also see on average how long > a process runs before giving up (or being kicked off) the cpu.
When I was working on it, I wrote a patch that at every context switch used to register cycle counter timestamp, pid and other things (this per CPU), with the number of samples configurable. This helped me a lot not only to understand latencies, but also process migrations (usefull for balancing thingies). There was a /dev/something where you could collect samples and analyze them. It'd nice to have something like that for 2.6.
- Davide
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