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SubjectRe: [PATCHv2 00/18] perf tools: Factor ordered samples queue
On 6/18/14, 8:58 AM, Jiri Olsa wrote:
> hi,
> this patchset factors session's ordered samples queue,
> and allows to limit the size of this queue.
>
> v2 changes:
> - several small changes for review comments (Namhyung)
>
>
> The report command queues events till any of following
> conditions is reached:
> - PERF_RECORD_FINISHED_ROUND event is processed
> - end of the file is reached
>
> Any of above conditions will force the queue to flush some
> events while keeping all allocated memory for next events.
>
> If PERF_RECORD_FINISHED_ROUND is missing the queue will
> allocate memory for every single event in the perf.data.
> This could lead to enormous memory consuption and speed
> degradation of report command for huge perf.data files.
>
> With the quue allocation limit of 100 MB, I've got around
> 15% speedup on reporting of ~10GB perf.data file.
>
> current code:
> Performance counter stats for './perf.old report --stdio -i perf-test.data' (3 runs):
>
> 621,685,704,665 cycles ( +- 0.52% )
> 873,397,467,969 instructions ( +- 0.00% )
>
> 286.133268732 seconds time elapsed ( +- 1.13% )
>
> with patches:
> Performance counter stats for './perf report --stdio -i perf-test.data' (3 runs):
>
> 603,933,987,185 cycles ( +- 0.45% )
> 869,139,445,070 instructions ( +- 0.00% )
>
> 245.337510637 seconds time elapsed ( +- 0.49% )
>
>
> The speed up seems to be mainly in less cycles spent in servicing
> page faults:
>
> current code:
> 4.44% 0.01% perf.old [kernel.kallsyms] [k] page_fault
>
> with patches:
> 1.45% 0.00% perf [kernel.kallsyms] [k] page_fault
>
> current code (faults event):
> 6,643,807 faults ( +- 0.36% )
>
> with patches (faults event):
> 2,214,756 faults ( +- 3.03% )
>
>
> Also now we have one of our big memory spender under control
> and the ordered events queue code is put in separated object
> with clear interface ready to be used by another command
> like script.
>
> Also reachable in here:
> git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
> perf/core_ordered_events
>

I've skimmed through the patches. What happens if you are in the middle
of a round and the max queue size is reached?

I need to find some time for a detailed review, and to run through some
stress case scenarios. e.g., a couple that come to mind
perf sched record -- perf bench sched pipe
perf kvm record while booting a nested VM which causes a lot of VMEXITs

David



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