Messages in this thread | | | From | "Zhu, DengCheng" <> | Subject | RE: [RFC PATCH 2/2] tools/perf: Make group_fd static and move its place in __perf_evsel__open() | Date | Wed, 26 Oct 2011 13:14:53 +0000 |
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> ________________________________________ > From: Arnaldo Carvalho de Melo [arnaldo.melo@gmail.com] on behalf of Arnaldo Carvalho de Melo [acme@ghostprotocols.net] > Sent: Wednesday, October 26, 2011 7:18 PM > To: Zhu, DengCheng > Cc: linux-kernel@vger.kernel.org; Peter Zijlstra; Paul Mackerras; Ingo Molnar > Subject: Re: [RFC PATCH 2/2] tools/perf: Make group_fd static and move its place in __perf_evsel__open() > > Em Wed, Oct 26, 2011 at 02:26:03PM +0800, Deng-Cheng Zhu escreveu: >> On 10/25/2011 11:23 PM, Arnaldo Carvalho de Melo wrote: >> >Em Mon, Oct 24, 2011 at 12:03:28PM -0200, Arnaldo Carvalho de Melo escreveu: >> >>Em Mon, Oct 24, 2011 at 06:57:00PM +0800, Deng-Cheng Zhu escreveu: >> >>>__perf_evsel__open() is called per event, it does not work for all the >> >>>grouped events at one time. So, currently group_fd will alway be -1 for > > <SNIP> > >> >>>+ static int group_fd = -1; >> >>> if (!evsel->cgrp) >> >>> pid = threads->map[thread]; > >> >>Lets not do it that way, using statics for this is humm, ugly, IMHO. > >> >Can you try this patch? > >> >I tested it with: > >> >[root@emilia ~]# perf top -e cycles -e instructions --group > >> Your patch does fix the group fd issue. But to get event grouping >> workable, the event state fix is still needed. Please see the discussion > > Can I have your "Reviewed-by:" or "Tested-by:" tag for this patch then?
Yes, you may add my:
Tested-by: Deng-Cheng Zhu <dczhu@mips.com>
>> here: http://www.spinics.net/lists/mips/msg42190.html > >> With _only_ your patch applied, I tested with the following commands on >> MIPS 74K (4 counters available in total): >> >> perf stat -g -e >> L1-dcache-load-misses,cycles,LLC-load-misses,iTLB-loads,instructions >> find / >/dev/null >> >> I tried to group up to 5 events in the hope of seeing NOSPC error. But >> the command didn't fail and output: >> >> Performance counter stats for 'find /': >> >> 9300823 L1-dcache-load-misses >> <not counted> cycles >> <not counted> LLC-load-misses >> <not counted> iTLB-loads >> <not counted> instructions >> >> 8.463207591 seconds time elapsed >> >> This is due to the event state check in validate_group() filtering out >> the grouped events in OFF state. They are in OFF state because we are >> running the command with the perf tool as opposed to attaching to an >> existing task: >> >> builtin-stat.c:create_perf_stat_counter(): >> >> if (target_pid == -1 && target_tid == -1) { >> attr->disabled = 1; >> attr->enable_on_exec = 1; >> } > > But they should be in OFF state only till the target program gets > exec'ed, right? >
Yes, or else event timestamps won't be updated on exec. That's why I came to a new idea in one of my MIPS perf-events patches (link provided above).
>> I suppose X86 has this issue too -- collect_events() in validate_group() >> won't do real work in the bottom half of the function. > > I'm testing that now.
As you can see from the test results in your another post, I think we see "not counted" because collect_events() in validate_group() does not do real work on events in OFF state. On x86 a patch may be needed in event init, but on MIPS (or ARM) I suppose the pmu and event state checks in validate_event() perhaps could be deleted...
Deng-Cheng
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