linux-kernel - Re: [PATCH] perf, tools: Fall weak group back even for EBADF

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Date:   Wed, 6 Sep 2017 13:52:13 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] perf, tools: Fall weak group back even for EBADF

On Tue, Sep 05, 2017 at 02:13:24PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> It's not possible to run a package event and a per cpu event in
> the same group. This is used by some of the power metrics.
> They work correctly when not using a group.
> 
> Normally weak groups should handle that, but in this case EBADF
> is returned instead of the normal EINVAL.
> 
> strace -e perf_event_open ./perf stat -v -e '{cstate_pkg/c2-residency/,msr/tsc/}:W' -a sleep 1
> Using CPUID GenuineIntel-6-3E
> perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, PERF_FLAG_FD_CLOEXEC) = -1 EINVAL (Invalid argument)
> perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
> perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
> perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
> perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = 3
> perf_event_open({type=0x7 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, 3, 0) = 4
> perf_event_open({type=0x7 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 1, 0, 0) = -1 EBADF (Bad file descriptor)
> 
> and perf errors out.
> 
> Make weak groups trigger a fall back for EBADF too. Then this case works correctly:
> 
> $ ./perf stat -v -e '{cstate_pkg/c2-residency/,msr/tsc/}:W' -a sleep 1
> Using CPUID GenuineIntel-6-3E
> Weak group for cstate_pkg/c2-residency//2 failed
> cstate_pkg/c2-residency/: 476709882 1000598460 1000598460
> msr/tsc/: 39625837911 12007369110 12007369110
> 
>  Performance counter stats for 'system wide':
> 
>        476,709,882      cstate_pkg/c2-residency/
>     39,625,837,911      msr/tsc/
> 
>        1.000697588 seconds time elapsed
> 
> This fixes perf stat -M Power ...
> 
> $ ./perf stat -M Power --metric-only -a sleep 1
> 
>  Performance counter stats for 'system wide':
> 
> Turbo_Utilization    C3_Core_Residency    C6_Core_Residency    C7_Core_Residency    C2_Pkg_Residency     C3_Pkg_Residency     C6_Pkg_Residency     C7_Pkg_Residency
>      1.0                 0.7                30.0                 0.0                 0.9                 0.1                 0.4                 0.0
> 
>        1.001240740 seconds time elapsed
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

seems ok me

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka