From: Peter Zijlstra <peterz@infradead.org>
To: kan.liang@linux.intel.com
Cc: mingo@redhat.com, acme@kernel.org, linux-kernel@vger.kernel.org,
eranian@google.com, ak@linux.intel.com
Subject: Re: [RESEND PATCH V3] perf/x86: Consider pinned events for group validation
Date: Fri, 17 Jan 2020 09:58:41 +0100 [thread overview]
Message-ID: <20200117085841.GW2827@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1579201225-178031-1-git-send-email-kan.liang@linux.intel.com>
On Thu, Jan 16, 2020 at 11:00:25AM -0800, kan.liang@linux.intel.com wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> perf stat -M metrics relies on weak groups to reject unschedulable
> groups and run them as non-groups.
> This uses the group validation code in the kernel. Unfortunately
> that code doesn't take pinned events, such as the NMI watchdog, into
> account. So some groups can pass validation, but then later still
> never schedule.
>
> For example,
>
> $echo 1 > /proc/sys/kernel/nmi_watchdog
> $perf stat -M Page_Walks_Utilization
>
> Performance counter stats for 'system wide':
>
> <not counted> itlb_misses.walk_pending
> (0.00%)
> <not counted> dtlb_load_misses.walk_pending
> (0.00%)
> <not counted> dtlb_store_misses.walk_pending
> (0.00%)
> <not counted> ept.walk_pending
> (0.00%)
> <not counted> cycles
> (0.00%)
>
> 1.176613558 seconds time elapsed
More unreadable mess.
next prev parent reply other threads:[~2020-01-17 8:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 19:00 [RESEND PATCH V3] perf/x86: Consider pinned events for group validation kan.liang
2020-01-17 8:58 ` Peter Zijlstra [this message]
2020-01-17 9:13 ` Peter Zijlstra
2020-01-17 16:22 ` Andi Kleen
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