linux-kernel - Re: [PATCH] perf/core: generate overflow signal when samples are dropped (WAS: Re: [REGRESSION] perf/core: PMU interrupts dropped if we entered the kernel in the "skid" region)

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Message-ID: <20170704094602.dgrdwydui3wimf2s@hirez.programming.kicks-ass.net>
Date:   Tue, 4 Jul 2017 11:46:02 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Kyle Huey <me@...ehuey.com>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        "Jin, Yao" <yao.jin@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>, stable@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>, acme@...nel.org,
        jolsa@...nel.org, kan.liang@...el.com,
        Will Deacon <will.deacon@....com>, gregkh@...uxfoundation.org,
        Robert O'Callahan <robert@...llahan.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf/core: generate overflow signal when samples are
 dropped (WAS: Re: [REGRESSION] perf/core: PMU interrupts dropped if we
 entered the kernel in the "skid" region)

On Tue, Jul 04, 2017 at 10:33:45AM +0100, Mark Rutland wrote:

> > That said, with a per-cpu event the TID sample value is indeed subject
> > to skid like you describe.
> 
> For per-cpu events, does that matter? Those don't have TID filters in
> the first place, no?

eBPF can do all sorts I suppose.

But yes, at some point you just have to give up, there's only so much
one can do.