linux-kernel - Re: [PATCH] perf/core: Emit PERF_RECORD

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Message-ID: <20210119024657.GA3526@tassilo.jf.intel.com>
Date:   Mon, 18 Jan 2021 18:46:57 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>,
        Alexey Alexandrov <aalexand@...gle.com>
Subject: Re: [PATCH] perf/core: Emit PERF_RECORD_LOST for pinned events

> > I don't think I object to having an even in the stream, but your LOST
> > event is unfortunate in that it itself can get lost when there's no
> > space in the buffer (which arguably is unlikely, but still).
> >
> > So from that point of view, I think overloading LOST is not so very nice
> > for this.
> 
> But anything can get lost in case of no space.
> Do you want to use something other than the LOST event?

Could always reserve the last entry in the ring buffer for a LOST event,
that would guarantee you can always get one out.

-Andi