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Date:   Mon, 18 Jan 2021 18:46:57 -0800
From:   Andi Kleen <ak@linux.intel.com>
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@kernel.org>,
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        LKML <linux-kernel@vger.kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Ian Rogers <irogers@google.com>,
        Alexey Alexandrov <aalexand@google.com>
Subject: Re: [PATCH] perf/core: Emit PERF_RECORD_LOST for pinned events
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> > 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