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Date:   Tue, 19 Jan 2021 12:11:58 +0900
From:   Namhyung Kim <>
To:     Andi Kleen <>
Cc:     Peter Zijlstra <>,
        Arnaldo Carvalho de Melo <>,
        Jiri Olsa <>, Ingo Molnar <>,
        Mark Rutland <>,
        Alexander Shishkin <>,
        LKML <>,
        Stephane Eranian <>,
        Ian Rogers <>,
        Alexey Alexandrov <>
Subject: Re: [PATCH] perf/core: Emit PERF_RECORD_LOST for pinned events

Hi Andi,

On Tue, Jan 19, 2021 at 11:47 AM Andi Kleen <> wrote:
> > > 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.

A problem is that we can have more than one event that failed.

In my understanding, we keep the lost count and add a LOST event
when there's a space later.  So probably we can keep a list of the
failed events and do similar for each event.  Or just use a single
event to notify some number of events were failed.


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