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Date: Wed, 25 Mar 2015 08:41:07 -0600
From: David Ahern <david.ahern@oracle.com>
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To: Arnaldo Carvalho de Melo <acme@kernel.org>, Ingo Molnar <mingo@kernel.org>
CC: linux-kernel@vger.kernel.org, Frederic Weisbecker <fweisbec@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH] perf record: Allow poll timeout to be specified
References: <1427213388-127148-1-git-send-email-david.ahern@oracle.com> <20150324161210.GA8661@gmail.com> <20150324212120.GA12599@kernel.org> <20150325091147.GA1565@gmail.com> <20150325121425.GA13759@kernel.org>
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On 3/25/15 6:14 AM, Arnaldo Carvalho de Melo wrote:
> If David doesn't come up with something I'll probably will, as making
> 'trace' use the ordered_samples, like 'perf top' does (initially with
> some arbitrary reasonable poll timeout value), is a low hanging fruit to
> get those multi-CPU tracepoints sorted until I get something better in
> place...

I have thought about it. It needs to be an adaptive algorithm:
1. start at 100 msec.
2. Read the maps. How much data are there (not events, but data size)? 
3. Adjust poll timeout up or down with some heuristic -- maybe something 
similar to the algorithm perf-top uses for removing entries from the 
histograms.

That said, I still thinking giving the user control is not a crazy idea.

David