linux-kernel - Re: [PATCH/RFC 12/16] perf tools: Reduce lock contention when processing events

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Message-ID: <20151214084303.GA17701@krava.brq.redhat.com>
Date:	Mon, 14 Dec 2015 09:43:04 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH/RFC 12/16] perf tools: Reduce lock contention when
 processing events

On Thu, Dec 10, 2015 at 04:53:31PM +0900, Namhyung Kim wrote:
> When multi-thread is enabled, the machine->threads_lock is contented
> as all worker threads try to grab the writer lock using the
> machine__findnew_thread().  Usually, the thread they're looking for is
> in the tree so they only need the reader lock though.
> 
> Thus try machine__find_thread() first, and then fallback to the
> 'findnew' API.  This will improve the performance.

found one other place, but I guess you chose those
based on profiling the contention?

parent lookup in machine__process_fork_event

jirka
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