linux-kernel - Re: [PATCH 38/40] perf session: Handle index files generally

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Date:	Wed, 20 May 2015 09:05:12 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 38/40] perf session: Handle index files generally

Hi David,

On Tue, May 19, 2015 at 04:27:02PM -0600, David Ahern wrote:
> On 5/17/15 6:30 PM, Namhyung Kim wrote:
> >The current code assumes that the number of index item and cpu are
> >matched so it creates that number of threads.  But it's not the case
> >of non-system-wide session or data came from different machine.
> >
> >Just creates threads at most number of online cpus and process data.
> 
> -----8<-----
> 
> >@@ -1717,6 +1742,7 @@ int perf_session__process_events_mt(struct perf_session *session, void *arg)
> >  	int err, i, k;
> >  	int nr_index = session->header.nr_index;
> >  	u64 size = perf_data_file__size(file);
> >+	int nr_thread = sysconf(_SC_NPROCESSORS_ONLN);
> 
> It's not clear to me how this multi-threaded perf is going to work on large
> systems especially this patch if a system has holes in the active cpus. e.g,
> 
> # lscpu
> Architecture:          sparc64
> CPU op-mode(s):        32-bit, 64-bit
> Byte Order:            Big Endian
> CPU(s):                704
> On-line CPU(s) list: 32-63,128-223,256-351,384-479,576-831,864-927,960-1023
> Thread(s) per core:    12
> Core(s) per socket:    18
> Socket(s):             3
> NUMA node(s):          4
> NUMA node0 CPU(s):     32-63,128-223
> NUMA node1 CPU(s):     256-351,384-479
> NUMA node2 CPU(s):     576-767
> NUMA node3 CPU(s):     768-831,864-927,960-1023
> 
> So you are going to spawn 704 threads? Each thread handles a per-cpu buffer?

Oh, I need to add an option (and probably a config variable too) to
specify number of thread to run.

> 
> yes, I still need to find time to take if for a test drive; maybe by the end
> of the week.

Oh, it'd be very nice if you can test and share the numbers on such a
large machine.  I'll send the --num-thread option patch soon on top of
this series for you. :)

Thanks,
Namhyung


> 
> David
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