linux-kernel - Re: [PATCH 0/5] sched/debug: decouple sched_stat tracepoints from CONFIG

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Message-ID: <20160629102958.GC30927@twins.programming.kicks-ass.net>
Date:	Wed, 29 Jun 2016 12:29:58 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...hsingularity.net>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 0/5] sched/debug: decouple sched_stat tracepoints from
 CONFIG_SCHEDSTATS

On Tue, Jun 28, 2016 at 02:43:36PM +0200, Peter Zijlstra wrote:

> Yeah, its a bit of a pain in general...
> 
> A) perf stat --null --repeat 50 -- perf bench sched messaging -g 50 -l 5000 | grep "seconds time elapsed"
> B) perf stat --null --repeat 50 -- taskset 1 perf bench sched pipe | grep "seconds time elapsed"
> 
> 1) tip/master + 1-4
> 2) tip/master + 1-5
> 3) tip/master + 1-5 + below
> 
> 	1		2		3
> 
> A)	4.627767855	4.650429917	4.646208062
> 	4.633921933	4.641424424	4.612021058
> 	4.649536375	4.663144144	4.636815948
> 	4.630165619	4.649053552	4.613022902
> 
> B)	1.770732957	1.789534273	1.773334291
> 	1.761740716	1.795618428	1.773338681
> 	1.763761666	1.822316496	1.774385589
> 
> 
> From this it looks like patch 5 does hurt a wee bit, but we can get most
> of that back by reordering the structure a bit. The results seem
> 'stable' across rebuilds and reboots (I've pop'ed all patches and
> rebuild, rebooted and re-benched 1 at the end and obtained similar
> results).

Ha! So those numbers were with CONFIG_SCHEDSTAT=n :-/

1) above 1 (4 patches, CONFIG_SCHEDSTAT=n, sysctl=0)
2) 1 + CONFIG_SCHEDSTAT=y (sysctl=0)
3) 2 + sysctl=1
4) above 3 (6 patches) + CONFIG_SCHEDSTAT=y (sysctl=0)


	1		2		3		4

A)	4.620495664	4.788352823	4.862036428	4.623480512
	4.628800053	4.792622881	4.855325525	4.613553872
	4.611909507	4.794282178	4.850959761	4.613323142
	4.608379522	4.787300153	4.822439864	4.597903070

B)	1.765668026	1.788374847	1.877803100	1.827213170
	1.769379968	1.779881911	1.870091005	1.825335322
	1.765822150	1.786251610	1.885874745	1.828218761


Which looks good for hackbench, but still stinks for pipetest :/