linux-kernel - Re: balance storm

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Date:	Mon, 26 May 2014 19:49:10 +0800
From:	Libo Chen <libo.chen@...wei.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
CC:	<tglx@...utronix.de>, <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"Li Zefan" <lizefan@...wei.com>, <peterz@...radead.org>
Subject: Re: balance storm

On 2014/5/26 15:56, Mike Galbraith wrote:
> On Mon, 2014-05-26 at 11:04 +0800, Libo Chen wrote: 
>> hi,
>>     my box has 16 cpu (E5-2658,8 core, 2 thread per core), i did a test on
>> 3.4.24stable, startup 50 same process, every process is sample:
>>
>>  	#include <unistd.h>
>>
>>  	int main()
>>  	{
>>           	for (;;)
>>           	{
>>                   	unsigned int i = 0;
>>                  	 while (i< 100){
>>                      	 i++;
>>                   	}
>>                   	usleep(100);
>>           	}
>>
>>          	 return 0;
>>   	}
>>
>> the result is process uses 15% cpu time, perf tool shows 70w migrations in 5 second.
> 
> My 8 socket 64 core DL980 running 256 copies (3.14-rt5) munches ~4%/copy
> per top, and does roughly 1 sh*tload migrations, nano-work loop or not.
> Turn SD_SHARE_PKG_RESOURCES off at MC (not a noop here), and consumption
> drops to ~2%/copy, and migrations ('course) mostly go away.

how to turn off SD_SHARE_PKG_RESOURCES in userspace ?

> 
> vogelweide:/abuild/mike/:[0]# perf stat -a -e sched:sched_migrate_task -- sleep 5
> 
>  Performance counter stats for 'system wide':
> 
>               3108      sched:sched_migrate_task                                    
> 
>        5.001367910 seconds time elapsed
> 
> (turns SD_SHARE_PKG_RESOURCES back on)
> 
> vogelweide:/abuild/mike/:[0]# perf stat -a -e sched:sched_migrate_task -- sleep 5
> 
>  Performance counter stats for 'system wide':
> 
>            4182334      sched:sched_migrate_task                                    
> 
>        5.001365023 seconds time elapsed
> 
> vogelweide:/abuild/mike/:[0]# 
> 
> 
> 


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