linux-kernel - Re: balance storm

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Date:	Tue, 27 May 2014 10:12:39 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Libo Chen <libo.chen@...wei.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 Tue, 2014-05-27 at 15:44 +0800, Libo Chen wrote: 
> On 2014/5/26 22:03, Mike Galbraith wrote:
> > On Mon, 2014-05-26 at 19:49 +0800, Libo Chen wrote:
> > 
> >> how to turn off SD_SHARE_PKG_RESOURCES in userspace ?
> > 
> > I use a script Ingo gave me years and years ago to
> > twiddle /proc/sys/kernel/sched_domain/cpuN/domainN/flags domain wise.
> > Doing that won't do you any good without a handler to build/tear down
> > sd_llc when you poke at flags though.  You can easily add a sched
> > feature to play with it.
> 
> 
> I make a simple script：
> 
>    for ((i=0;i<=15;i++))
>    do
>            echo 4143 > /proc/sys/kernel/sched_domain/cpu$i/domain1/flags
>    done
> 
> In our kernel  SD_SHARE_PKG_RESOURCE is 0x0200, the original flag value is 4655,
> domain1's name is MC.
> 
> but migrations event doesn't reduce like yours, what problem?  I wouldn't like
> recompile kernel :(

Hm, I thought you were a kernel hacker, but guess not since that would
be a really weird thing for a kernel hacker to say :)  Problem is that
there's no handler in your kernel to convert your flag poking to sd_llc
poking.

I could send you a patchlet, but that ain't gonna work, neither that nor
the commit I pointed out will seep into the kernel via osmosis.  There
should be a kernel hacker somewhere near you, look down the hall by the
water cooler, when you find one, he/she should be able to help.

-Mike

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