netdev - Re: [PATCH] kthread: NUMA aware kthread_create_on

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Message-ID: <20101129090510.GA15763@basil.fritz.box>
Date:	Mon, 29 Nov 2010 10:05:10 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>, Tejun Heo <tj@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] kthread: NUMA aware kthread_create_on_cpu()

On Mon, Nov 29, 2010 at 12:37:04AM +0100, Eric Dumazet wrote:
> Le lundi 29 novembre 2010 à 00:01 +0100, Andi Kleen a écrit :
> > On Sun, Nov 28, 2010 at 11:51:51PM +0100, Eric Dumazet wrote:
> > > > Also this messes up the policy of the caller process. You really
> > > > need to save/restore it.
> > > 
> > > Well, caller process duty is to create kthreads in a loop.
> > 
> > In this case any other allocations it may do
> >  are still on those
> > nodes.
> 
> As I said, it does only create_kthread() calls, and no "other
> allocations".

Code changes. Your current setup seems fragile (also
the static variable)

> > > > for the stack, so may be a larger patch.
> > > 
> > > I suggest arches that need slab to allocate kthread stacks do the
> > > appropriate changes, because I am not able to make them myself.
> > > 
> > > On x86, we use page allocator only, so NUMA mempolicy is used.
> > 
> > task_struct is always allocated from slab.
> 
> Hmm, I meant stack (the thing that might be trashed a lot in ksoftirqd),
> so it is included in struct thread_info

task_struct is quite hot too. Also your original mail said
task struct i believe.

> And got correct stacks. Are you sure we must use PREFERRED ?

Yes.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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