linux-kernel - Re: [PATCH] mm: disallow direct reclaim page writeback

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Message-Id: <20100414145056.D147.A69D9226@jp.fujitsu.com>
Date:	Wed, 14 Apr 2010 14:54:14 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Dave Chinner <david@...morbit.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Chris Mason <chris.mason@...cle.com>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] mm: disallow direct reclaim page writeback

> On Wed, Apr 14, 2010 at 01:59:45PM +0900, KAMEZAWA Hiroyuki wrote:
> > On Wed, 14 Apr 2010 11:40:41 +1000
> > Dave Chinner <david@...morbit.com> wrote:
> > 
> > >  50)     3168      64   xfs_vm_writepage+0xab/0x160 [xfs]
> > >  51)     3104     384   shrink_page_list+0x65e/0x840
> > >  52)     2720     528   shrink_zone+0x63f/0xe10
> > 
> > A bit OFF TOPIC.
> > 
> > Could you share disassemble of shrink_zone() ?
> > 
> > In my environ.
> > 00000000000115a0 <shrink_zone>:
> >    115a0:       55                      push   %rbp
> >    115a1:       48 89 e5                mov    %rsp,%rbp
> >    115a4:       41 57                   push   %r15
> >    115a6:       41 56                   push   %r14
> >    115a8:       41 55                   push   %r13
> >    115aa:       41 54                   push   %r12
> >    115ac:       53                      push   %rbx
> >    115ad:       48 83 ec 78             sub    $0x78,%rsp
> >    115b1:       e8 00 00 00 00          callq  115b6 <shrink_zone+0x16>
> >    115b6:       48 89 75 80             mov    %rsi,-0x80(%rbp)
> > 
> > disassemble seems to show 0x78 bytes for stack. And no changes to %rsp
> > until retrun.
> 
> I see the same. I didn't compile those kernels, though. IIUC,
> they were built through the Ubuntu build infrastructure, so there is
> something different in terms of compiler, compiler options or config
> to what we are both using. Most likely it is the compiler inlining,
> though Chris's patches to prevent that didn't seem to change the
> stack usage.
> 
> I'm trying to get a stack trace from the kernel that has shrink_zone
> in it, but I haven't succeeded yet....

I also got 0x78 byte stack usage. Umm.. Do we discussed real issue now?




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