linux-kernel - Re: [RFC] Limit the size of the pagecache

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Message-Id: <20070127030143.3059dbb0.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Sat, 27 Jan 2007 03:01:43 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	clameter@....com, aubreylee@...il.com, svaidy@...ux.vnet.ibm.com,
	nickpiggin@...oo.com.au, rgetz@...ckfin.uclinux.org,
	Michael.Hennerich@...log.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] Limit the size of the pagecache

On Fri, 26 Jan 2007 02:29:55 -0800
Andrew Morton <akpm@...l.org> wrote:

> On Wed, 24 Jan 2007 14:15:10 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > - One for stability
> >   When a customer constructs their detabase(Oracle), the system often goes to oom.
> >   This is because that the system cannot allocate DMA_ZOME memory for 32bit device.
> >   (USB or e100)
> >   Not allowing to use almost all pages as page cache (for temporal use) will be some help.
> >   (Note: construction DB on ext3....so all writes are serialized and the system couldn't
> >    free page cache.)
> 
> I'm surprised that any reasonable driver has a dependency on ZONE_DMA.  Are
> you sure?  Send full oom-killer output, please.
> 
> 
Our ia64 server's USB/e100 device uses 32bit-PCI, so sometimes OOM happens on DMA zone.
(ia64's ZONE_DMA is 0-4G area.)

But very sorry....I was confused.

I looked the issue above again and found ZONE_NORMAL/x86 was exhausted.

This was interesiting incident,

Constructing DB on 4Gb system has no problem.
Constructing DB on 8Gb system always causes OOM.

I asked the users to change DB's parameter. (this happened on RHEL4/linux-2.6.9 series)


> >   And...some customers want to keep memory Free as much as possible.
> >   99% memory usage makes insecure them ;)
> 
> Tell them to do "echo 3 > /proc/sys/vm/drop_caches", then wait three minutes?

Ah, maybe we can use it on RHEL5. We'll test it. thank you.

Thanks,
-Kamezawa



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