From: Andrew Morton <akpm@osdl.org>
To: Nick Piggin <piggin@cyberone.com.au>
Cc: nathans@sgi.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-xfs@oss.sgi.com
Subject: Re: Page cache write performance issue
Date: Wed, 13 Oct 2004 01:39:41 -0700 [thread overview]
Message-ID: <20041013013941.49693816.akpm@osdl.org> (raw)
In-Reply-To: <416CE423.3000607@cyberone.com.au>
Nick Piggin <piggin@cyberone.com.au> wrote:
>
> Andrew probably has better ideas.
uh, is this an ia32 highmem box?
If so, you've hit the VM sour spot. That 128M highmem zone gets 100%
filled with dirty pages and we end up doing a ton of writeout off the page
LRU. And we do that while `dd' is cheerfully writing to a totally
different part of the disk via balance_dirty_pages(). Seekstorm ensues.
Although last time I looked (a long time ago) the slowdown was only 2:1 -
perhaps your disk is in writethrough mode??
Basically, *any* other config is fine. 896MB and below, 1.5GB and above.
I could well understand that a minor kswapd tweak would make this bad
situation worse. Making the dirty ratios really small (dirty_ratio less
than the 128MB) should make it go away.
If it's not ia32 then dunno.
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next prev parent reply other threads:[~2004-10-13 8:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-13 5:44 Nathan Scott
2004-10-13 6:19 ` Andrew Morton
2004-10-13 6:39 ` Nathan Scott
2004-10-13 7:02 ` Andrew Morton
2004-10-13 7:23 ` Nathan Scott
2004-10-13 8:15 ` Nick Piggin
2004-10-13 8:39 ` Andrew Morton [this message]
2004-10-14 0:53 ` Nathan Scott
2004-10-14 3:20 ` Andrew Morton
2004-10-14 7:16 ` Nathan Scott
2004-10-14 7:31 ` Nick Piggin
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