From: Nick Piggin <piggin@cyberone.com.au>
To: Nathan Scott <nathans@sgi.com>
Cc: Andrew Morton <akpm@osdl.org>,
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 18:15:31 +1000 [thread overview]
Message-ID: <416CE423.3000607@cyberone.com.au> (raw)
In-Reply-To: <20041013172352.B4917536@wobbly.melbourne.sgi.com>
Nathan Scott wrote:
>On Wed, Oct 13, 2004 at 12:02:06AM -0700, Andrew Morton wrote:
>
>>Well something else if fishy: how can you possibly achieve only 4MB/sec?
>>
>
>These are 1K writes too remember, so it feels a bit like we
>write 'em out one at a time, sync (though no O_SYNC, or fsync,
>or such involved here). This is on an i686, so 4K pages, and
>using 4K filesystem blocksizes (both xfs and ext2).
>
>
Still shouldn't cause such a big slowdown. Seems like they
might be getting written off the end of the page reclaim
LRU (although in that case it is a bit odd that increasing
the dirty thresholds are improving performance).
I don't think we have any vmscan metrics for this... kswapd
definitely has become more active in 2.6.9-rc. If you're stuck
for ideas, try editing mm/vmscan.c:may_write_to_queue - comment
out the if(current_is_kswapd()) check.
It is a long shot though. Andrew probably has better ideas.
WARNING: multiple messages have this Message-ID (diff)
From: Nick Piggin <piggin@cyberone.com.au>
To: Nathan Scott <nathans@sgi.com>
Cc: Andrew Morton <akpm@osdl.org>,
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 18:15:31 +1000 [thread overview]
Message-ID: <416CE423.3000607@cyberone.com.au> (raw)
In-Reply-To: <20041013172352.B4917536@wobbly.melbourne.sgi.com>
Nathan Scott wrote:
>On Wed, Oct 13, 2004 at 12:02:06AM -0700, Andrew Morton wrote:
>
>>Well something else if fishy: how can you possibly achieve only 4MB/sec?
>>
>
>These are 1K writes too remember, so it feels a bit like we
>write 'em out one at a time, sync (though no O_SYNC, or fsync,
>or such involved here). This is on an i686, so 4K pages, and
>using 4K filesystem blocksizes (both xfs and ext2).
>
>
Still shouldn't cause such a big slowdown. Seems like they
might be getting written off the end of the page reclaim
LRU (although in that case it is a bit odd that increasing
the dirty thresholds are improving performance).
I don't think we have any vmscan metrics for this... kswapd
definitely has become more active in 2.6.9-rc. If you're stuck
for ideas, try editing mm/vmscan.c:may_write_to_queue - comment
out the if(current_is_kswapd()) check.
It is a long shot though. Andrew probably has better ideas.
--
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next prev parent reply other threads:[~2004-10-13 8:15 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-13 5:44 Page cache write performance issue Nathan Scott
2004-10-13 5:44 ` Nathan Scott
2004-10-13 6:19 ` Andrew Morton
2004-10-13 6:19 ` Andrew Morton
2004-10-13 6:39 ` Nathan Scott
2004-10-13 6:39 ` Nathan Scott
2004-10-13 7:02 ` Andrew Morton
2004-10-13 7:02 ` Andrew Morton
2004-10-13 7:23 ` Nathan Scott
2004-10-13 7:23 ` Nathan Scott
2004-10-13 8:15 ` Nick Piggin [this message]
2004-10-13 8:15 ` Nick Piggin
2004-10-13 8:39 ` Andrew Morton
2004-10-13 8:39 ` Andrew Morton
2004-10-14 0:53 ` Nathan Scott
2004-10-14 0:53 ` Nathan Scott
2004-10-14 3:20 ` Andrew Morton
2004-10-14 3:20 ` Andrew Morton
2004-10-14 7:16 ` Nathan Scott
2004-10-14 7:16 ` Nathan Scott
2004-10-14 7:31 ` Nick Piggin
2004-10-14 7:31 ` Nick Piggin
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