From: William Lee Irwin III <wli@holomorphy.com>
To: Brent Casavant <bcasavan@sgi.com>
Cc: Andrew Morton <akpm@osdl.org>, linux-mm@kvack.org
Subject: Re: Scaling problem with shmem_sb_info->stat_lock
Date: Wed, 28 Jul 2004 16:53:34 -0700 [thread overview]
Message-ID: <20040728235334.GF2334@holomorphy.com> (raw)
In-Reply-To: <Pine.SGI.4.58.0407281821040.33392@kzerza.americas.sgi.com>
On Wed, Jul 28, 2004 at 06:40:40PM -0500, Brent Casavant wrote:
> Well, it's really not even a common workload for tmpfs-backed-shm, where
> common means "non-HPC". Where SGI ran into this problem is with MPI
> startup. Our workaround at this time is to replace one large /dev/zero
> mapping shared amongst many forked processes (e.g. one process per CPU)
> with a bunch of single-page mappings of the same total size. This
> apparently has the effect of breaking the mapping up into multiple inodes,
> and reduces contention for any particular inode lock.
> But that's an ugly hack, and we really want to get rid of it. I may be
> talking out my rear, but I suspect that this will cause issues elsewhere
> (e.g. lots of tiny VM regions to track, which can be painful at
> fork/exec/exit time [if my IRIX experience serves me well]). I can look
> into the specifics of the workaround and probably provide numbers if
> anyone is really interested in such things at this point.
I'm very interested. I have similar issues with per-inode locks in other
contexts. This one is bound to factor in as well.
-- wli
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next prev parent reply other threads:[~2004-07-28 23:53 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-12 21:11 Scaling problem with shmem_sb_info->stat_lock Brent Casavant
2004-07-12 21:55 ` William Lee Irwin III
2004-07-12 22:42 ` Brent Casavant
2004-07-13 19:56 ` Brent Casavant
2004-07-13 20:41 ` Hugh Dickins
2004-07-13 21:35 ` Brent Casavant
2004-07-13 22:50 ` William Lee Irwin III
2004-07-13 22:22 ` William Lee Irwin III
2004-07-13 22:27 ` Brent Casavant
2004-07-28 9:26 ` Andrew Morton
2004-07-28 9:59 ` William Lee Irwin III
2004-07-28 22:21 ` Brent Casavant
2004-07-28 23:05 ` Andrew Morton
2004-07-28 23:40 ` Brent Casavant
2004-07-28 23:53 ` William Lee Irwin III [this message]
2004-07-28 23:53 ` William Lee Irwin III
2004-07-29 14:54 ` Brent Casavant
2004-07-29 19:58 ` Hugh Dickins
2004-07-29 21:21 ` Brent Casavant
2004-07-29 21:51 ` Brent Casavant
2004-07-30 1:00 ` William Lee Irwin III
2004-07-30 21:40 ` Brent Casavant
2004-07-30 23:34 ` Paul Jackson
2004-07-31 3:37 ` Ray Bryant
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