From: Christoph Hellwig <hch@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Dave Hansen <haveblue@us.ibm.com>,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [PATCH 24/25] r/o bind mounts: track number of mount writers
Date: Mon, 24 Sep 2007 20:24:26 +0100 [thread overview]
Message-ID: <20070924192425.GA6629@infradead.org> (raw)
In-Reply-To: <20070924121035.8d8c6ce2.akpm@linux-foundation.org>
On Mon, Sep 24, 2007 at 12:10:35PM -0700, Andrew Morton wrote:
> > As we already say in various messages the percpu counters in here
> > look rather fishy. I'd recomment to take a look at the per-cpu
> > superblock counters in XFS as they've been debugged quite well
> > now and could probably be lifted into a generic library for this
> > kind of think. The code is mostly in fs/xfs/xfs_mount.c can
> > can be spotted by beeing under #ifdef HAVE_PERCPU_SB.
> >
> > It also handles cases like hotplug cpu nicely that this code
> > seems to work around by always iterating over all possible cpus
> > which might not be nice on a dual core laptop with a distro kernel
> > that also has to support big iron.
>
> hm. How come xfs invented a new version of percpu_counters?
This code actually predates the generic percpu_counters even if it
was merged to mainline later. Neither Dave who wrote it nor me
who reviewed it before it was merged thought of percpu_counters
probably. Then again this code is considerably more complex due
to features actually needed in a very hot fastpath.
parent reply other threads:[~2007-09-24 19:24 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20070924121035.8d8c6ce2.akpm@linux-foundation.org>]
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