From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>,
v9fs-developer@lists.sourceforge.net,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [RFC][PATCH] 9p: add readahead support for loose mode
Date: Sun, 16 Sep 2007 22:16:06 +0200 [thread overview]
Message-ID: <20070916221606.065e449f@lappy> (raw)
In-Reply-To: <20070915034126.cd2c2073.akpm@linux-foundation.org>
On Sat, 15 Sep 2007 03:41:26 -0700 Andrew Morton
<akpm@linux-foundation.org> wrote:
> eww, kmap. Large amounts of them, apparently.
>
> Be aware that kmap is a) slow and b) deadlockable. The latter happens when
> multiple tasks want to take more than one kmap simultaneously: they all
> wait for someone else to release one. Your code here seems especially
> vulnerable to this.
>
> Nick had a kmap-speedup patchset a while back which addressed a) but I
> don't know if it addressed the deadlock. But that patch seemed to die.
That would've been me.
What I did to address b) is to pre-allocate each kmap user a second
kmap slot. Of course this isn't water-tight either.
These patches are part of -rt, I could respin against mainline if there
is interest.
prev parent reply other threads:[~2007-09-16 20:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-14 16:02 [RFC][PATCH] 9p: add readahead support for loose mode Eric Van Hensbergen
2007-09-15 10:41 ` Andrew Morton
2007-09-16 20:16 ` Peter Zijlstra [this message]
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