Date: Fri, 19 Mar 2004 10:03:11 -0800
From: Andrew Morton <akpm@osdl.org>
To: dipankar@in.ibm.com
Cc: tiwai@suse.de, andrea@suse.de, mjy@geizhals.at,
       linux-kernel@vger.kernel.org
Subject: Re: CONFIG_PREEMPT and server workloads
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Dipankar Sarma <dipankar@in.ibm.com> wrote:
>
> On Thu, Mar 18, 2004 at 10:10:06PM -0800, Andrew Morton wrote:
>  > The worst-case latency is during umount, fs/inode.c:invalidate_list() when
>  > the filesystem has a zillion inodes in icache.  Measured 250 milliseconds
>  > on a 256MB 2.7GHz P4 here.   OK, so don't do that.
>  > 
>  > The unavoidable worst case is in the RCU callbacks for dcache shrinkage -
>  > I've seen 25 millisecond holdoffs on the above machine during filesystem
>  > stresstests when RCU is freeing a huge number of dentries in softirq
>  > context.
> 
>  What filesystem stresstest was that ? 

Something which creates a lot of slab, and a bit of memory pressure
basically.  Such as make-teeny-files from
http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz
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