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From: Daniel Phillips <phillips@arcor.de>
To: Andrew Morton <akpm@zip.com.au>
Subject: Re: [RFC] [PATCH] Include LRU in page count
Date: Mon, 2 Sep 2002 01:33:06 +0200
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Cc: Christian Ehrhardt <ehrhardt@mathematik.uni-ulm.de>,
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On Monday 02 September 2002 01:08, Andrew Morton wrote:
> Daniel Phillips wrote:
> > Note that I changed the spin_lock in page_cache_release to a trylock, maybe
> > it's worth checking out the effect on contention.  With a little head
> > scratching we might be able to get rid of the spin_lock in lru_cache_add as
> > well.  That leaves (I think) just the two big scan loops.  I've always felt
> > it's silly to run more than one of either at the same time anyway.
> 
> No way.  Take a look at http://samba.org/~anton/linux/2.5.30/
> 
> That's 8-way power4, the workload is "dd from 7 disks
> dd if=/dev/sd* of=/dev/null bs=1024k".
> 
> The CPU load in this situation was dominated by the VM.  The LRU list and page
> reclaim.  Spending more CPU in lru_cache_add() than in copy_to_user() is
> pretty gross.

Are we looking at the same thing?  The cpu load there is dominated by cpu_idle,
89%.  Anyway, if your point is that it makes sense to run shrink_cache or
refill_inactive in parallel, I don't see it because they'll serialize on the
lru lock anyway.  What would make sense is to make shink_cache nonblocking.

> My approach was to keep the existing design and warm it up, rather than to
> redesign.

Yup.

-- 
Daniel
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