linux-kernel - Re: [patch 31/35] fs: icache per-zone inode LRU

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Date:	Wed, 20 Oct 2010 12:29:44 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Nick Piggin <npiggin@...nel.dk>
Cc:	kosaki.motohiro@...fujitsu.com, Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [patch 31/35] fs: icache per-zone inode LRU

> On Wed, Oct 20, 2010 at 12:14:32PM +0900, KOSAKI Motohiro wrote:
> > > On Tue, Oct 19, 2010 at 02:42:47PM +1100, npiggin@...nel.dk wrote:
> > > Anyway, my main point is that tying the LRU and shrinker scaling to
> > > the implementation of the VM is a one-off solution that doesn't work
> > > for generic infrastructure. Other subsystems need the same
> > > large-machine scaling treatment, and there's no way we should be
> > > tying them all into the struct zone. It needs further abstraction.
> > 
> > I'm not sure what data structure is best. I can only say current
> > zone unawareness slab shrinker might makes following sad scenario.
> > 
> >  o DMA zone shortage invoke and plenty icache in NORMAL zone dropping
> >  o NUMA aware system enable zone_reclaim_mode, but shrink_slab() still
> >    drop unrelated zone's icache
> > 
> > both makes performance degression. In other words, Linux does not have
> > flat memory model. so, I don't think Nick's basic concept is wrong. 
> > It's straight forward enhancement. but if it don't fit current shrinkers,
> > I'd like to discuss how to make better data structure.
> > 
> > 
> > 
> > and I have dump question (sorry, I don't know xfs at all). current
> > xfs_mount is below.
> > 
> > typedef struct xfs_mount {
> >  ...
> >         struct shrinker         m_inode_shrink; /* inode reclaim shrinker */
> > } xfs_mount_t;
> > 
> > 
> > Do you mean xfs can't convert shrinker to shrinker[ZONES]? If so, why?
> 
> Well if XFS were to use per-ZONE shrinkers, it would remain with a
> single shrinker context per-sb like it has now, but it would divide
> its object management into per-zone structures.

Oops, my fault ;)
Yes, my intention is converting mp->m_perag_tree to per-zone.

Thanks fix me.


> 
> For subsystems that aren't important, don't take much memory or have
> much reclaim throughput, they are free to ignore the zone argument
> and keep using the global input to the shrinker.
> 



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