From: Dave Chinner <david@fromorbit.com>
To: Ed Tomlinson <edt@aei.ca>
Cc: npiggin@suse.de, Pekka Enberg <penberg@cs.helsinki.fi>,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
linux-mm@kvack.org, Andi Kleen <andi@firstfloor.org>,
linux-fsdevel@vger.kernel.org, Christoph Lameter <cl@linux.com>
Subject: Re: Defrag in shrinkers
Date: Mon, 17 May 2010 10:24:44 +1000 [thread overview]
Message-ID: <20100517002444.GJ8120@dastard> (raw)
In-Reply-To: <201005151308.18090.edt@aei.ca>
On Sat, May 15, 2010 at 01:08:17PM -0400, Ed Tomlinson wrote:
> On Friday 14 May 2010 16:36:03 Andi Kleen wrote:
> > Christoph Lameter <cl@linux.com> writes:
> >
> > > Would it also be possible to add some defragmentation logic when you
> > > revise the shrinkers? Here is a prototype patch that would allow you to
> > > determine the other objects sitting in the same page as a given object.
> > >
> > > With that I hope that you have enough information to determine if its
> > > worth to evict the other objects as well to reclaim the slab page.
> >
> > I like the idea, it would be useful for the hwpoison code too,
> > when it tries to clean a page.
>
> If this is done generally we probably want to retune the 'pressure' put on the slab. The
> whole reason for the callbacks was to keep the 'pressure on the slab proportional to the
> memory pressure (scan rate).
I don't see that defrag based reclaim changes the concept of
pressure at all. As long as reclaim follows the nr_to_scan
guideline, then it doesn't matter if we do reclaim from the LRU or
reclaim from a list provided by the slab cache....
FWIW, one thing that would be necessary, I think, is to avoid defrag
until a certain level of fragmentation has occurred - we should do
LRU-based reclaim as much as possible, and only trigger defrag-style
reclaim once we hit a trigger (e.g. once the slab is 25% partial
pages).
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
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xfs@oss.sgi.com
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Ed Tomlinson <edt@aei.ca>
Cc: Andi Kleen <andi@firstfloor.org>,
Christoph Lameter <cl@linux.com>,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Pekka Enberg <penberg@cs.helsinki.fi>,
npiggin@suse.de
Subject: Re: Defrag in shrinkers
Date: Mon, 17 May 2010 10:24:44 +1000 [thread overview]
Message-ID: <20100517002444.GJ8120@dastard> (raw)
In-Reply-To: <201005151308.18090.edt@aei.ca>
On Sat, May 15, 2010 at 01:08:17PM -0400, Ed Tomlinson wrote:
> On Friday 14 May 2010 16:36:03 Andi Kleen wrote:
> > Christoph Lameter <cl@linux.com> writes:
> >
> > > Would it also be possible to add some defragmentation logic when you
> > > revise the shrinkers? Here is a prototype patch that would allow you to
> > > determine the other objects sitting in the same page as a given object.
> > >
> > > With that I hope that you have enough information to determine if its
> > > worth to evict the other objects as well to reclaim the slab page.
> >
> > I like the idea, it would be useful for the hwpoison code too,
> > when it tries to clean a page.
>
> If this is done generally we probably want to retune the 'pressure' put on the slab. The
> whole reason for the callbacks was to keep the 'pressure on the slab proportional to the
> memory pressure (scan rate).
I don't see that defrag based reclaim changes the concept of
pressure at all. As long as reclaim follows the nr_to_scan
guideline, then it doesn't matter if we do reclaim from the LRU or
reclaim from a list provided by the slab cache....
FWIW, one thing that would be necessary, I think, is to avoid defrag
until a certain level of fragmentation has occurred - we should do
LRU-based reclaim as much as possible, and only trigger defrag-style
reclaim once we hit a trigger (e.g. once the slab is 25% partial
pages).
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Ed Tomlinson <edt@aei.ca>
Cc: Andi Kleen <andi@firstfloor.org>,
Christoph Lameter <cl@linux.com>,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Pekka Enberg <penberg@cs.helsinki.fi>,
npiggin@suse.de
Subject: Re: Defrag in shrinkers
Date: Mon, 17 May 2010 10:24:44 +1000 [thread overview]
Message-ID: <20100517002444.GJ8120@dastard> (raw)
In-Reply-To: <201005151308.18090.edt@aei.ca>
On Sat, May 15, 2010 at 01:08:17PM -0400, Ed Tomlinson wrote:
> On Friday 14 May 2010 16:36:03 Andi Kleen wrote:
> > Christoph Lameter <cl@linux.com> writes:
> >
> > > Would it also be possible to add some defragmentation logic when you
> > > revise the shrinkers? Here is a prototype patch that would allow you to
> > > determine the other objects sitting in the same page as a given object.
> > >
> > > With that I hope that you have enough information to determine if its
> > > worth to evict the other objects as well to reclaim the slab page.
> >
> > I like the idea, it would be useful for the hwpoison code too,
> > when it tries to clean a page.
>
> If this is done generally we probably want to retune the 'pressure' put on the slab. The
> whole reason for the callbacks was to keep the 'pressure on the slab proportional to the
> memory pressure (scan rate).
I don't see that defrag based reclaim changes the concept of
pressure at all. As long as reclaim follows the nr_to_scan
guideline, then it doesn't matter if we do reclaim from the LRU or
reclaim from a list provided by the slab cache....
FWIW, one thing that would be necessary, I think, is to avoid defrag
until a certain level of fragmentation has occurred - we should do
LRU-based reclaim as much as possible, and only trigger defrag-style
reclaim once we hit a trigger (e.g. once the slab is 25% partial
pages).
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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next prev parent reply other threads:[~2010-05-17 0:22 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-14 7:24 [PATCH 0/5] Per-superblock shrinkers Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` [PATCH 1/5] inode: Make unused inode LRU per superblock Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` [PATCH 2/5] mm: add context argument to shrinker callback Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` [PATCH 3/5] superblock: introduce per-sb cache shrinker infrastructure Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` [PATCH 4/5] superblock: add filesystem shrinker operations Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` [PATCH 5/5] xfs: make use of new shrinker callout Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 7:24 ` Dave Chinner
2010-05-14 17:46 ` Defrag in shrinkers (was Re: [PATCH 0/5] Per-superblock shrinkers) Christoph Lameter
2010-05-14 17:46 ` Christoph Lameter
2010-05-14 17:46 ` Christoph Lameter
2010-05-14 20:36 ` Defrag in shrinkers Andi Kleen
2010-05-14 20:36 ` Andi Kleen
2010-05-14 20:36 ` Andi Kleen
2010-05-15 17:08 ` Ed Tomlinson
2010-05-15 17:08 ` Ed Tomlinson
2010-05-15 17:08 ` Ed Tomlinson
2010-05-17 0:24 ` Dave Chinner [this message]
2010-05-17 0:24 ` Dave Chinner
2010-05-17 0:24 ` Dave Chinner
2010-05-15 1:15 ` Defrag in shrinkers (was Re: [PATCH 0/5] Per-superblock shrinkers) Dave Chinner
2010-05-15 1:15 ` Dave Chinner
2010-05-15 1:15 ` Dave Chinner
2010-05-15 1:30 ` [PATCH 0/5] Per-superblock shrinkers Al Viro
2010-05-15 1:30 ` Al Viro
2010-05-15 1:30 ` Al Viro
2010-05-17 0:19 ` Dave Chinner
2010-05-17 0:19 ` Dave Chinner
2010-05-17 0:19 ` Dave Chinner
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