From: Chris Wilson <chris@chris-wilson.co.uk>
To: Dave Chinner <david@fromorbit.com>, glommer@parallels.com
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [PATCH 17/19] drivers: convert shrinkers to new count/scan API
Date: Wed, 28 Nov 2012 01:13:11 +0000 [thread overview]
Message-ID: <b94cdc$7i2bv3@fmsmga001.fm.intel.com> (raw)
In-Reply-To: <1354058086-27937-18-git-send-email-david@fromorbit.com>
On Wed, 28 Nov 2012 10:14:44 +1100, Dave Chinner <david@fromorbit.com> wrote:
> +/*
> + * XXX: (dchinner) This is one of the worst cases of shrinker abuse I've seen.
> + *
> + * i915_gem_purge() expects a byte count to be passed, and the minimum object
> + * size is PAGE_SIZE.
No, purge() expects a count of pages to be freed. Each pass of the
shrinker therefore tries to free a minimum of 128 pages.
> The shrinker doesn't work on bytes - it works on
> + * *objects*.
And I thought you were reviewing the shrinker API to be useful where a
single object may range between 4K and 4G.
> So it passes a nr_to_scan of 128 objects, which is interpreted
> + * here to mean "free 128 bytes". That means a single object will be freed, as
> + * the minimum object size is a page.
> + *
> + * But the craziest part comes when i915_gem_purge() has walked all the objects
> + * and can't free any memory. That results in i915_gem_shrink_all() being
> + * called, which idles the GPU and frees everything the driver has in it's
> + * active and inactive lists. It's basically hitting the driver with a great big
> + * hammer because it was busy doing stuff when something else generated memory
> + * pressure. This doesn't seem particularly wise...
> + */
As opposed to triggering an OOM? The choice was between custom code for
a hopefully rare code path in a situation of last resort, or first
implementing the simplest code that stopped i915 from starving the
system of memory.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
_______________________________________________
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xfs@oss.sgi.com
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WARNING: multiple messages have this Message-ID (diff)
From: Chris Wilson <chris@chris-wilson.co.uk>
To: Dave Chinner <david@fromorbit.com>, glommer@parallels.com
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, xfs@oss.sgi.com
Subject: Re: [PATCH 17/19] drivers: convert shrinkers to new count/scan API
Date: Wed, 28 Nov 2012 01:13:11 +0000 [thread overview]
Message-ID: <b94cdc$7i2bv3@fmsmga001.fm.intel.com> (raw)
In-Reply-To: <1354058086-27937-18-git-send-email-david@fromorbit.com>
On Wed, 28 Nov 2012 10:14:44 +1100, Dave Chinner <david@fromorbit.com> wrote:
> +/*
> + * XXX: (dchinner) This is one of the worst cases of shrinker abuse I've seen.
> + *
> + * i915_gem_purge() expects a byte count to be passed, and the minimum object
> + * size is PAGE_SIZE.
No, purge() expects a count of pages to be freed. Each pass of the
shrinker therefore tries to free a minimum of 128 pages.
> The shrinker doesn't work on bytes - it works on
> + * *objects*.
And I thought you were reviewing the shrinker API to be useful where a
single object may range between 4K and 4G.
> So it passes a nr_to_scan of 128 objects, which is interpreted
> + * here to mean "free 128 bytes". That means a single object will be freed, as
> + * the minimum object size is a page.
> + *
> + * But the craziest part comes when i915_gem_purge() has walked all the objects
> + * and can't free any memory. That results in i915_gem_shrink_all() being
> + * called, which idles the GPU and frees everything the driver has in it's
> + * active and inactive lists. It's basically hitting the driver with a great big
> + * hammer because it was busy doing stuff when something else generated memory
> + * pressure. This doesn't seem particularly wise...
> + */
As opposed to triggering an OOM? The choice was between custom code for
a hopefully rare code path in a situation of last resort, or first
implementing the simplest code that stopped i915 from starving the
system of memory.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
--
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WARNING: multiple messages have this Message-ID (diff)
From: Chris Wilson <chris@chris-wilson.co.uk>
To: Dave Chinner <david@fromorbit.com>, glommer@parallels.com
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, xfs@oss.sgi.com
Subject: Re: [PATCH 17/19] drivers: convert shrinkers to new count/scan API
Date: Wed, 28 Nov 2012 01:13:11 +0000 [thread overview]
Message-ID: <b94cdc$7i2bv3@fmsmga001.fm.intel.com> (raw)
In-Reply-To: <1354058086-27937-18-git-send-email-david@fromorbit.com>
On Wed, 28 Nov 2012 10:14:44 +1100, Dave Chinner <david@fromorbit.com> wrote:
> +/*
> + * XXX: (dchinner) This is one of the worst cases of shrinker abuse I've seen.
> + *
> + * i915_gem_purge() expects a byte count to be passed, and the minimum object
> + * size is PAGE_SIZE.
No, purge() expects a count of pages to be freed. Each pass of the
shrinker therefore tries to free a minimum of 128 pages.
> The shrinker doesn't work on bytes - it works on
> + * *objects*.
And I thought you were reviewing the shrinker API to be useful where a
single object may range between 4K and 4G.
> So it passes a nr_to_scan of 128 objects, which is interpreted
> + * here to mean "free 128 bytes". That means a single object will be freed, as
> + * the minimum object size is a page.
> + *
> + * But the craziest part comes when i915_gem_purge() has walked all the objects
> + * and can't free any memory. That results in i915_gem_shrink_all() being
> + * called, which idles the GPU and frees everything the driver has in it's
> + * active and inactive lists. It's basically hitting the driver with a great big
> + * hammer because it was busy doing stuff when something else generated memory
> + * pressure. This doesn't seem particularly wise...
> + */
As opposed to triggering an OOM? The choice was between custom code for
a hopefully rare code path in a situation of last resort, or first
implementing the simplest code that stopped i915 from starving the
system of memory.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
next prev parent reply other threads:[~2012-11-28 1:11 UTC|newest]
Thread overview: 163+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-27 23:14 [RFC, PATCH 00/19] Numa aware LRU lists and shrinkers Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 01/19] dcache: convert dentry_stat.nr_unused to per-cpu counters Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 02/19] dentry: move to per-sb LRU locks Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 03/19] dcache: remove dentries from LRU before putting on dispose list Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 04/19] mm: new shrinker API Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 05/19] shrinker: convert superblock shrinkers to new API Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-12-20 11:06 ` Glauber Costa
2012-12-20 11:06 ` Glauber Costa
2012-12-20 11:06 ` Glauber Costa
2012-12-21 1:46 ` Dave Chinner
2012-12-21 1:46 ` Dave Chinner
2012-12-21 10:17 ` Glauber Costa
2012-12-21 10:17 ` Glauber Costa
2012-12-21 10:17 ` Glauber Costa
2012-11-27 23:14 ` [PATCH 06/19] list: add a new LRU list type Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-28 16:10 ` Christoph Hellwig
2012-11-28 16:10 ` Christoph Hellwig
2012-11-28 16:10 ` Christoph Hellwig
2012-11-27 23:14 ` [PATCH 07/19] inode: convert inode lru list to generic lru list code Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 08/19] dcache: convert to use new lru list infrastructure Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 09/19] list_lru: per-node " Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-12-20 11:21 ` Glauber Costa
2012-12-20 11:21 ` Glauber Costa
2012-12-20 11:21 ` Glauber Costa
2012-12-21 1:54 ` Dave Chinner
2012-12-21 1:54 ` Dave Chinner
2013-01-16 19:21 ` Glauber Costa
2013-01-16 19:21 ` Glauber Costa
2013-01-16 19:21 ` Glauber Costa
2013-01-16 22:55 ` Dave Chinner
2013-01-16 22:55 ` Dave Chinner
2013-01-17 0:35 ` Glauber Costa
2013-01-17 0:35 ` Glauber Costa
2013-01-17 0:35 ` Glauber Costa
2013-01-17 4:22 ` Dave Chinner
2013-01-17 4:22 ` Dave Chinner
2013-01-17 18:21 ` Glauber Costa
2013-01-17 18:21 ` Glauber Costa
2013-01-17 18:21 ` Glauber Costa
2013-01-18 0:10 ` Dave Chinner
2013-01-18 0:10 ` Dave Chinner
2013-01-18 0:14 ` Glauber Costa
2013-01-18 0:14 ` Glauber Costa
2013-01-18 0:14 ` Glauber Costa
2013-01-18 8:11 ` Dave Chinner
2013-01-18 8:11 ` Dave Chinner
2013-01-18 19:10 ` Glauber Costa
2013-01-18 19:10 ` Glauber Costa
2013-01-18 19:10 ` Glauber Costa
2013-01-19 0:10 ` Dave Chinner
2013-01-19 0:10 ` Dave Chinner
2013-01-19 0:13 ` Glauber Costa
2013-01-19 0:13 ` Glauber Costa
2013-01-19 0:13 ` Glauber Costa
2013-01-18 0:51 ` Glauber Costa
2013-01-18 0:51 ` Glauber Costa
2013-01-18 0:51 ` Glauber Costa
2013-01-18 8:08 ` Dave Chinner
2013-01-18 8:08 ` Dave Chinner
2013-01-18 19:01 ` Glauber Costa
2013-01-18 19:01 ` Glauber Costa
2013-01-18 19:01 ` Glauber Costa
2012-11-27 23:14 ` [PATCH 10/19] shrinker: add node awareness Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 11/19] fs: convert inode and dentry shrinking to be node aware Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 12/19] xfs: convert buftarg LRU to generic code Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 13/19] xfs: Node aware direct inode reclaim Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 14/19] xfs: use generic AG walk for background " Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 15/19] xfs: convert dquot cache lru to list_lru Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-28 16:17 ` Christoph Hellwig
2012-11-28 16:17 ` Christoph Hellwig
2012-11-28 16:17 ` Christoph Hellwig
2012-11-27 23:14 ` [PATCH 16/19] fs: convert fs shrinkers to new scan/count API Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 17/19] drivers: convert shrinkers to new count/scan API Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-28 1:13 ` Chris Wilson [this message]
2012-11-28 1:13 ` Chris Wilson
2012-11-28 1:13 ` Chris Wilson
2012-11-28 3:17 ` Dave Chinner
2012-11-28 3:17 ` Dave Chinner
2012-11-28 3:17 ` Dave Chinner
2012-11-28 8:21 ` Glauber Costa
2012-11-28 8:21 ` Glauber Costa
2012-11-28 8:21 ` Glauber Costa
2012-11-28 8:21 ` Glauber Costa
2012-11-28 21:28 ` Dave Chinner
2012-11-28 21:28 ` Dave Chinner
2012-11-28 21:28 ` Dave Chinner
2012-11-29 10:29 ` Glauber Costa
2012-11-29 10:29 ` Glauber Costa
2012-11-29 10:29 ` Glauber Costa
2012-11-29 10:29 ` Glauber Costa
2012-11-29 22:02 ` Dave Chinner
2012-11-29 22:02 ` Dave Chinner
2012-11-29 22:02 ` Dave Chinner
2013-06-07 13:37 ` Konrad Rzeszutek Wilk
2013-06-07 13:37 ` Konrad Rzeszutek Wilk
2013-06-07 13:37 ` Konrad Rzeszutek Wilk
2012-11-27 23:14 ` [PATCH 18/19] shrinker: convert remaining shrinkers to " Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` [PATCH 19/19] shrinker: Kill old ->shrink API Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-27 23:14 ` Dave Chinner
2012-11-29 19:02 ` [RFC, PATCH 00/19] Numa aware LRU lists and shrinkers Andi Kleen
2012-11-29 19:02 ` Andi Kleen
2012-11-29 19:02 ` Andi Kleen
2012-11-29 22:09 ` Dave Chinner
2012-11-29 22:09 ` Dave Chinner
2012-11-29 22:09 ` Dave Chinner
2012-12-20 11:45 ` Glauber Costa
2012-12-20 11:45 ` Glauber Costa
2012-12-20 11:45 ` Glauber Costa
2012-12-21 2:50 ` Dave Chinner
2012-12-21 2:50 ` Dave Chinner
2012-12-21 10:41 ` Glauber Costa
2012-12-21 10:41 ` Glauber Costa
2012-12-21 10:41 ` Glauber Costa
2013-01-21 16:08 ` Glauber Costa
2013-01-21 16:08 ` Glauber Costa
2013-01-21 16:08 ` Glauber Costa
2013-01-21 23:21 ` Dave Chinner
2013-01-21 23:21 ` Dave Chinner
2013-01-21 23:21 ` Dave Chinner
2013-01-23 14:36 ` Glauber Costa
2013-01-23 14:36 ` Glauber Costa
2013-01-23 14:36 ` Glauber Costa
2013-01-23 23:46 ` Dave Chinner
2013-01-23 23:46 ` Dave Chinner
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