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From: Ben Widawsky <ben@bwidawsk.net>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 17/18] drm/i915: Use a slab for object allocation
Date: Wed, 7 Nov 2012 13:59:31 +0000	[thread overview]
Message-ID: <20121107135931.69055dde@bwidawsk.net> (raw)
In-Reply-To: <eeac1e$4t4n0f@AZSMGA002.ch.intel.com>

On Mon, 05 Nov 2012 20:57:05 +0000
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> On Mon, 5 Nov 2012 17:49:35 +0000, Ben Widawsky <ben@bwidawsk.net> wrote:
> > On Fri, 19 Oct 2012 18:03:23 +0100
> > Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > 
> > > The primary purpose of this was to debug some use-after-free memory
> > > corruption that was causing an OOPS inside drm/i915. As it turned out
> > > the corruption was being caused elsewhere and i915.ko as a major user of
> > > many objects was being hit hardest.
> > > 
> > > Indeed as we do frequent the generic kmalloc caches, dedicating one to
> > > ourselves (or at least naming one for us depending upon the core) aids
> > > debugging our own slab usage.
> > > 
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > > Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> > 
> > So I previously acked this patch, but you dropped that, so now you get
> > more words.
> > 
> > Why not go all the way and move all allocations we do in i915 to this
> > slab (adding a flag with whether or not to zero the memory first)? While
> > I agree in terms of space, nothing takes up as much as objects, I think
> > it would be nice to do this so we can totally track what our driver is
> > doing. In fact I would suggest this is something which core drm should
> > provide to all of the drivers (we already use drm_alloc calls in some
> > places).
> 
> I thought the slab cache was a fixed size, so presumably you mean
> introduce a slab per object we allocate? Of which the only other
> interesting one is the requests. And we don't tend to have many requests
> pending at any one time (outside of exceptional error cases), unlike the
> thousands of bo that tend to be allocated. So is it worth dedicating a
> separate slab to the few but frequently allocated requests?
> -Chris
> 

I guess I wasn't really thinking about the details. I knew in the back
of my mind that the slab cache was a fixed size, but was thinking we
could have a generically large enough object for most of our other
things (I think they're mostly small except for dev_priv). But, now
thinking about it a bit, I guess that wastes the memory we're trying to
scrutinize, so it's probably silly.

In any case, this made me review kmem_cache_create a bit, so we can bump
this patch to:
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

-- 
Ben Widawsky, Intel Open Source Technology Center

  reply	other threads:[~2012-11-07 13:59 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-19 17:03 [PATCH 01/18] drm: Introduce drm_mm_create_block() Chris Wilson
2012-10-19 17:03 ` [PATCH 02/18] drm/i915: Fix detection of stolen base for gen2 Chris Wilson
2012-11-01 23:51   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 03/18] drm/i915: Fix location of stolen memory register for SandyBridge+ Chris Wilson
2012-10-26 21:58   ` Ben Widawsky
2012-10-28  9:48     ` Chris Wilson
2012-10-28 17:52       ` Ben Widawsky
2012-11-02  0:08       ` Ben Widawsky
2012-11-02  8:54         ` Chris Wilson
2012-11-05 13:53           ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 04/18] drm/i915: Avoid clearing preallocated regions from the GTT Chris Wilson
2012-10-26 22:22   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 05/18] drm: Introduce an iterator over holes in the drm_mm range manager Chris Wilson
2012-11-05 13:41   ` Ben Widawsky
2012-11-05 15:13     ` Chris Wilson
2012-10-19 17:03 ` [PATCH 06/18] drm/i915: Delay allocation of stolen space for FBC Chris Wilson
2012-11-05 13:44   ` Ben Widawsky
2012-11-05 15:24     ` Chris Wilson
2012-10-19 17:03 ` [PATCH 07/18] drm/i915: Defer allocation of stolen memory for FBC until actual first use Chris Wilson
2012-11-05 15:00   ` Ben Widawsky
2012-11-05 15:28     ` Chris Wilson
2012-11-05 15:32       ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 08/18] drm/i915: Allow objects to be created with no backing pages, but stolen space Chris Wilson
2012-10-19 17:03 ` [PATCH 09/18] drm/i915: Differentiate between prime and stolen objects Chris Wilson
2012-10-19 17:03 ` [PATCH 10/18] drm/i915: Support readback of stolen objects upon error Chris Wilson
2012-11-05 15:41   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 11/18] drm/i915: Handle stolen objects in pwrite Chris Wilson
2012-10-19 17:03 ` [PATCH 12/18] drm/i915: Handle stolen objects for pread Chris Wilson
2012-10-19 17:03 ` [PATCH 13/18] drm/i915: Introduce i915_gem_object_create_stolen() Chris Wilson
2012-11-05 16:32   ` Ben Widawsky
2012-11-05 16:59     ` Chris Wilson
2012-11-05 17:34       ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 14/18] drm/i915: Allocate fbcon from stolen memory Chris Wilson
2012-10-19 17:03 ` [PATCH 15/18] drm/i915: Allocate ringbuffers " Chris Wilson
2012-10-19 17:03 ` [PATCH 16/18] drm/i915: Allocate overlay registers " Chris Wilson
2012-11-05 17:39   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 17/18] drm/i915: Use a slab for object allocation Chris Wilson
2012-10-24 20:21   ` Paulo Zanoni
2012-11-05 17:49   ` Ben Widawsky
2012-11-05 20:57     ` Chris Wilson
2012-11-07 13:59       ` Ben Widawsky [this message]
2012-11-05 18:07   ` Ben Widawsky
2012-11-05 18:10     ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 18/18] drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl Chris Wilson
2012-10-22 22:21   ` Jesse Barnes
2012-10-23  7:20     ` Daniel Vetter
2012-10-23 17:50       ` Eric Anholt
2012-10-26 21:47 ` [PATCH 01/18] drm: Introduce drm_mm_create_block() Ben Widawsky
2012-10-28  9:57   ` Chris Wilson
2012-10-28 18:12     ` Ben Widawsky
2012-10-28 18:14       ` Ben Widawsky

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