linux-kernel - Re: [RFC/PATCH 2/2] slub: Don't share struct kmem

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Message-ID: <BANLkTinMC9HTjTKtGeJjG-6Gnz2w4FZvyw@mail.gmail.com>
Date:	Mon, 25 Apr 2011 22:25:36 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	linux-kernel@...r.kernel.org, David Rientjes <rientjes@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC/PATCH 2/2] slub: Don't share struct kmem_cache for shared caches

On Mon, 25 Apr 2011, Pekka Enberg wrote:
>> This patch changes the slab cache sharing in SLUB to only share 'struct
>> kmem_cpu_cache' which contains the actual list of slabs and object freelists.
>> We no longer share 'struct kmem_cache' between merged caches so /proc/slabinfo
>> statistics work as expected:

On Mon, Apr 25, 2011 at 10:09 PM, Christoph Lameter <cl@...ux.com> wrote:
> I am a bit confused. Struct kmem_cache contains per slab
> allocation information and all pages have pointers to struct kmem_cache.
>
> So we have pages now on the kmem_cache_cpu list with varying kmem_cache
> pointers? How do we figure out which cache a page belongs to? It seems
> that a page from one cache can be freed to the freelists of another.

We share the freelist so it goes to the same freelist. However, I
completely forgot about page to struct kmem_cache mapping so stats
won't work properly.

On Mon, Apr 25, 2011 at 10:09 PM, Christoph Lameter <cl@...ux.com> wrote:
> Does this even run right with the debugging enabled?

It boots OK to minimal userspace under KVM with slub_debug. But no, I
didn't test it properly yet.

                        Pekka
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