From: Andrew Morton <akpm@linux-foundation.org>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
kamezawa.hiroyu@jp.fujitsu.com, kosaki.motohiro@jp.fujitsu.com,
Joe Perches <joe@perches.com>
Subject: Re: [slubllv7 05/17] mm: Rearrange struct page
Date: Thu, 9 Jun 2011 09:45:26 -0700 [thread overview]
Message-ID: <20110609094526.1571774c.akpm@linux-foundation.org> (raw)
In-Reply-To: <4DF0991E.6060907@cs.helsinki.fi>
On Thu, 09 Jun 2011 12:57:50 +0300 Pekka Enberg <penberg@cs.helsinki.fi> wrote:
> On 6/1/11 8:25 PM, Christoph Lameter wrote:
> > We need to be able to use cmpxchg_double on the freelist and object count
> > field in struct page. Rearrange the fields in struct page according to
> > doubleword entities so that the freelist pointer comes before the counters.
> > Do the rearranging with a future in mind where we use more doubleword
> > atomics to avoid locking of updates to flags/mapping or lru pointers.
> >
> > Create another union to allow access to counters in struct page as a
> > single unsigned long value.
> >
> > The doublewords must be properly aligned for cmpxchg_double to work.
> > Sadly this increases the size of page struct by one word on some architectures.
> > But as a resultpage structs are now cacheline aligned on x86_64.
Is it worth this cost?
> > Signed-off-by: Christoph Lameter<cl@linux.com>
>
> I'd like to queue this SLUB patch series to linux-next through slab.git.
> Any NAKs or ACKs for this patch?
>
> > include/linux/mm_types.h | 89 +++++++++++++++++++++++++++++++----------------
> > 1 file changed, 60 insertions(+), 29 deletions(-)
> >
> > Index: linux-2.6/include/linux/mm_types.h
> > ===================================================================
> > --- linux-2.6.orig/include/linux/mm_types.h 2011-05-31 09:46:41.912987862 -0500
> > +++ linux-2.6/include/linux/mm_types.h 2011-05-31 09:46:44.282987846 -0500
> > @@ -30,52 +30,74 @@ struct address_space;
> > * moment. Note that we have no way to track which tasks are using
> > * a page, though if it is a pagecache page, rmap structures can tell us
> > * who is mapping it.
> > + *
> > + * The objects in struct page are organized in double word blocks in
> > + * order to allows us to use atomic double word operations on portions
> > + * of struct page. That is currently only used by slub but the arrangement
> > + * allows the use of atomic double word operations on the flags/mapping
> > + * and lru list pointers also.
I don't really like the word "word" much. There's always uncertainty
about whether thee and me are talking about the same thing. And
perhaps one day words will be 64-bit.
So if we mean 32-bit, let's say 32-bit?
> > +/*
> > + * If another subsystem starts using the double word pairing for atomic
> > + * operations on struct page then it must change the #if to ensure
> > + * proper alignment of the page struct.
> > + */
> > +#if defined(CONFIG_SLUB)&& defined(CONFIG_CMPXCHG_LOCAL)
> > + __attribute__((__aligned__(2*sizeof(unsigned long))))
> > +#endif
I guess we need a "hey, use __aligned" checkpatch rule.
next prev parent reply other threads:[~2011-06-09 16:44 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-01 17:25 [slubllv7 00/17] SLUB: Lockless freelists for objects V7 Christoph Lameter
2011-06-01 17:25 ` [slubllv7 01/17] slub: Push irq disable into allocate_slab() Christoph Lameter
2011-06-01 17:25 ` [slubllv7 02/17] slub: Do not use frozen page flag but a bit in the page counters Christoph Lameter
2011-06-01 17:25 ` [slubllv7 03/17] slub: Move page->frozen handling near where the page->freelist handling occurs Christoph Lameter
2011-06-01 17:25 ` [slubllv7 04/17] x86: Add support for cmpxchg_double Christoph Lameter
2011-06-09 9:53 ` Pekka Enberg
2011-06-10 15:17 ` Christoph Lameter
2011-06-11 9:50 ` Pekka Enberg
2011-06-11 17:02 ` Christoph Lameter
2011-06-14 5:49 ` Pekka Enberg
2011-06-14 8:04 ` Ingo Molnar
2011-06-14 14:04 ` Christoph Lameter
2011-06-14 15:05 ` H. Peter Anvin
2011-06-15 8:55 ` Tejun Heo
2011-06-15 14:26 ` Christoph Lameter
2011-06-15 16:39 ` Tejun Heo
2011-06-15 17:19 ` Christoph Lameter
2011-06-25 23:49 ` [tip:x86/atomic] " tip-bot for Christoph Lameter
2011-06-01 17:25 ` [slubllv7 05/17] mm: Rearrange struct page Christoph Lameter
2011-06-09 9:57 ` Pekka Enberg
2011-06-09 16:45 ` Andrew Morton [this message]
2011-06-09 17:03 ` [PATCH] checkpatch: Add a "prefer __aligned" check Joe Perches
2011-06-01 17:25 ` [slubllv7 06/17] slub: Add cmpxchg_double_slab() Christoph Lameter
2011-07-11 19:55 ` Eric Dumazet
2011-07-12 15:59 ` Christoph Lameter
2011-07-12 16:06 ` Eric Dumazet
2011-07-12 16:47 ` Christoph Lameter
2011-07-12 18:40 ` H. Peter Anvin
2011-07-12 18:53 ` Christoph Lameter
2011-07-12 20:40 ` H. Peter Anvin
2011-06-01 17:25 ` [slubllv7 07/17] slub: explicit list_lock taking Christoph Lameter
2011-06-01 17:25 ` [slubllv7 08/17] slub: Pass kmem_cache struct to lock and freeze slab Christoph Lameter
2011-06-01 17:25 ` [slubllv7 09/17] slub: Rework allocator fastpaths Christoph Lameter
2011-06-01 17:25 ` [slubllv7 10/17] slub: Invert locking and avoid slab lock Christoph Lameter
2011-06-01 17:25 ` [slubllv7 11/17] slub: Disable interrupts in free_debug processing Christoph Lameter
2011-06-01 17:25 ` [slubllv7 12/17] slub: Avoid disabling interrupts in free slowpath Christoph Lameter
2011-06-01 17:25 ` [slubllv7 13/17] slub: Get rid of the another_slab label Christoph Lameter
2011-06-01 17:25 ` [slubllv7 14/17] slub: Add statistics for the case that the current slab does not match the node Christoph Lameter
2011-06-01 17:25 ` [slubllv7 15/17] slub: fast release on full slab Christoph Lameter
2011-06-01 17:25 ` [slubllv7 16/17] slub: Not necessary to check for empty slab on load_freelist Christoph Lameter
2011-06-01 17:26 ` [slubllv7 17/17] slub: slabinfo update for cmpxchg handling Christoph Lameter
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