From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: vapier.adi@gmail.com
Cc: fujita.tomonori@lab.ntt.co.jp, npiggin@suse.de,
marc@tensilica.com, dmitry.torokhov@gmail.com, jw@emlix.com,
cl@linux.com, penberg@cs.helsinki.fi, mpm@selenic.com,
akpm@linux-foundation.org, os@emlix.com,
Michael.Hennerich@analog.com, linux-input@vger.kernel.org,
linux-kernel@vger.kernel.org, dg@emlix.com, osw@emlix.com,
rientjes@google.com, dbrownell@users.sourceforge.net,
grant.likely@secretlab.ca, chris@zankel.net,
Piet.Delaney@tensilica.com
Subject: Re: [LKML] Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
Date: Wed, 12 May 2010 14:28:51 +0900 [thread overview]
Message-ID: <20100512142904Z.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <AANLkTine8JmtsUo3_z6Cwdgm3LINCkJ9jL21r9eQWRm8@mail.gmail.com>
On Wed, 12 May 2010 00:35:45 -0400
Mike Frysinger <vapier.adi@gmail.com> wrote:
> On Tue, May 11, 2010 at 23:23, FUJITA Tomonori wrote:
> > Seems that kmalloc is not cacheline aligned on some architectures but
> > they works. Probably, we might be just lucky because in general they
> > allocate larger buffers than 64 for DMA via kmalloc and the buffers
> > are aligned on the size?
>
> i think the magic combo is:
> - DMA buffer is written to (receive)
> - some driver state is in the same cacheline as the DMA buffer
> - that driver state is used after the flush but before the DMA finishes
> - only on arches that need software cache coherency
>
> so i could see this not being an obvious issue for many people
Yeah, we don't hit such condition everyday. And as I said, SCSI
usually uses kmalloc'ed buffers rather than the cache size (buffers
are aligned on roundup_pow_of_two(the allocated size)). But I think
that we want to fix this issue explicitly. I guess that it would be
better to start a new thread about this issue.
WARNING: multiple messages have this Message-ID (diff)
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: vapier.adi@gmail.com
Cc: fujita.tomonori@lab.ntt.co.jp, npiggin@suse.de,
marc@tensilica.com, dmitry.torokhov@gmail.com, jw@emlix.com,
cl@linux.com, penberg@cs.helsinki.fi, mpm@selenic.com,
akpm@linux-foundation.org, os@emlix.com,
Michael.Hennerich@analog.com, linux-input@vger.kernel.org,
linux-kernel@vger.kernel.org, dg@emlix.com, osw@emlix.com,
rientjes@google.com, dbrownell@users.sourceforge.net,
grant.likely@secretlab.ca, chris@zankel.net,
Piet.Delaney@tensilica.com
Subject: Re: [LKML] Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
Date: Wed, 12 May 2010 14:28:51 +0900 [thread overview]
Message-ID: <20100512142904Z.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <AANLkTine8JmtsUo3_z6Cwdgm3LINCkJ9jL21r9eQWRm8@mail.gmail.com>
On Wed, 12 May 2010 00:35:45 -0400
Mike Frysinger <vapier.adi@gmail.com> wrote:
> On Tue, May 11, 2010 at 23:23, FUJITA Tomonori wrote:
> > Seems that kmalloc is not cacheline aligned on some architectures but
> > they works. Probably, we might be just lucky because in general they
> > allocate larger buffers than 64 for DMA via kmalloc and the buffers
> > are aligned on the size?
>
> i think the magic combo is:
> - DMA buffer is written to (receive)
> - some driver state is in the same cacheline as the DMA buffer
> - that driver state is used after the flush but before the DMA finishes
> - only on arches that need software cache coherency
>
> so i could see this not being an obvious issue for many people
Yeah, we don't hit such condition everyday. And as I said, SCSI
usually uses kmalloc'ed buffers rather than the cache size (buffers
are aligned on roundup_pow_of_two(the allocated size)). But I think
that we want to fix this issue explicitly. I guess that it would be
better to start a new thread about this issue.
next prev parent reply other threads:[~2010-05-12 5:34 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-06 10:37 [PATCH] ad7877: fix spi word size to 16 bit Oskar Schirmer
2010-05-06 10:37 ` Oskar Schirmer
2010-05-06 10:37 ` [PATCH] ad7877: keep dma rx buffers in seperate cache lines Oskar Schirmer
2010-05-06 18:46 ` Mike Frysinger
2010-05-06 18:46 ` Mike Frysinger
2010-05-07 10:15 ` Oskar Schirmer
2010-05-07 10:15 ` Oskar Schirmer
2010-05-07 18:28 ` Mike Frysinger
2010-05-07 18:28 ` Mike Frysinger
2010-05-08 22:32 ` Johannes Weiner
2010-05-08 22:32 ` Johannes Weiner
2010-05-09 4:45 ` Mike Frysinger
2010-05-09 4:45 ` Mike Frysinger
2010-05-09 8:50 ` Oskar Schirmer
2010-05-09 8:50 ` Oskar Schirmer
2010-05-07 12:07 ` Johannes Weiner
2010-05-10 10:34 ` [PATCH v2] " Oskar Schirmer
2010-05-10 10:34 ` Oskar Schirmer
2010-05-10 10:42 ` [PATCH v3] " Oskar Schirmer
2010-05-10 10:42 ` Oskar Schirmer
2010-05-10 16:39 ` Mike Frysinger
2010-05-10 20:54 ` Dmitry Torokhov
2010-05-10 21:22 ` Andrew Morton
2010-05-10 21:27 ` Mike Frysinger
2010-05-11 6:05 ` Dmitry Torokhov
2010-05-11 6:05 ` Dmitry Torokhov
2010-05-11 6:11 ` Mike Frysinger
2010-05-11 6:11 ` Mike Frysinger
2010-05-11 3:20 ` Andrew Morton
2010-05-11 6:21 ` Dmitry Torokhov
2010-05-11 6:23 ` Mike Frysinger
2010-05-11 6:23 ` Mike Frysinger
2010-05-11 6:33 ` Dmitry Torokhov
2010-05-11 6:33 ` Dmitry Torokhov
2010-05-11 6:37 ` Mike Frysinger
2010-05-11 6:42 ` Pekka Enberg
2010-05-11 13:57 ` Christoph Lameter
2010-05-11 16:52 ` Dmitry Torokhov
2010-05-11 17:31 ` Mike Frysinger
2010-05-11 18:59 ` Pekka Enberg
2010-05-11 20:03 ` Mike Frysinger
2010-05-11 20:07 ` Matt Mackall
2010-05-11 20:10 ` Mike Frysinger
2010-05-11 20:10 ` Mike Frysinger
2010-05-11 20:21 ` Christoph Lameter
2010-05-11 20:34 ` Mike Frysinger
2010-05-11 20:38 ` Pekka Enberg
2010-05-11 20:43 ` Mike Frysinger
2010-05-11 20:43 ` Mike Frysinger
2010-05-11 20:47 ` Pekka Enberg
2010-05-13 6:21 ` Paul Mundt
2010-05-11 20:46 ` Christoph Lameter
2010-05-11 20:54 ` Mike Frysinger
2010-05-11 20:54 ` Mike Frysinger
2010-05-11 21:01 ` Pekka Enberg
2010-05-11 21:11 ` Mike Frysinger
2010-05-11 21:11 ` Mike Frysinger
2010-05-12 1:58 ` FUJITA Tomonori
[not found] ` <20100511214836.GH1726@emlix.com>
2010-05-11 21:53 ` Dmitry Torokhov
2010-05-11 22:39 ` Mike Frysinger
2010-05-11 22:39 ` Mike Frysinger
2010-05-12 2:07 ` [LKML] " Marc Gauthier
2010-05-12 3:03 ` Nick Piggin
2010-05-12 3:23 ` FUJITA Tomonori
2010-05-12 4:35 ` Mike Frysinger
2010-05-12 4:35 ` Mike Frysinger
2010-05-12 5:28 ` FUJITA Tomonori [this message]
2010-05-12 5:28 ` FUJITA Tomonori
2010-05-12 14:37 ` Mike Frysinger
2010-05-12 14:37 ` Mike Frysinger
2010-05-12 18:11 ` Dmitry Torokhov
2010-05-12 18:28 ` Mike Frysinger
2010-05-12 18:28 ` Mike Frysinger
2010-05-12 10:36 ` Johannes Weiner
2010-05-12 12:35 ` Marc Gauthier
2010-05-12 14:36 ` Mike Frysinger
2010-05-12 14:36 ` Mike Frysinger
2010-05-19 12:48 ` David Woodhouse
2010-05-19 13:07 ` Nick Piggin
2010-05-19 13:17 ` David Woodhouse
2010-05-19 13:36 ` Nick Piggin
2010-05-19 13:44 ` Johannes Weiner
2010-05-19 13:52 ` Nick Piggin
2010-05-19 14:38 ` FUJITA Tomonori
2010-05-19 14:58 ` David Woodhouse
2010-05-20 4:42 ` FUJITA Tomonori
2010-05-19 16:37 ` Dmitry Torokhov
2010-05-19 15:00 ` Johannes Weiner
2010-05-17 6:12 ` Michal Simek
2010-05-19 13:00 ` David Woodhouse
2010-05-11 22:37 ` Alan Cox
2010-05-11 20:22 ` Pekka Enberg
2010-05-11 14:12 ` Oskar Schirmer
2010-05-11 14:12 ` Oskar Schirmer
2010-05-06 11:18 ` [PATCH] ad7877: fix spi word size to 16 bit Hennerich, Michael
2010-05-06 11:18 ` Hennerich, Michael
2010-05-06 18:26 ` Mike Frysinger
2010-05-06 18:26 ` Mike Frysinger
2010-05-07 9:41 ` Daniel Glöckner
2010-05-07 9:41 ` Daniel Glöckner
2010-05-07 18:23 ` Mike Frysinger
2010-05-07 18:23 ` Mike Frysinger
2010-05-13 7:53 ` Dmitry Torokhov
2010-05-13 7:53 ` Dmitry Torokhov
2010-05-15 18:15 ` Oskar Schirmer
2010-05-15 18:15 ` Oskar Schirmer
2010-05-16 19:25 ` Mike Frysinger
2010-05-16 19:25 ` Mike Frysinger
2010-05-17 7:29 ` Oskar Schirmer
2010-05-17 7:29 ` Oskar Schirmer
2010-05-17 8:14 ` Hennerich, Michael
2010-05-17 8:14 ` Hennerich, Michael
2010-05-17 8:41 ` Oskar Schirmer
2010-05-17 8:41 ` Oskar Schirmer
2010-05-17 23:49 ` Mike Frysinger
2010-05-17 23:49 ` Mike Frysinger
2010-05-18 0:18 ` H Hartley Sweeten
2010-05-18 0:18 ` H Hartley Sweeten
2010-05-18 8:32 ` Oskar Schirmer
2010-05-18 8:32 ` Oskar Schirmer
2010-05-18 9:37 ` Daniel Glöckner
2010-05-18 9:37 ` Daniel Glöckner
2010-05-18 8:34 ` [PATCH v2] " Oskar Schirmer
2010-05-18 8:34 ` Oskar Schirmer
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