From: msalter@redhat.com (Mark Salter)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/3] RFC: addition to DMA API
Date: Thu, 01 Sep 2011 15:14:18 -0400 [thread overview]
Message-ID: <1314904459.1439.24.camel@deneb.redhat.com> (raw)
In-Reply-To: <20110901173149.GE2803@e102144-lin.cambridge.arm.com>
On Thu, 2011-09-01 at 18:31 +0100, Will Deacon wrote:
> I don't think what we're seeing in this case is caused by mismatched memory
> attributes, especially as passing `nosmp' on the command-line makes the
> performance issue disappear.
I'm coming to think we are dealing with two different problems.
We have the original problem where adding the write buffer flush
to EHCI gives a 4x performance boost to USB. Also adding nosmp to
the cmdline gives pretty much the same boost. This is looking like
something other than just data getting held up in a write buffer.
On the other hand, on a nosmp kernel, I get about 3-4% performance
boost for hdparm -t using the write buffer flush patch vs. without
it.
So, regardless of what turns out to be the actual cause of the 4x
problem, it may still be worthwhile to have the explicit write
buffer sync API if we can't avoid using buffered mappings for DMA.
--Mark
next prev parent reply other threads:[~2011-09-01 19:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-31 21:30 [PATCH 0/3] RFC: addition to DMA API Mark Salter
2011-08-31 21:30 ` [PATCH 1/3] add dma_coherent_write_sync " Mark Salter
2011-09-01 2:59 ` Josh Cartwright
2011-09-01 9:57 ` Michał Mirosław
2011-09-01 12:36 ` Mark Salter
2011-09-06 14:30 ` Catalin Marinas
2011-08-31 21:30 ` [PATCH 2/3] define ARM-specific dma_coherent_write_sync Mark Salter
2011-09-06 14:32 ` Catalin Marinas
2011-09-06 14:37 ` Mark Salter
2011-09-06 14:48 ` Catalin Marinas
2011-09-06 15:02 ` Mark Salter
2011-10-03 1:40 ` Jon Masters
2011-10-03 8:44 ` Catalin Marinas
2011-10-03 9:24 ` Jon Masters
2011-08-31 21:30 ` [PATCH 3/3] add dma_coherent_write_sync calls to USB EHCI driver Mark Salter
2011-09-01 2:33 ` Ming Lei
2011-09-01 2:09 ` [PATCH 0/3] RFC: addition to DMA API Ming Lei
2011-09-01 3:09 ` Alan Stern
2011-09-01 3:41 ` Ming Lei
2011-09-01 8:45 ` Will Deacon
2011-09-01 9:14 ` Ming Lei
2011-09-01 15:42 ` Alan Stern
2011-09-01 16:04 ` Russell King - ARM Linux
2011-09-01 17:31 ` Will Deacon
2011-09-01 18:07 ` Russell King - ARM Linux
2011-09-01 19:14 ` Mark Salter [this message]
2011-09-01 15:22 ` Alan Stern
2011-09-01 15:56 ` Ming Lei
2011-09-01 16:48 ` Alan Stern
2011-09-02 0:59 ` Ming Lei
2011-09-02 13:53 ` Alan Stern
2011-09-01 9:11 ` Will Deacon
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