From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 3/3] ARM: Add barriers to the I/O accessorsifARM_DMA_MEM_BUFFERABLE
Date: Fri, 9 Jul 2010 15:34:52 +0100 [thread overview]
Message-ID: <20100709143452.GJ22845@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1278685283.11895.52.camel@e102109-lin.cambridge.arm.com>
On Fri, Jul 09, 2010 at 03:21:23PM +0100, Catalin Marinas wrote:
> The patch below changes the __raw_* accessors to inline functions. Do
> you see any problem with this? This would be needed even without the I/O
> ordering patches.
I'd suggest you try building a kernel before and after this patch and
compare the sizes - and then look at the disassembly associated with
these accessors.
Certainly previous gcc versions generated useless instruction overhead
when these were inline functions - partly down to it wanting to make
sure things passed to/from __raw_writeb() and __raw_readb() were
absolutely definitely only 8-bit in size, and partly because this
seems to destroy GCC's ability to spot commonalities between multiple
accesses.
That's the reason why I've never pushed a patch which causes read[bwl]
and write[bwl] to check their arguments a little more strictly - I
found that it caused gcc to generate worse code for these accessors.
next prev parent reply other threads:[~2010-07-09 14:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-09 11:07 [PATCH v2 0/3] Ordered I/O accessors Catalin Marinas
2010-07-09 11:08 ` [PATCH v2 1/3] ARM: Introduce *_relaxed() " Catalin Marinas
2010-07-09 16:08 ` Arnd Bergmann
2010-07-09 16:53 ` Catalin Marinas
2010-07-09 17:17 ` Arnd Bergmann
2010-07-09 18:24 ` Russell King - ARM Linux
2010-07-09 19:30 ` Arnd Bergmann
2010-07-09 22:31 ` Catalin Marinas
2010-07-12 11:39 ` Arnd Bergmann
2010-07-12 11:50 ` Jamie Lokier
2010-07-12 11:53 ` Catalin Marinas
2010-07-12 12:46 ` Jamie Lokier
2010-07-13 15:21 ` Catalin Marinas
2010-07-12 12:00 ` Catalin Marinas
2010-07-09 11:08 ` [PATCH v2 2/3] ARM: Convert L2x0 to use the IO relaxed operations for cache sync Catalin Marinas
2010-07-09 11:08 ` [PATCH v2 3/3] ARM: Add barriers to the I/O accessors if ARM_DMA_MEM_BUFFERABLE Catalin Marinas
2010-07-09 11:41 ` Catalin Marinas
2010-07-09 12:16 ` Russell King - ARM Linux
2010-07-09 13:02 ` [PATCH v2 3/3] ARM: Add barriers to the I/O accessors ifARM_DMA_MEM_BUFFERABLE Catalin Marinas
2010-07-09 14:21 ` [PATCH v2 3/3] ARM: Add barriers to the I/O accessorsifARM_DMA_MEM_BUFFERABLE Catalin Marinas
2010-07-09 14:34 ` Russell King - ARM Linux [this message]
2010-07-09 15:02 ` [PATCH v2 3/3] ARM: Add barriers to the I/OaccessorsifARM_DMA_MEM_BUFFERABLE Catalin Marinas
2010-07-09 11:29 ` [PATCH v2 0/3] Ordered I/O accessors Russell King - ARM Linux
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