Re: [PATCH] Add memcpy_cachebypass, a copy routine that tries to keep cache pressure down

[Arjan van de Ven <arjan@infradead.org>]

On Tue, 2006-07-11 at 13:50 -0700, Bryan O'Sullivan wrote:
> This copy routine is memcpy-compatible, but on some architectures will use
> cache-bypassing loads to avoid bringing the source data into the cache.
> 
> One case where this is useful is when a device issues a DMA to a memory
> region, and the CPU must copy the DMAed data elsewhere before doing any
> work with it.  Since the source data is read-once, write-never from the
> CPU's perspective, caching those addresses can only evict potentially
> useful data.
> 
> We provide an x86_64 implementation that uses SSE non-temporal loads,
> and a generic version that falls back to plain memcpy.
> 
> Implementors for other arches should not use cache-bypassing stores to
> the destination, as in most cases, the destination is accessed almost
> immediately after a copy finishes.
> 
> Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
> Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>


Acked-by: Arjan van de Ven <arjan@Linux.intel.com>


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