|To:||Michael Sundius <firstname.lastname@example.org>|
|Subject:||Re: memcpy and prefetch|
|From:||David Daney <email@example.com>|
|Date:||Tue, 27 Jan 2009 15:07:45 -0800|
|Cc:||firstname.lastname@example.org, "VomLehn, David" <email@example.com>, firstname.lastname@example.org|
|User-agent:||Thunderbird 220.127.116.11 (X11/20090105)|
Michael Sundius wrote:
I know this topic has been written about but so excuse me if I am redundant. I saw lots of talk in the archives but I don't know if a solution was ever arrivedat. so: what is the current state of the use of prefetch in memcpy()? it seems that it is #undef-ed if CONFIG_DMA_COHERENT is not turned on. is this still because the memcpy does not check to prevent a prefetch of addresses beyond the end of the buffer? If so, what was the reason a solution was abandoned.... also has anyone out there written a memcopy that does use prefetch intelligently (for mips32 that is)?
The Cavium OCTEON port overrides the default memcpy and does use prefetch. It was recently merged (2.6.29-rc2). Look at octeon-memcpy.S
I have thought that memcpy could be generated by mm/page.c as copy_page and clear_page are.
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