Re: memcpy and prefetch

[David Daney <ddaney@caviumnetworks.com>]

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 arrived
> at. 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.
David Daney