Re: Swap

[Andrew Morton]

Dan Maas wrote:
> 
> > Uhhhh, read his original mail.  When using mmap() he had
> > problems with the VM doing bad page replacement, while
> > read() was smooth.
> 
> I should add that I did experiment with madvise(MADV_SEQUENTIAL) on the
> mapping, and with madvise(MADV_WILLNEED) on pages about to be needed. These
> had no effect. What *did* help with underruns was pre-touching each page in
> a large block (120KB), before sending that block to the output device. At
> that point I thought the mmap() code was getting to be more complicated that
> it was worth so I just dropped back to read()...

There's a new system call, sys_readahead() which does what you want.

It would be nice to make the pagein code smarter though.

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