Re: O_DIRECT question

[Linus Torvalds]

On Thu, 11 Jan 2007, Roy Huang wrote:
>
> On a embedded systerm, limiting page cache can relieve memory
> fragmentation. There is a patch against 2.6.19, which limit every
> opened file page cache and total pagecache. When the limit reach, it
> will release the page cache overrun the limit.

I do think that something like this is probably a good idea, even on 
non-embedded setups. We historically couldn't do this, because mapped 
pages were too damn hard to remove, but that's obviously not much of a 
problem any more.

However, the page-cache limit should NOT be some compile-time constant. It 
should work the same way the "dirty page" limit works, and probably just 
default to "feel free to use 90% of memory for page cache".

		Linus
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