Re: cache limit

[Andrew Morton]

Erik Andersen <andersen@xxxxxxxxxxxx> wrote:
>
> On Mon Aug 18, 2003 at 11:20:24PM -0700, Andrew Morton wrote:
> > Denis Vlasenko <vda@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > There was a discussion (and patches) in the middle of 2.5 series
> > >  about O_STREAMING open flag which mean "do not aggressively cache
> > >  this file". Targeted at MP3/video playing, copying large files and such.
> > > 
> > >  I don't know whether it actually was merged. If it was,
> > >  your program can use it.
> > 
> > It was not.  Instead we have fadvise.  So it would be appropriate to change
> > applications such as rsync to optionally run
> > 
> > 	posix_fadvise(fd, 0, -1, POSIX_FADV_DONTNEED)
> > 
> > against file descriptors just before closing them, so all the pagecache
> > gets thrown away.  (Well, most of the pagecache - dirty pages won't get
> > dropped - the app must fsync the files by hand first if it wants this)
> 
> This is not supported in 2.4.x though, right?

No, it is not.

> What if I don't want to fill up the pagecache with garbage in the
> first place?

Call fadvise(POSIX_FADV_DONTNEED) more frequently or use O_DIRECT.

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