Re: [PATCH] O_STREAMING - flag for optimal streaming I/O

From: Mike Fedyk (
Date: Thu Oct 10 2002 - 17:50:50 EST

On Thu, Oct 10, 2002 at 03:39:19PM +0200, Giuliano Pochini wrote:
> > Look, the pagecache is already smart. New stuff will replace unusued
> > old stuff. On VM pressure, the pagecache will be pruned. Streaming I/O
> > is a fundamentally different problem in that the data is so large it
> > _continually_ thrashes the pagecache. Such I/O is sequential and
> > use-once. You end up with a permanent waste of memory (the cached
> > I/O).
> When a process opens a file with O_STREAMING, it tells the kernel
> it will use the data only once, but it tells nothing about other
> tasks. If that process reads something which is already cached,
> then it must not drop it because someone other used it recently
> and IMHO pagecache only should be allowed to drop it.

You are missing the point. If the app thinks that might happen, it
shouldn't use O_STREAMING.

Though, how do you get around some binary app using O_STREAMING when it
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