On Wed, 11 Sep 2002, Xuan Baldauf wrote:
> Hello,
>
> I wonder wether Linux implements a kind of heuristic
> readahead for filesystems:
>
> If an application reads a directory with getdents() and if
> in the past, it stat()ed a significant part of the directory
> entries, it is likely that it will stat() every entry of
> every directory it reads with getdents() in the future. Thus
> readahead for the stat data could improve the perfomance,
> especially if the stat data is located closely to each other
> on disk.
>
> If an application did a stat()..open()..read() sequence on a
> file, it is likely that, after the next stat(), it will open
> and read the mentioned file. Thus, one could readahead the
> start of a file on stat() of that file.
>
> Combined: If an application walks a directory tree and
> visits each file, it is likely that it will continue up to
> the end of that tree.
M$ Win XP does exactly something like this and keep applications
( windows\prefetch ) and boot profiles that it uses to prefetch disk data
and avoid long page fault latencies. It does kind-of-work but care should
be taken adopting a similar technique on Linux ( patents ).
- Davide
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Sep 15 2002 - 22:00:26 EST