lkml.org 
[lkml]   [2003]   [Dec]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subjectquestion about max_readahead for ide devices in 2.4?


Several "tuning" recommendations suggest that sequential accesses of
large files, and hence the performance of busy web servers, can be improved
by changing the maximum readahead value with, e.g.,

echo 511 > /proc/sys/vm/max-readahead
But it looks to me like get_max_readahead in filemap.c ignores the
value set by /proc/sys in favor of max_readahead[major][minor] whenever
max_readahead[major] is non-NULL. And furthermore that
max_readahead[major] IS initialized to non-NULL for ide devices in
init_gendisk. (N.B. I'm looking at 2.4 sources).

Conclusion: echoing a value into /proc/sys/vm/max-readahead won't change the
readahead behavior for already-probed IDE devices.

Is this correct, or am I missing something?

Thanks,
John Salmon
-
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/

\
 
 \ /
  Last update: 2005-03-22 13:59    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site