Messages in this thread | | | Date | Mon, 15 Dec 2003 22:39:03 -0800 | From | Andrew Morton <> | Subject | Re: question about max_readahead for ide devices in 2.4? |
| |
John Salmon <jsalmon@thesalmons.org> wrote: > > > > 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?
That's correct - it's all a bit weird. You should use
blockdev --setra 511 /dev/hda
for IDE devices. Not sure about scsi. You may as well set /proc/sys/vm/max-readahead to the same thing. - 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/
| |