On Tue, 2008-04-15 at 06:39 -0700, Martin Knoblauch wrote: > Hi, > > while tracking down a very interesting interaction between Sun/SAM-FS and Linux NFS clients, we found out that the value of NFS_MAX_READ_AHEAD is to agressive/big for the specific use-case. > > For testing, instead of always recompiling the kernel with different values, I came up with the following patch. It introduces a tunable "/proc/sys/fs/nfs/nfs_ra_factor" with possible values between 0-15. > > Not sure whether it is actually a good thing to have. Better would be to set the read-ahead factor per filesystem via a mount option. > > The patch is against 2.6.24. It applies with offsets against 2.6.25-rc9. In case my mail client messes up the whitespace, the patch is also attached. NFS_MAX_READ_AHEAD just sets an upper limit on the standard vfs/mm-level page readahead algorithm. If you need finer control over that readahead algorithm, then the kernel already has full support for the posix_fadvise() system call. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
