> -----Original Message----- > From: Jeff Layton [mailto:jlayton@xxxxxxxxxx] > Sent: Monday, December 05, 2011 12:11 PM > To: Jeff Layton > Cc: Myklebust, Trond; linux-nfs@xxxxxxxxxxxxxxx; khoa@xxxxxxxxxx > Subject: Re: [PATCH] nfs: only do COMMIT for range written with direct I/O > > On Wed, 30 Nov 2011 09:07:54 -0500 > Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > When given a range to write with unstable writes, the current code > > always does a COMMIT of the entire file afterward. This is potentially > > expensive on some servers and unnecessary. Instead, just do a COMMIT > > for the offset and count that was written. > > > > Khoa, who reported this bug, stated that this made a big difference in > > performance in their environment, which I believe involves GPFS on the > > server. He didn't pass along any hard numbers so I can't quantify the > > gain, but it stands to reason that clustered filesystems might suffer > > more contention issues when issuing a commit over the whole file. > > > > Reported-by: Khoa Huynh <khoa@xxxxxxxxxx> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > Khoa found that he made a mistake when testing this originally, and any > benefit that the patch provides seems to be negligible. I still think it's safe > and reasonable to only issue a commit for the range that was written, but > there doesn't seem to be any compelling need for this patch right now. > > Trond, do you have an opinion here? Should we go ahead and commit this > patch or something like it, or leave well-enough alone? I'd prefer to wait until I see a tangible benefit. I know that recent kernels do have support for a COMMIT range on the Linux kernel server side, so maybe it is just a question of shooting up an ext4 or XFS based server and running a few tests with a large O_DIRECT writer on one client, and a smaller O_DIRECT writer on another... 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
