tytso@xxxxxxx wrote: > On Tue, Jul 06, 2010 at 03:15:00PM -0700, Daniel Taylor wrote: ... > > Speaking of fallocate.... if this is a NAS box than the file is > probably written using CIFS, right? Are you using a modern version of > Samba? If you are use a new enough libc (that understands the > fallocate system call) and a new enough version of Samba, the > userspace should be using fallocate() to more efficiently allocate the > space. This is a feature which is not in ext3, but it is supported by > ext4, and it's a major win. The basic idea was discovered a while > ago, and was written up here: > > http://software.intel.com/en-us/articles/windows-client-cifs-behavior-can-slow-linux-nas-performance/ > > (This was a 2007 report, and back then ext4 wasn't ready, so the only > file system available was XFS, which did have both delayed allocation > and fallocate support for preallocation. XFS is a good filesystem, > although it often tends to be a bit memory-hungry for many bookshelf > NAS systems.) XFS is actually a favorite of the ARM embedded NAS space :) > See also see here for a patch (but I'm pretty sure this functionality > is already in the most recent version of Samba if I recall correctly): > > https://bugzilla.redhat.com/show_bug.cgi?id=525532 that patch is rather simplistic, FWIW; at least for XFS it -hurt- perf due to the unwritten->written conversion and the relatively small, frequent preallocations. More smarts to merge up multiple 1-byte-writes into a large preallocation might help, as the bug mentions. But ... is something like it already in samba? that'd be nifty, but I wasn't aware of that. There is a preallocation-sounding switch but I think it doesn't do what you think it does. I'd have to go look up details, though. -Eric > I know a fair number of folks on the Samba core team; most of them > have been hired by companies to work full-time on CIFS support > (usually using Samba), but some of them may still be available to help > out on a consulting basis... let me know if you'd like me to make some > introductions. > > - Ted > > P.S. Amir, this is one of the reason why you folks should seriously think > about merging Next3 support into ext4. :-) -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
