On Thu, Jan 07, 2016 at 09:04:54AM +1100, Dave Chinner wrote: > On Wed, Jan 06, 2016 at 10:15:25AM -0500, Mark Seger wrote: > > I've recently found the performance our development swift system is > > degrading over time as the number of objects/files increases. This is a > > relatively small system, each server has 3 400GB disks. The system I'm > > currently looking at has about 70GB tied up in slabs alone, close to 55GB > > in xfs inodes and ili, and about 2GB free. The kernel > > is 3.14.57-1-amd64-hlinux. > > So you go 50M cached inodes in memory, and a relatively old kernel. > > > Here's the way the filesystems are mounted: > > > > /dev/sdb1 on /srv/node/disk0 type xfs > > (rw,noatime,nodiratime,attr2,nobarrier,inode64,logbufs=8,logbsize=256k,sunit=512,swidth=1536,noquota) > > > > I can do about 2000 1K file creates/sec when running 2 minute PUT tests at > > 100 threads. If I repeat that tests for multiple hours, I see the number > > of IOPS steadily decreasing to about 770 and the very next run it drops to > > 260 and continues to fall from there. This happens at about 12M files. > > According to the numbers you've provided: > > lookups creates removes > Fast: 1550 1350 300 > Slow: 1000 900 250 > > This is pretty much what I'd expect on the XFS level when going from > a small empty filesystem to one containing 12M 1k files. > > That does not correlate to your numbers above, so it's not at all > clear that there is realy a problem here at the XFS level. > > > The directory structure is 2 tiered, with 1000 directories per tier so we > > can have about 1M of them, though they don't currently all exist. > > That's insane. > > The xfs directory structure is much, much more space, time, IO and > memory efficient that a directory hierachy like this. The only thing > you need a directory hash hierarchy for is to provide sufficient > concurrency for your operations, which you would probably get with a > single level with one or two subdirs per filesystem AG. BTW, you might want to read the section on directory block size for a quick introduction to XFS directory design and scalability: https://git.kernel.org/cgit/fs/xfs/xfs-documentation.git/tree/admin/XFS_Performance_Tuning/filesystem_tunables.asciidoc Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
