----- Original Message ----- > From: "Poornima Gurusiddaiah" <[email protected]> > To: "Dan Lambright" <[email protected]>, "Nithya Balachandran" > <[email protected]> > Cc: "Gluster Devel" <[email protected]> > Sent: Tuesday, August 23, 2016 12:56:38 AM > Subject: md-cache changes and impact on tiering > > Hi, > > The basic patches for md-cache and integrating it with cache-invalidation is > merged in master. You could try master build and enable the following > settings, to see if there is any impact on tiering performance at all: > > # gluster volume set <volname> performance.stat-prefetch on > # gluster volume set <volname> features.cache-invalidation on > # gluster volume set <volname> performance.cache-samba-metadata on > # gluster volume set <volname> performance.md-cache-timeout 600 > # gluster volume set <volname> features.cache-invalidation-timeout 600
On the tests I run, this cut the number of LOOKUPs by about three orders of magnitude. Each saved lookup reduces a round trip over the network. I'm running a "small file" performance test. It creates 16K 64 byte files in a seven level directory. It then reads each file twice. Configuration is HOT: 2 x 2 ramdisk COLD: 2 x (8 + 4) disk, network is 10000Mb/s 9000 mtu. The number of lookups is a factor of the number of directories and subvolumes. On each I/O the file is re-opened and each directory is laboriously rechecked for existence/permission. Without using md-cache, these lookups used to be further propagated across each subvolume by DHT to obtain the entire layout. So it would be something like order of 16K*7*26 round trips across the network. The counts are all visible with gluster profile. > > Note: It has to be executed in the same order. > > Tracker bug: https://bugzilla.redhat.com/show_bug.cgi?id=1211863 > Patches: > http://review.gluster.org/#/q/status:open+project:glusterfs+branch:master+topic:bug-1211863 > > Thanks, > Poornima > _______________________________________________ Gluster-devel mailing list [email protected] http://www.gluster.org/mailman/listinfo/gluster-devel
