https://bugzilla.kernel.org/show_bug.cgi?id=107301 Andreas Dilger <adilger.kernelbugzilla@xxxxxxxxx> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |adilger.kernelbugzilla@dilg | |er.ca --- Comment #12 from Andreas Dilger <adilger.kernelbugzilla@xxxxxxxxx> --- Created attachment 192551 --> https://bugzilla.kernel.org/attachment.cgi?id=192551&action=edit add "no_mbcache We have a patch for Lustre ldiskfs (ext4 modified with Lustre patches) to disable mbcache, since it has similar performance impact for Lustre servers, and provides no value because the xattrs Lustre stores on each file are unique and cannot be shared. Canonical patch location: http://git.hpdd.intel.com/fs/lustre-release.git/blob_plain/HEAD:/ldiskfs/kernel_patches/patches/rhel7/ext4-disable-mb-cache.patch While the referenced patch is for RHEL 7, it is small enough to port easily to the upstream kernel. This patch adds a "no_mbcache" mount option, which Lustre automatically adds to the filesystem options when the servers are mounted. There was a patch to improve mbcache performance in ext4 by making the cache per-sb, but that doesn't improve the contention within a filesystem, and doesn't avoid the fact that mbcache provides absolutely no value for Lustre (or Ceph, it seems). Doing no work at all is better than doing it somewhat more efficiently. The only way I could see this working automatically is if mbcache disabled itself after having a low/zero cache hit ratio within a certain number of inserts, and if not finding any shared xattr blocks when reading from disk. In the meantime, I think having a mount option is a viable alternative for those people who know better than the auto-detection heuristics. -- You are receiving this mail because: You are watching the assignee of the bug. -- 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
