On 2012-01-25, at 7:00 AM, Jan Kara wrote: > On Wed 25-01-12 14:35:52, Wu Fengguang wrote: >> On Tue, Jan 24, 2012 at 11:15:13PM -0700, Andreas Dilger wrote: >>> I'm all in favour of 1MB (aligned) readahead. >> >> 1MB readahead aligned to i*1MB boundaries? I like this idea. It will >> work well if the filesystems employ the same alignment rule for large >> files. > > Yeah. Clever filesystems (e.g. XFS) can be configured to align files e.g. > to raid stripes AFAIK so for them this could be worthwhile. Ext4 will also align IO to 1MB boundaries (from the start of LUN/partition) by default. If the mke2fs code detects the underlying RAID geometry (or the sysadmin sets this manually with tune2fs) it will store this in the superblock for the allocator to pick a better alignment. Cheers, Andreas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
