On Sun, 2006-03-19 at 21:24 -0500, Theodore Ts'o wrote: > On Sun, Mar 19, 2006 at 10:59:26AM +0100, Arjan van de Ven wrote: > > > > > In general, I doubt directory readahead actually buys you *that* much, > > > because most workloads follow up the readdir with a stat() or an > > > open() call for each file returned, or something which requires > > > reading in the inode. In addition, it's rare that the directory will > > > be contiguously allocated, which also cuts down on the value of the > > > readahead. > > > > what it buys you shows up on raid1 I suppose... while disk 0 is doing > > the head seek for the stat/open, disk1 is doing the head seek for the > > next directory entry.... so I can see that being a big gain in that > > specific circumstance. > > > > As long as you have the spare disk bandwifth and disk1 isn't needed > reading the directory entry for some other make process as part of the > "make -j16" kernel build... sure.... on the flipside.. if the readahead request is in the elevator it may be merged with that make ;) so I agree, it's not even a guaranteed win on raid1 _______________________________________________ Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
