On Mittwoch, 1. September 2010 Dave Chinner wrote: > You're probably getting RMW cycles on inode writeback. I've been > noticing this lately with my benchmarking - the VM is being _very > aggressive_ reclaiming page cache pages vs inode caches and as a > result the inode buffers used for IO are being reclaimed between the > time it takes to create the inodes and when they are written back. > Hence you get lots of reads occurring during inode writeback. > > By issuing a sync, you clear out all the inode writeback and all the > RMW cycles go away. As a result, there is more disk throughput > availble for the unlink processes. There is a good chance this is > the case as the number of reads after the sync drop by an order of > magnitude... Nice explanation. > > Now it can be that the sync just causes more writes and stalls > > reads so overall it's slower, but I'm wondering why none of the > > devices says "100% util", which should be the case on deletes? Or > > is this again the "mistake" of the utilization calculation that > > writes do not really show up there? > > You're probably CPU bound, not IO bound. This is a hexa-core AMD Phenom(tm) II X6 1090T Processor with up to 3.2GHz per core, so that shouldn't be - or is there only one core used? I think I read somewhere that each AG should get a core or so... Thanks for your explanation. -- mit freundlichen Grüssen, Michael Monnerie, Ing. BSc it-management Internet Services http://proteger.at [gesprochen: Prot-e-schee] Tel: 0660 / 415 65 31 ****** Aktuelles Radiointerview! ****** http://www.it-podcast.at/aktuelle-sendung.html // Wir haben im Moment zwei Häuser zu verkaufen: // http://zmi.at/langegg/ // http://zmi.at/haus2009/
Attachment:
signature.asc
Description: This is a digitally signed message part.
_______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
