On Thu, Jan 06, 2011 at 09:50:39AM +1100, Dave Chinner wrote: > If we want optimised, only-trim-what-we-free behaviour, we need to > hook into the transaction subsystem and issue TRIM commands at the > time extents are actually freed. That is much more complex to > implement but much easier to optimise because it doesn't require > persistent state on disk. However, most devices are simply not ready > to handle the flood of TRIM commands this generates, with > performance degrading by ~10-20% for the best of devices and > _10-100x_ for the worst... I tested a few devices that have zero to 1% degradation, but those were arrays, which allow for queued WRITE SAME/UNMAP commands instead of the unqueued TRIM in ATA. But I'm gettig close to finishing the online discard and will start another benchmark session soon. With PCI-E flash devices that aren't limited by the ATA protocol, and the proposed queueable TRIM command this looks like what we need for the future. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
