On Fri, Oct 12, 2007 at 12:36:01PM +0100, Andrew Clayton wrote: > On Fri, 12 Oct 2007 10:26:13 +1000, David Chinner wrote: > > > You can breath again. Here's a test patch (warning - may harm > > heh > > > kittens - not fully tested or verified) that solves both > > the use-after-free issue (by avoiding it altogether) as well the > > unlink/create latency because the log force is no longer there. > > > > (yay! xfsqa test 016 passes again ;) > > > > It does have other possible side effects triggering extra > > log forces elsewhere on inode writeback and affects sync behaviour > > so it's only a proof of concept at this point. > > What kernel is that against?. I got rejects with 2.6.23 The xfs-dev tree - i.e. the XFS that will be in 2.6.25 ;) > However I tried a 2.6.18 on the file server and ran my test, it didn't > show the problem. I then made a 2.6.23 but with the patch from my git > bisect reverted. > > Doing the test with that kernel, while writing a 1GB file I saw only > one > 1 second latency (1.2) and only a few ~ 0.5 second latencies. > > However over the longer term I'm still seeing latencies > 1 second. Sure - you've got a busy disk. If the truncate has to flush the log and wait for space, then it's going to take some time for I/Os to complete. Full queue + busy disk == unpredictable latency for all operations. > Just leaving my strace test running (no dd) on the raid filesystem I see > the > latencies come when the raid5 stripe cache fills up. So I think I'm > perhaps seeing another problem here. Software raid isn't good for latency, either ;) Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
