On Fri, Jan 22, 2016 at 04:43:46PM +0000, Joe Thornber wrote: > On Fri, Jan 22, 2016 at 02:38:28PM +0100, Lars Ellenberg wrote: > > We have seen lvremove of thin snapshots sometimes minutes, > > even ~20 minutes before. > > I did some work on speeding up thin removal in autumn '14, in > particular agressively prefetching metadata pages sped up the tree > traversal hugely. Could you confirm you're seeing pauses of this > duration with currently kernels please? There is https://bugzilla.redhat.com/show_bug.cgi?id=990583 Bug 990583 - lvremove of thin snapshots takes 5 to 20 minutes (single core cpu bound?) >From August 2013, closed by you in October 2015, as "not a bug", also pointing to meta data prefetch. Now, you tell me, how prefetching meta data (doing disk IO more efficiently) helps with something that is clearly CPU bound (eating 100% single core CPU traversing whatever)... Reason I mention this bug again here is: there should be a lvm thin meta data dump in there, which you could use for benchmarking improvements yourself. > Obviously any pause, even a few seconds is unacceptable. Having a > background kernel worker thread doing the delete, as you describe, is > the way to go. But there are complications to do with > transactionality and crash protection that have prevented me > implementing it. I'll think on it some more now I know it's such a > problem for you. > > - Joe Thanks, Lars -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
