On Fri, Jan 29, 2016 at 03:50:31PM +0100, Lars Ellenberg wrote: > 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. There is no metadata dump attached to that bug. I do benchmark stuff myself, and I found prefetching to make a big difference (obviously I'm not cpu bound like you). We all have different hardware, which is why I ask people with more real world scenarios to test stuff separately. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
