From: Joe Thornber <thornber@redhat.com>
To: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: device-mapper development <dm-devel@redhat.com>
Subject: Re: I/O block when removing thin device on the same pool
Date: Fri, 29 Jan 2016 16:04:21 +0000 [thread overview]
Message-ID: <20160129160420.GA23215@rh-vpn> (raw)
In-Reply-To: <20160129145031.GD32614@soda.linbit>
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.
next prev parent reply other threads:[~2016-01-29 16:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-20 10:05 I/O block when removing thin device on the same pool Dennis Yang
2016-01-20 11:27 ` Zdenek Kabelac
2016-01-20 16:17 ` Dennis Yang
2016-01-21 17:33 ` Nikolay Borisov
2016-01-21 19:44 ` Mike Snitzer
2016-01-22 13:38 ` Lars Ellenberg
2016-01-22 13:58 ` Zdenek Kabelac
2016-01-22 16:07 ` Mike Snitzer
2016-01-22 16:43 ` Joe Thornber
2016-01-25 9:13 ` Dennis Yang
2016-01-26 16:19 ` Joe Thornber
2016-01-27 4:51 ` Dennis Yang
2016-01-28 10:44 ` Joe Thornber
2016-01-29 11:01 ` Dennis Yang
2016-01-29 16:05 ` Joe Thornber
2016-02-01 3:52 ` Dennis Yang
2016-01-29 14:50 ` Lars Ellenberg
2016-01-29 16:04 ` Joe Thornber [this message]
2016-02-01 17:40 ` Lars Ellenberg
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