Re: Ext4 and xfs problems in dm-thin on allocation and discard

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Jun 19 2012 at 10:44am -0400,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:

> On Tue, Jun 19 2012 at  9:52am -0400,
> Spelic <spelic@xxxxxxxxxxxxx> wrote:
>
> > I do not know what is the mechanism for which xfs cannot unmap
> > blocks from dm-thin, but it really can't.
> > If anyone has dm-thin installed he can try. This is 100%
> > reproducible for me.
> 
> I was initially surprised by this considering the thinp-test-suite does
> test a compilebench workload against xfs and ext4 using online discard
> (-o discard).
> 
> But I just modified that test to use a thin-pool with 'ignore_discard'
> and the test still passed on both ext4 and xfs.
> 
> So there is more work needed in the thinp-test-suite to use blktrace
> hooks to verify that discards are occuring when the compilebench
> generated files are removed.
> 
> I'll work through that and report back.

blktrace shows discards for both xfs and ext4.

But in general xfs is issuing discards with much smaller extents than
ext4 does, e.g.:

to the thin device:
+ 128 vs + 32

to the thin-pool's data device:
+ 120 vs + 16
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Reiser Filesystem Development]     [Ceph FS]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite National Park]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Device Mapper]     [Linux Media]

  Powered by Linux