[dm-devel] [PATCH 8/9] dm crypt: offload writes to thread
Mikulas Patocka
mpatocka at redhat.com
Tue Apr 1 18:15:54 UTC 2014
On Tue, 1 Apr 2014, Mike Snitzer wrote:
> On Tue, Apr 01 2014 at 12:27pm -0400,
> Ondrej Kozina <okozina at redhat.com> wrote:
>
> > On 03/28/2014 09:11 PM, Mike Snitzer wrote:
> > >From: Mikulas Patocka <mpatocka at redhat.com>
> > >
> > >Submitting write bios directly in the encryption thread caused serious
> > >performance degradation. On a multiprocessor machine, encryption requests
> > >finish in a different order than they were submitted. Consequently, write
> > >requests would be submitted in a different order and it could cause severe
> > >performance degradation.
> > > (...)
> >
> > Hi,
> >
> > originally I planed to post result of performance testing but
> > unfortunately I crashed the test machine several times with
> > <in_subject> patch applied and onward:
> >
> > The test set up looks following:
> >
> > the base is kernel-3.14-rc8 with applied "[PATCH 2/9] block: use
> > kmalloc alignment for bio slab"
> >
> > On top of base I compiled various dm-crypt modules:
> >
> > <no_patch> = raw 3.14-rc8 dm-crypt module
> > <no_percpu> = "[PATCH 1/9]"
> > <per_bio_data> = <no_percpu> + "[PATCH 3/9]"
> > <unbound> = <per_bio_data> + "[PATCH 4/9]"
> > <dont_allocate_wfix> = <unbound> + "[PATCH 5/9]" + "[PATCH 6/9]"
> > <remove_io_pool> = <dont_allocate_wfix> + "[PATCH 7/9]"
> > <offload> = <remove_io_pool> + "[PATCH 8/9]"
> > <sort> = <offload> + "[PATCH 9/9]"
>
> Wonder if it worthwhile to rebase to final v3.14... could this
> bio_add_page/mm crash be a function of something since fixed late in the
> rc cycle?
... or try it without XFS. XFS corrupts memory on I/O error
(https://bugzilla.redhat.com/show_bug.cgi?id=924301), so it may be that.
Can the bug be reproduced if you modify the test to use ext2, ext3 or ext4
instead of xfs?
Mikulas
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