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Re: [dm-devel] [PATCH 8/9] dm crypt: offload writes to thread



On Tue, Apr 01 2014 at 12:27pm -0400,
Ondrej Kozina <okozina redhat com> wrote:

> On 03/28/2014 09:11 PM, Mike Snitzer wrote:
> >From: Mikulas Patocka <mpatocka 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?


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