Re: [Qemu-devel] [PATCH 0/6] crypto: improve performance of XTS cipher mode

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Oct 09, 2018 at 05:59:46PM +0400, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Oct 9, 2018 at 4:57 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > The XTS cipher mode is significantly slower than CBC mode. This series
> > approximately doubles the XTS performance which will improve the I/O
> > rate for LUKS disks.
> >
> > Daniel P. Berrangé (6):
> >   crypto: expand algorithm coverage for cipher benchmark
> >   crypto: remove code duplication in tweak encrypt/decrypt
> >   crypto: introduce a xts_uint128 data type
> >   crypto: convert xts_tweak_encdec to use xts_uint128 type
> >   crypto: convert xts_mult_x to use xts_uint128 type
> >   crypto: annotate xts_tweak_encdec as inlineable
> >
> >  crypto/xts.c                    | 147 ++++++++++++++-----------------
> >  tests/benchmark-crypto-cipher.c | 149 +++++++++++++++++++++++++++-----
> >  2 files changed, 191 insertions(+), 105 deletions(-)
> 
> By using a constant amount of data to process, it's easier to measure
> perfomance with perf stat:

The problem is that the different encryption modes have wildly
different performance. eg while XTS gets 400 MB/s, ECB gets
3000 MB/s. I want the test to run long enough to minimize the
noise, and picking a data size large enough for best ECB
perf while not being excessively large for XTS is hard. THus
I prefer to have a fixed execution time for each test.


Regards,
Daniel
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