Re: CRC algorithm selection

[Alexandre DERUMIER <aderumier@odiso.com>]

Hi Sommath, nice debug !

>>BTW, I think we need to error out configure script (or at least document ) if build server is not having 'yasm' installed. 

I have found a redhat bugzilla about ceph and yasm.

https://bugzilla.redhat.com/show_bug.cgi?id=1190882

Seem to be blocked by SELinux.


----- Mail original -----
De: "Somnath Roy" <Somnath.Roy@sandisk.com>
À: "ceph-devel" <ceph-devel@vger.kernel.org>
Envoyé: Mercredi 6 Mai 2015 20:36:35
Objet: CRC algorithm selection

Sage, 
Based on the discussion of today's performance meeting, I ran the crc32 unittest and here is the result. 

root@emsserver2:/home/ceph-main/src# ./unittest_crc32c 
Running main() from gmock_main.cc 
[==========] Running 7 tests from 1 test case. 
[----------] Global test environment set-up. 
[----------] 7 tests from Crc32c 
[ RUN ] Crc32c.Small 
[ OK ] Crc32c.Small (0 ms) 
[ RUN ] Crc32c.PartialWord 
[ OK ] Crc32c.PartialWord (0 ms) 
[ RUN ] Crc32c.Big 
[ OK ] Crc32c.Big (16 ms) 
[ RUN ] Crc32c.Performance 
populating large buffer 
calculating crc 
best choice = 1193.86 MB/sec 
best choice 0xffffffff = 1193.56 MB/sec 
sctp = 1190.6 MB/sec 
intel baseline = 261.623 MB/sec 
[ OK ] Crc32c.Performance (7064 ms) 
[ RUN ] Crc32c.Range 
[ OK ] Crc32c.Range (0 ms) 
[ RUN ] Crc32c.RangeZero 
[ OK ] Crc32c.RangeZero (0 ms) 
[ RUN ] Crc32c.RangeNull 
[ OK ] Crc32c.RangeNull (0 ms) 
[----------] 7 tests from Crc32c (7080 ms total) 

[----------] Global test environment tear-down 
[==========] 7 tests from 1 test case ran. (7080 ms total) 
[ PASSED ] 7 tests. 


So, it seems 'sctp' is giving better performance and thus it is recommending this. 

So, it seems it is not picking up *_intel_fast method and going back to make file I saw 'configure' was skipping yasm check since in my setup yasm was not installed. 
I manually installed 'yasm' and rebuild everything. Now, here is the result..It is picking up *_intel_fast method and it is ~6 times faster !!! 


root@emsserver2:/home/ceph-main/src# ./unittest_crc32c 
Running main() from gmock_main.cc 
[==========] Running 7 tests from 1 test case. 
[----------] Global test environment set-up. 
[----------] 7 tests from Crc32c 
[ RUN ] Crc32c.Small 
[ OK ] Crc32c.Small (0 ms) 
[ RUN ] Crc32c.PartialWord 
[ OK ] Crc32c.PartialWord (0 ms) 
[ RUN ] Crc32c.Big 
[ OK ] Crc32c.Big (4 ms) 
[ RUN ] Crc32c.Performance 
populating large buffer 
calculating crc 
best choice = 6275.01 MB/sec 
best choice 0xffffffff = 6314.59 MB/sec 
sctp = 1187.1 MB/sec 
intel baseline = 261.652 MB/sec 
[ OK ] Crc32c.Performance (5709 ms) 
[ RUN ] Crc32c.Range 
[ OK ] Crc32c.Range (0 ms) 
[ RUN ] Crc32c.RangeZero 
[ OK ] Crc32c.RangeZero (0 ms) 
[ RUN ] Crc32c.RangeNull 
[ OK ] Crc32c.RangeNull (0 ms) 
[----------] 7 tests from Crc32c (5713 ms total) 

[----------] Global test environment tear-down 
[==========] 7 tests from 1 test case ran. (5713 ms total) 
[ PASSED ] 7 tests. 


Thanks for the pointer and I will enable my journal tests with crc enabled. 

BTW, I think we need to error out configure script (or at least document ) if build server is not having 'yasm' installed. 

Thanks & Regards 
Somnath 

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