Re: CEPH Erasure Encoding + OSD Scalability

* RE: CEPH Erasure Encoding + OSD Scalability
@ 2013-09-22 23:00 Andreas Joachim Peters
  2013-09-23  7:27 ` Loic Dachary
  0 siblings, 1 reply; 52+ messages in thread
From: Andreas Joachim Peters @ 2013-09-22 23:00 UTC (permalink / raw)
  To: Loic Dachary; +Cc: ceph-devel

Hi Loic, 
I was applying the changes and the 
situation improves, however there is still one important thing which 
actually dominated all the measurements which were needing larger packet
 sizes (everything besides Raid6):

                     pad_in_length(unsigned in_length)

The implementation is sort of 'unlucky' and slow when one increases the packetsize.

   while (in_length%(k*w*packetsize*sizeof(int)) != 0)
      in_length++;

better do like this:

  alignment = k*w*packetsize*sizeof(int);
  in_length += (alignment - (in_length%alignment);

E.g. for the CauchyGood algorithm one should increase the packetsize and when changing the pad_in_length 
implementation one get's excellent (pure encoding) performance for (3+2) : 2.6 GB/s and it scales well with the number of core's to > 8 GB/s.

I compared this with the output of the 'encode' example of the jerasure
 example and it gives the same result for (3+2), so that looks now good 
and consistent! (10,4) is ~ 610 MB/s.

... 
Finally the description of Jerasure 2.0 looks really great and will probably shift all the performance problems upstream  ;-)

Do you evt. want to add support into the plugin for local parities (like Xorbas does) to improve the disk draining performance?

Cheers Andreas.

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