Ronald Moesbergen, on 07/28/2009 01:51 PM wrote:
2009/7/27 Vladislav Bolkhovitin <vst@xxxxxxxx>:
Hmm, it's really weird, why the case of 2 threads is faster. There must be
some commands reordering somewhere in SCST, which I'm missing, like
list_add() instead of list_add_tail().
Can you apply the attached patch and repeat tests 5, 8 and 11 with 1 and 2
threads, please. The patch will enable forced commands order protection,
i.e. with it all the commands will be executed in exactly the same order as
they were received.
The patched source doesn't compile. I changed the code to this:
@ line 3184:
case SCST_CMD_QUEUE_UNTAGGED:
#if 1 /* left for future performance investigations */
goto ordered;
#endif
The results:
Overall performance seems lower.
client kernel: 2.6.26-15lenny3 (debian)
server kernel: 2.6.29.5 with readahead-context, blk_run_backing_dev
and io_context, forced_order
With one IO thread:
5) client: default, server: default (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 16.484 16.417 16.068 62.741 0.706 0.980
33554432 15.684 16.348 16.011 63.961 1.083 1.999
16777216 16.044 16.239 15.938 63.710 0.493 3.982
8) client: default, server: 64 max_sectors_kb, RA 2MB (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 16.127 15.784 16.210 63.847 0.740 0.998
33554432 16.103 16.072 16.106 63.627 0.061 1.988
16777216 16.637 16.058 16.154 62.902 0.970 3.931
11) client: 64 max_sectors_kb, 2MB. RA server: 64 max_sectors_kb, RA 2MB (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 13.417 15.219 13.912 72.405 3.785 1.131
33554432 13.868 13.789 14.110 73.558 0.718 2.299
16777216 13.691 13.784 10.280 82.898 11.822 5.181
11) client: 64 max_sectors_kb, 2MB. RA server: 64 max_sectors_kb, RA
2MB (deadline)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 13.604 13.532 13.978 74.733 1.055 1.168
33554432 13.523 13.166 13.504 76.443 0.945 2.389
16777216 13.434 13.409 13.632 75.902 0.557 4.744
With two threads:
5) client: default, server: default (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 16.206 16.001 15.908 63.851 0.493 0.998
33554432 16.927 16.033 15.991 62.799 1.631 1.962
16777216 16.566 15.968 16.212 63.035 0.950 3.940
8) client: default, server: 64 max_sectors_kb, RA 2MB (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 16.017 15.849 15.748 64.521 0.450 1.008
33554432 16.652 15.542 16.259 63.454 1.823 1.983
16777216 16.456 16.071 15.943 63.392 0.849 3.962
11) client: 64 max_sectors_kb, 2MB. RA server: 64 max_sectors_kb, RA 2MB (cfq)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 14.109 9.985 13.548 83.572 13.478 1.306
33554432 13.698 14.236 13.754 73.711 1.267 2.303
16777216 13.610 12.090 14.136 77.458 5.244 4.841
11) client: 64 max_sectors_kb, 2MB. RA server: 64 max_sectors_kb, RA
2MB (deadline)
blocksize R R R R(avg, R(std R
(bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
67108864 13.542 13.975 13.978 74.049 1.110 1.157
33554432 9.921 13.272 13.321 85.746 12.349 2.680
16777216 13.850 13.600 13.344 75.324 1.144 4.708
Can you perform the tests 5 and 8 the deadline? I asked for deadline..
What I/O scheduler do you use on the initiator? Can you check if
changing it to deadline or noop makes any difference?
Thanks,
Vlad
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