Jens, Per the "rq_affinity doesn't seem to work?" thread [1]. We found that the default cpu steering that rq_affinity performs is insufficient to keep up with some completion loads. Dave collected the following relative iops measures: pre-patches rq_affinity=0: 1x pre-patches rq_affinity=1: 1x post-patches rq_affinity=1: 1.08x post-patches rq_affinity=2: 1.35x The "adaptive rq_affinity" patch is more of a discussion point than a real fix. However, it shows that even something straightforward and seemingly aggressive does not really come close to the performance of just turning cpu grouping off altogether. The "strict rq_affinity" patch follows the "nomerges" interface precedent of setting 2 to indicate "I really mean it". So, at a minimum consider taking patch 1, and we can leave the search for a better adaptive algorithm as future work. [1]: http://marc.info/?l=linux-kernel&m=131049742925413&w=4 --- Dan Williams (2): block: strict rq_affinity block: adaptive rq_affinity Documentation/block/queue-sysfs.txt | 10 +++++++--- block/blk-core.c | 6 ++---- block/blk-softirq.c | 23 ++++++++++++++++++----- block/blk-sysfs.c | 13 +++++++++---- include/linux/blkdev.h | 3 ++- 5 files changed, 38 insertions(+), 17 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
