Ceph » RADOS

With zero backoffs, just constructing an hobject_t ("hobject_t hoid = op->target.get_hobj();") results in an approximate 10% performance degradation on RBD 4K IO random read tests. Moving the object construction to within the backoff clause where it's used skips the penalty for the cases where there is no backoff from the OSDs.

12.2.1 original fio results:

   bw (  KiB/s): min=119040, max=154472, per=100.00%, avg=146800.00, stdev=9222.50, samples=30
   iops        : min=29760, max=38618, avg=36700.00, stdev=2305.62, samples=30

12.2.1 fio results after skipping the unnecessary construction:

   bw (  KiB/s): min=158688, max=165488, per=100.00%, avg=162691.57, stdev=1706.77, samples=30
   iops        : min=39672, max=41372, avg=40672.87, stdev=426.71, samples=30