On Fri, Aug 07 2009, Jens Axboe wrote: > On Fri, Aug 07 2009, Jens Axboe wrote: > > > I'm not NAK'ing... just inserting some relevant NAPI field experience, > > > and hoping for some numbers that better measure the costs/benefits. > > > > Appreciate you looking over this, and I'll certainly be posting some > > more numbers on this. It'll largely depend on both storage, controller, > > and worload. > > Here's a quick set of numbers, beating with random reads on a drive. > Average of three runs for each, stddev is very low so confidence in the > numbers should be high. > > With iopoll=0 (disabled), stock: > > blocksize IOPS ints/sec usr sys > ------------------------------------------------------ > 4k 48401 ~30500 3.36% 27.26% > > clat (usec): min=1052, max=21615, avg=10541.48, stdev=243.48 > clat (usec): min=1066, max=22040, avg=10543.69, stdev=242.05 > clat (usec): min=1057, max=23237, avg=10529.04, stdev=239.30 > > > With iopoll=1 > > blocksize IOPS ints/sec usr sys > ------------------------------------------------------ > 4k 48452 ~29000 3.37% 26.47% > > > clat (usec): min=1178, max=21662, avg=10542.72, stdev=247.87 > clat (usec): min=1074, max=21783, avg=10534.14, stdev=240.54 > clat (usec): min=1102, max=22123, avg=10509.42, stdev=225.73 Lets raise the bar a bit, this time using 8k reads on the faster box. iopoll=0 blocksize IOPS ints/sec usr sys ------------------------------------------------------ 8k 64050 ~76000 4.12% 45.01% clat (usec): min=1326, max=18994, avg=7967.54, stdev=214.12 clat (usec): min=1325, max=25404, avg=7968.06, stdev=239.87 clat (usec): min=1273, max=21414, avg=7963.43, stdev=231.27 iopoll=1 blocksize IOPS ints/sec usr sys ------------------------------------------------------ 8k 64162 ~55000 4.07% 42.32% clat (usec): min=1380, max=19681, avg=7960.31, stdev=197.41 clat (usec): min=1370, max=37508, avg=7954.61, stdev=210.35 clat (usec): min=1332, max=23383, avg=7947.99, stdev=209.60 Again, purely a synthetic IO benchmark, but the sys reduction is interesting. -- Jens Axboe -- 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
