On Oct 23, 2014 9:05 PM, "George Smith" <glsmith555@xxxxxxxxx> wrote: > > Uh oh, silence is never good :) Please let me know if I haven't > included key information, missed something obvious, etc. > > Here's maybe a clearer example of what I'm talking about. The output > file is from a read test using 5 threads: > > # grep 'read :' output.out > read : io=51200MB, bw=116673KB/s, iops=113 , runt=449367msec > read : io=51200MB, bw=189201KB/s, iops=184 , runt=277106msec > read : io=51200MB, bw=143385KB/s, iops=140 , runt=365650msec > read : io=51200MB, bw=114654KB/s, iops=111 , runt=457279msec > read : io=51200MB, bw=183110KB/s, iops=178 , runt=286324msec > > # grep READ output.out > READ: io=256000MB, aggrb=573269KB/s, minb=114653KB/s, > maxb=189201KB/s, mint=277106msec, maxt=457279msec > > > The sum of the threads is 747023, but aggrb is 573269. The bw= value > in each thread line is the amount of I/O (from io=) divided by the > time the I/O took. > > The aggrb= value is the total amount of I/O done (which is the sum of > each thread's io= value), divided by maxt, which seems to be the > maximum time seen during the run (which happens to be with my 4th > thread). Looking at the code (https://github.com/axboe/fio/blob/master/stat.c), that's exactly what it does. > > So it appears that this is the discrepancy. I'm not sure if it's > correct to say the aggregate bandwidth is the total I/O divided by the > max time that one of the threads in the group took to complete. Seems > like taking the average time and dividing total I/O by that would be > more correct. Aggregate bandwidth is presumably what the device might sustain when all threads are active. If all threads ran for about the same time, those two metrics would give more or less the same answer. If there is a substantial variation in per thread run time as in your case (I'd look into why, being in your shoes, by the way), talking aggregate bandwidth is hardly justified. My $.02. Regards, Andrey > > Am I missing the spirit of what the READ line is supposed to be conveying to me? > > Thanks, > > --gs > > On Tue, Oct 21, 2014 at 11:55 AM, George Smith <glsmith555@xxxxxxxxx> wrote: > > Hello, > > > > I use multiple threads for read and write tests, and use group > > reporting to see each thread's stats. So in my output file, I have > > something like this: > > > > ----- > > > > JOB: (groupid=0, jobs=1): err= 0: pid=17829: Tue Oct 21 12:36:24 2014 > > Description : [foo] > > write: io=12288MB, bw=30371KB/s, iops=59 , runt=414309msec > > clat (usec): min=297 , max=30868K, avg=16722.93, stdev=321816.10 > > lat (usec): min=297 , max=30868K, avg=16723.20, stdev=321816.11 > > clat percentiles (usec): > > | 1.00th=[ 326], 5.00th=[ 334], 10.00th=[ 338], 20.00th=[ 342], > > | 30.00th=[ 350], 40.00th=[ 358], 50.00th=[ 366], 60.00th=[ 386], > > | 70.00th=[ 410], 80.00th=[ 486], 90.00th=[ 572], 95.00th=[ 668], > > | 99.00th=[45824], 99.50th=[626688], 99.90th=[4554752], 99.95th=[5865472], > > | 99.99th=[10289152] > > bw (KB/s) : min= 16, max=1002496, per=32.23%, avg=78205.35, > > stdev=182341.44 > > lat (usec) : 500=82.77%, 750=13.07%, 1000=0.68% > > lat (msec) : 2=1.42%, 4=0.44%, 10=0.15%, 20=0.23%, 50=0.26% > > lat (msec) : 100=0.15%, 250=0.14%, 500=0.13%, 750=0.09%, 1000=0.08% > > lat (msec) : 2000=0.15%, >=2000=0.24% > > cpu : usr=0.77%, sys=2.91%, ctx=24853, majf=0, minf=4 > > IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% > > submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% > > complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% > > issued : total=r=0/w=24576/d=0, short=r=0/w=0/d=0 > > > > … (another thread) … > > … (another thread) ... > > > > Run status group 0 (all jobs): > > WRITE: io=98304MB, aggrb=242665KB/s, minb=30333KB/s, maxb=44320KB/s, > > mint=283908msec, maxt=414823msec > > > > ----- > > > > > > If I go through and parse each "write" line (in this example), and add > > up all the "bw=" numbers, that does not equal the "aggrb" number > > reported at the end (it's higher by about 15%). > > > > I thought "aggrb" would just be a rollup of all the individual > > thread's bandwidth, so I'm having a hard time determining why the two > > numbers don't match. Maybe my basic assumption is incorrect, and if > > that's true then which numbers are correct -- the per-thread numbers, > > or the aggregate number? > > > > Thanks for any help… > > > > --gs > -- > To unsubscribe from this list: send the line "unsubscribe fio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
