Re: speed decrease since firefly,giant,hammer the 2nd try

[Mark Nelson <mnelson@redhat.com>]

On 02/10/2015 04:18 PM, Stefan Priebe wrote:
>
> Am 10.02.2015 um 22:38 schrieb Mark Nelson:
>> On 02/10/2015 03:11 PM, Stefan Priebe wrote:
>>>
>>> mhm i installed librbd1-dbg and librados2-dbg - but the output still
>>> looks useless to me. Should i upload it somewhere?
>>
>> Meh, if it's all just symbols it's probably not that helpful.
>>
>> I've summarized your results here:
>>
>> 1 concurrent 4k write (libaio, direct=1, iodepth=1)
>>
>>          IOPS        Latency
>>          wb on    wb off    wb on    wb off
>> dumpling    10870    536    ~100us    ~2ms
>> firefly        10350    525    ~100us    ~2ms
>>
>> So in single op tests dumpling and firefly are far closer.  Now let's
>> see each of these cases with iodepth=32 (still 1 thread for now).
>
>
> dumpling:
>
> file1: (g=0): rw=randwrite, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=32
> 2.0.8
> Starting 1 thread
> Jobs: 1 (f=1): [w] [100.0% done] [0K/72812K /s] [0 /18.3K iops] [eta
> 00m:00s]
> file1: (groupid=0, jobs=1): err= 0: pid=3011
>    write: io=2060.6MB, bw=70329KB/s, iops=17582 , runt= 30001msec
>      slat (usec): min=1 , max=3517 , avg= 3.42, stdev= 7.30
>      clat (usec): min=93 , max=7475 , avg=1815.72, stdev=233.43
>       lat (usec): min=219 , max=7477 , avg=1819.27, stdev=233.52
>      clat percentiles (usec):
>       |  1.00th=[ 1480],  5.00th=[ 1576], 10.00th=[ 1608], 20.00th=[ 1672],
>       | 30.00th=[ 1704], 40.00th=[ 1752], 50.00th=[ 1800], 60.00th=[ 1832],
>       | 70.00th=[ 1896], 80.00th=[ 1960], 90.00th=[ 2064], 95.00th=[ 2128],
>       | 99.00th=[ 2352], 99.50th=[ 2448], 99.90th=[ 4704], 99.95th=[ 5344],
>       | 99.99th=[ 7072]
>      bw (KB/s)  : min=59696, max=77840, per=100.00%, avg=70351.27,
> stdev=4783.25
>      lat (usec) : 100=0.01%, 250=0.01%, 500=0.01%, 750=0.01%, 1000=0.53%
>      lat (msec) : 2=85.02%, 4=14.31%, 10=0.13%
>    cpu          : usr=1.96%, sys=6.71%, ctx=22791, majf=0, minf=133
>    IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%,
>  >=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=0.1%, 64=0.0%,
>  >=64=0.0%
>       issued    : total=r=0/w=527487/d=0, short=r=0/w=0/d=0
>
> Run status group 0 (all jobs):
>    WRITE: io=2060.6MB, aggrb=70329KB/s, minb=70329KB/s, maxb=70329KB/s,
> mint=30001msec, maxt=30001msec
>
> Disk stats (read/write):
>    sdb: ios=166/526079, merge=0/0, ticks=24/890120, in_queue=890064,
> util=98.73%
>
> firefly:
>
> file1: (g=0): rw=randwrite, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=32
> 2.0.8
> Starting 1 thread
> Jobs: 1 (f=1): [w] [100.0% done] [0K/69096K /s] [0 /17.3K iops] [eta
> 00m:00s]
> file1: (groupid=0, jobs=1): err= 0: pid=2982
>    write: io=1784.9MB, bw=60918KB/s, iops=15229 , runt= 30002msec
>      slat (usec): min=1 , max=1389 , avg= 3.43, stdev= 5.32
>      clat (usec): min=117 , max=8235 , avg=2096.88, stdev=396.30
>       lat (usec): min=540 , max=8258 , avg=2100.43, stdev=396.61
>      clat percentiles (usec):
>       |  1.00th=[ 1608],  5.00th=[ 1720], 10.00th=[ 1768], 20.00th=[ 1832],
>       | 30.00th=[ 1896], 40.00th=[ 1944], 50.00th=[ 2008], 60.00th=[ 2064],
>       | 70.00th=[ 2160], 80.00th=[ 2256], 90.00th=[ 2512], 95.00th=[ 2896],
>       | 99.00th=[ 3600], 99.50th=[ 3792], 99.90th=[ 5088], 99.95th=[ 6304],
>       | 99.99th=[ 6752]
>      bw (KB/s)  : min=36717, max=73712, per=99.94%, avg=60879.92,
> stdev=8302.27
>      lat (usec) : 250=0.01%, 750=0.01%
>      lat (msec) : 2=48.56%, 4=51.18%, 10=0.26%
>    cpu          : usr=2.03%, sys=5.48%, ctx=20440, majf=0, minf=133
>    IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%,
>  >=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=0.1%, 64=0.0%,
>  >=64=0.0%
>       issued    : total=r=0/w=456918/d=0, short=r=0/w=0/d=0
>
> Run status group 0 (all jobs):
>    WRITE: io=1784.9MB, aggrb=60918KB/s, minb=60918KB/s, maxb=60918KB/s,
> mint=30002msec, maxt=30002msec
>
> Disk stats (read/write):
>    sdb: ios=166/455574, merge=0/0, ticks=12/897748, in_queue=897696,
> util=98.96%
>

Ok, so it looks like as you increase concurrency the effect increases 
(ie contention?).  Does the same thing happen without cache enabled?