Re: when an osd is started up, IO will be blocked

[wangsongbo <songbo1227@gmail.com>]

Hi all,

When an osd is started, I will get a lot of slow requests from the 
corresponding osd log, as follows:

2015-10-26 03:42:51.593961 osd.4 [WRN] slow request 3.967808 seconds 
old, received at 2015-10-26 03:42:47.625968: 
osd_repop(client.2682003.0:2686048 43.fcf 
d1ddfcf/rbd_data.196483222ac2db.0000000000000010/head//43 v 9744'347845) 
currently commit_sent
2015-10-26 03:42:51.593964 osd.4 [WRN] slow request 3.964537 seconds 
old, received at 2015-10-26 03:42:47.629239: 
osd_repop(client.2682003.0:2686049 43.b4b 
cbcbbb4b/rbd_data.196483222ac2db.000000000000020b/head//43 v 
9744'193029) currently commit_sent
2015-10-26 03:42:52.594166 osd.4 [WRN] 40 slow requests, 17 included 
below; oldest blocked for > 53.692556 secs
2015-10-26 03:42:52.594172 osd.4 [WRN] slow request 2.272928 seconds 
old, received at 2015-10-26 03:42:50.321151: 
osd_repop(client.3684690.0:191908 43.540 
f1858540/rbd_data.1fc5ca7429fc17.0000000000000280/head//43 v 9744'63645) 
currently commit_sent
2015-10-26 03:42:52.594175 osd.4 [WRN] slow request 2.270618 seconds 
old, received at 2015-10-26 03:42:50.323461: 
osd_op(client.3684690.0:191911 rbd_data.1fc5ca7429fc17.0000000000000209 
[write 2633728~4096] 43.72b9f039 ack+ondisk+write e9744) currently 
commit_sent
2015-10-26 03:42:52.594264 osd.4 [WRN] slow request 4.968252 seconds 
old, received at 2015-10-26 03:42:47.625828: 
osd_repop(client.2682003.0:2686047 43.b4b 
cbcbbb4b/rbd_data.196483222ac2db.000000000000020b/head//43 v 
9744'193028) currently commit_sent
2015-10-26 03:42:52.594266 osd.4 [WRN] slow request 4.968111 seconds 
old, received at 2015-10-26 03:42:47.625968: 
osd_repop(client.2682003.0:2686048 43.fcf 
d1ddfcf/rbd_data.196483222ac2db.0000000000000010/head//43 v 9744'347845) 
currently commit_sent
2015-10-26 03:42:52.594318 osd.4 [WRN] slow request 4.964841 seconds 
old, received at 2015-10-26 03:42:47.629239: 
osd_repop(client.2682003.0:2686049 43.b4b 
cbcbbb4b/rbd_data.196483222ac2db.000000000000020b/head//43 v 
9744'193029) currently commit_sent
2015-10-26 03:42:53.594527 osd.4 [WRN] 40 slow requests, 16 included 
below; oldest blocked for > 54.692945 secs
2015-10-26 03:42:53.594533 osd.4 [WRN] slow request 16.004669 seconds 
old, received at 2015-10-26 03:42:37.589800: 
osd_repop(client.2682003.0:2686041 43.b4b 
cbcbbb4b/rbd_data.196483222ac2db.000000000000020b/head//43 v 
9744'193024) currently commit_sent
2015-10-26 03:42:53.594536 osd.4 [WRN] slow request 16.003889 seconds 
old, received at 2015-10-26 03:42:37.590580: 
osd_repop(client.2682003.0:2686040 43.fcf 
d1ddfcf/rbd_data.196483222ac2db.0000000000000010/head//43 v 9744'347842) 
currently commit_sent
2015-10-26 03:42:53.594538 osd.4 [WRN] slow request 16.000954 seconds 
old, received at 2015-10-26 03:42:37.593515: 
osd_repop(client.2682003.0:2686042 43.b4b 
cbcbbb4b/rbd_data.196483222ac2db.000000000000020b/head//43 v 
9744'193025) currently commit_sent
2015-10-26 03:42:53.594541 osd.4 [WRN] slow request 29.138828 seconds 
old, received at 2015-10-26 03:42:24.455641: 
osd_repop(client.4764855.0:65121 43.dbe 
169a9dbe/rbd_data.49a7a4633ac0b1.0000000000000021/head//43 v 9744'12509) 
currently commit_sent
2015-10-26 03:42:53.594543 osd.4 [WRN] slow request 15.998814 seconds 
old, received at 2015-10-26 03:42:37.595656: 
osd_repop(client.1800547.0:1205399 43.cc5 
9285ecc5/rbd_data.1b794560c6e2ea.00000000000000d0/head//43 v 9744'36732) 
currently commit_sent
2015-10-26 03:42:54.594892 osd.4 [WRN] 39 slow requests, 17 included 
below; oldest blocked for > 55.693227 secs
2015-10-26 03:42:54.594908 osd.4 [WRN] slow request 4.273600 seconds 
old, received at 2015-10-26 03:42:50.321151: 
osd_repop(client.3684690.0:191908 43.540 
f1858540/rbd_data.1fc5ca7429fc17.0000000000000280/head//43 v 9744'63645) 
currently commit_sent
2015-10-26 03:42:54.594911 osd.4 [WRN] slow request 4.271290 seconds 
old, received at 2015-10-26 03:42:50.323461: 
osd_op(client.3684690.0:191911 rbd_data.1fc5ca7429fc17.0000000000000209 
[write 2633728~4096] 43.72b9f039 ack+ondisk+write e9744) currently 
commit_sent

Meanwhile, I run fio process with the rbd ioengine.
The iops of read and write were too small to response any IO from the 
fio process,
In other words, when an osd is started, the IO of the whole cluster will 
be blocked.
Is there some parameter to adjust ?
How to explain this  problem?
The results of running fio process were as fllows:

ebs: (g=0): rw=randrw, bs=8K-8K/8K-8K/8K-8K, ioengine=rbd, iodepth=64
fio-2.2.9-20-g1520
Starting 1 thread
rbd engine: RBD version: 0.1.9
Jobs: 1 (f=1): [m(1)] [0.3% done] [0KB/0KB/0KB /s] [0/0/0 iops] [eta 
05h:10m:14s]
ebs: (groupid=0, jobs=1): err= 0: pid=40323: Mon Oct 26 04:02:00 2015
   read : io=10904KB, bw=175183B/s, *iops=21*, runt= 63737msec
     slat (usec): min=0, max=61, avg= 1.11, stdev= 3.16
     clat (msec): min=1, max=63452, avg=1190.04, stdev=6046.28
      lat (msec): min=1, max=63452, avg=1190.04, stdev=6046.28
     clat percentiles (msec):
      |  1.00th=[    3],  5.00th=[    4], 10.00th=[    5], 20.00th=[    6],
      | 30.00th=[    6], 40.00th=[    7], 50.00th=[    8], 60.00th=[    9],
      | 70.00th=[   10], 80.00th=[   12], 90.00th=[   14], 95.00th=[ 709],
      | 99.00th=[16712], 99.50th=[16712], 99.90th=[16712], 99.95th=[16712],
      | 99.99th=[16712]
     bw (KB  /s): min=  129, max= 2038, per=100.00%, avg=774.00, 
stdev=1094.73
   write: io=24976KB, bw=401264B/s,*iops=48,* runt= 63737msec
     slat (usec): min=0, max=40, avg= 2.48, stdev= 3.30
     clat (msec): min=2, max=31379, avg=786.91, stdev=4829.02
      lat (msec): min=2, max=31379, avg=786.92, stdev=4829.02
     clat percentiles (msec):
      |  1.00th=[    4],  5.00th=[    6], 10.00th=[    6], 20.00th=[    8],
      | 30.00th=[    9], 40.00th=[    9], 50.00th=[   11], 60.00th=[   12],
      | 70.00th=[   13], 80.00th=[   15], 90.00th=[   19], 95.00th=[   29],
      | 99.00th=[16712], 99.50th=[16712], 99.90th=[16712], 99.95th=[16712],
      | 99.99th=[16712]
     bw (KB  /s): min=  317, max= 5228, per=100.00%, avg=1957.33, 
stdev=2832.48
     lat (msec) : 2=0.07%, 4=3.23%, 10=52.29%, 20=35.76%, 50=4.41%
     lat (msec) : 750=1.36%, 1000=0.02%, 2000=0.02%, >=2000=2.83%
   cpu          : usr=0.03%, sys=0.00%, ctx=228, majf=0, minf=19
   IO depths    : 1=0.1%, 2=0.1%, 4=0.4%, 8=3.9%, 16=18.9%, 32=73.1%, 
 >=64=3.5%
      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=97.5%, 8=0.0%, 16=0.2%, 32=0.9%, 64=1.5%, 
 >=64=0.0%
      issued    : total=r=1363/w=3122/d=0, short=r=0/w=0/d=0, 
drop=r=0/w=0/d=0
      latency   : target=0, window=0, percentile=100.00%, depth=64

Run status group 0 (all jobs):
    READ: io=10904KB, aggrb=171KB/s, minb=171KB/s, maxb=171KB/s, 
mint=63737msec, maxt=63737msec
   WRITE: io=24976KB, aggrb=391KB/s, minb=391KB/s, maxb=391KB/s, 
mint=63737msec, maxt=63737msec

Disk stats (read/write):
     dm-0: ios=81/34, merge=0/0, ticks=472/26, in_queue=498, util=0.30%, 
aggrios=143/102, aggrmerge=106/122, aggrticks=1209/134, 
aggrin_queue=1343, aggrutil=0.60%
   sdd: ios=143/102, merge=106/122, ticks=1209/134, in_queue=1343, 
util=0.60%


Thanks and Regards,
WangSongbo

On 15/10/22 下午10:43, wangsongbo wrote:
> Hi all,
>
> When an osd is started, relative IO will be blocked.
> According to the test result,the larger iops the clients send , the 
> longer it will take to elapse.
> Adjustment on all the parameters associate with recovery operations 
> was also found useless.
>
> How to reduce the impact of this process on the IO ?
>
> Thanks and Regards,
> WangSongbo
>

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