Re: reads while 100% write

* Re: reads while 100% write
@ 2016-03-30 20:02 Sage Weil
  2016-03-30 20:29 ` Jason Dillaman
  0 siblings, 1 reply; 16+ messages in thread
From: Sage Weil @ 2016-03-30 20:02 UTC (permalink / raw)
  To: Jason Dillaman; +Cc: Evgeniy Firsov, ceph-devel

[-- Attachment #1: Type: TEXT/PLAIN, Size: 10033 bytes --]

On Wed, 30 Mar 2016, Jason Dillaman wrote:
> This IO is being performed within an OSD class method.  I can add a new 
> cls_cxx_read2 method to accept cache hints and update the associated 
> object map methods.  Would this apply to writes as well?

Yeah, we'll want to hint them both.

s

> 
> -- 
> 
> Jason Dillaman 
> 
> 
> ----- Original Message -----
> > From: "Sage Weil" <sage@newdream.net>
> > To: "Jason Dillaman" <dillaman@redhat.com>
> > Cc: "Evgeniy Firsov" <Evgeniy.Firsov@sandisk.com>, ceph-devel@vger.kernel.org
> > Sent: Wednesday, March 30, 2016 3:55:14 PM
> > Subject: Re: reads while 100% write
> > 
> > On Wed, 30 Mar 2016, Jason Dillaman wrote:
> > > Are you using the RBD default of 4MB object sizes or are you using
> > > something much smaller like 64KB?  An object map of that size should be
> > > tracking up to 24,576,000 objects.  When you ran your test before, did
> > > you have the RBD object map disabled?  This definitely seems to be a use
> > > case where the lack of a cache in front of BlueStore is hurting small
> > > IO.
> > 
> > Using the rados cache hint WILLNEED is probably appropriate here..
> > 
> > sage
> > 
> > > 
> > > --
> > > 
> > > Jason Dillaman
> > > 
> > > 
> > > ----- Original Message -----
> > > > From: "Evgeniy Firsov" <Evgeniy.Firsov@sandisk.com>
> > > > To: "Jason Dillaman" <dillaman@redhat.com>
> > > > Cc: "Sage Weil" <sage@newdream.net>, ceph-devel@vger.kernel.org
> > > > Sent: Wednesday, March 30, 2016 3:00:47 PM
> > > > Subject: Re: reads while 100% write
> > > > 
> > > > 1.5T in that run.
> > > > With 150G behavior is the same. Except it says "_do_read 0~18 size
> > > > 615030”
> > > > instead of 6M.
> > > > 
> > > > Also when random 4k write starts there are more reads then writes:
> > > > 
> > > > Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> > > > avgrq-sz
> > > > avgqu-sz   await r_await w_await  svctm  %util
> > > > 
> > > > sdd               0.00  1887.00    0.00  344.00     0.00  8924.00
> > > > 51.88
> > > >     0.36    1.06    0.00    1.06   0.91  31.20
> > > > sde              30.00     0.00   30.00  957.00 18120.00  3828.00
> > > > 44.47
> > > >     0.25    0.26    3.87    0.14   0.17  16.40
> > > > 
> > > > Logs: http://pastebin.com/gGzfR5ez
> > > > 
> > > > 
> > > > On 3/30/16, 11:37 AM, "Jason Dillaman" <dillaman@redhat.com> wrote:
> > > > 
> > > > >How large is your RBD image?  100 terabytes?
> > > > >
> > > > >--
> > > > >
> > > > >Jason Dillaman
> > > > >
> > > > >
> > > > >----- Original Message -----
> > > > >> From: "Evgeniy Firsov" <Evgeniy.Firsov@sandisk.com>
> > > > >> To: "Sage Weil" <sage@newdream.net>
> > > > >> Cc: ceph-devel@vger.kernel.org
> > > > >> Sent: Wednesday, March 30, 2016 2:14:12 PM
> > > > >> Subject: Re: reads while 100% write
> > > > >>
> > > > >> These are suspicious lines:
> > > > >>
> > > > >> 2016-03-30 10:54:23.142205 7f2e933ff700 10 bluestore(src/dev/osd0)
> > > > >> read
> > > > >> 0.d_head #0:b06b5e8e:::rbd_object_map.10046b8b4567:head# 6144018~6012
> > > > >> =
> > > > >> 6012
> > > > >> 2016-03-30 10:54:23.142252 7f2e933ff700 15 bluestore(src/dev/osd0)
> > > > >> read
> > > > >> 0.d_head #0:b06b5e8e:::rbd_object_map.10046b8b4567:head# 8210~4096
> > > > >> 2016-03-30 10:54:23.142260 7f2e933ff700 20 bluestore(src/dev/osd0)
> > > > >> _do_read 8210~4096 size 6150030
> > > > >> 2016-03-30 10:54:23.142267 7f2e933ff700  5 bdev(src/dev/osd0/block)
> > > > >> read
> > > > >> 8003854336~8192
> > > > >> 2016-03-30 10:54:23.142609 7f2e933ff700 10 bluestore(src/dev/osd0)
> > > > >> read
> > > > >> 0.d_head #0:b06b5e8e:::rbd_object_map.10046b8b4567:head# 8210~4096 =
> > > > >>4096
> > > > >> 2016-03-30 10:54:23.142882 7f2e933ff700 15 bluestore(src/dev/osd0)
> > > > >>_write
> > > > >> 0.d_head #0:b06b5e8e:::rbd_object_map.10046b8b4567:head# 8210~4096
> > > > >> 2016-03-30 10:54:23.142888 7f2e933ff700 20 bluestore(src/dev/osd0)
> > > > >> _do_write #0:b06b5e8e:::rbd_object_map.10046b8b4567:head# 8210~4096 -
> > > > >>have
> > > > >> 6150030 bytes in 1 extents
> > > > >>
> > > > >> More logs here: http://pastebin.com/74WLzFYw
> > > > >>
> > > > >>
> > > > >>
> > > > >> On 3/30/16, 4:19 AM, "Sage Weil" <sage@newdream.net> wrote:
> > > > >>
> > > > >> >On Wed, 30 Mar 2016, Evgeniy Firsov wrote:
> > > > >> >> After pulling master branch on Friday I start seeing odd fio
> > > > >>behavior, I
> > > > >> >> see a lot of reads while writing and very low performance no matter
> > > > >> >> whether it read or write workload.
> > > > >> >>
> > > > >> >> Output from sequential 1M write:
> > > > >> >> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> > > > >> >>avgrq-sz
> > > > >> >> avgqu-sz   await r_await w_await  svctm  %util
> > > > >> >>
> > > > >> >> sdd               0.00   409.00    0.00  364.00     0.00  3092.00
> > > > >> >>16.99
> > > > >> >>     0.28    0.78    0.00    0.78   0.76  27.60
> > > > >> >> sde               0.00   242.00  365.00  363.00  2436.00  9680.00
> > > > >> >>33.29
> > > > >> >>     0.18    0.24    0.42    0.07   0.23  16.80
> > > > >> >>
> > > > >> >>
> > > > >> >>
> > > > >> >> block.db -> /dev/sdd
> > > > >> >> block -> /dev/sde
> > > > >> >>
> > > > >> >> health HEALTH_OK
> > > > >> >> monmap e1: 1 mons at {a=127.0.0.1:6789/0}
> > > > >> >>        election epoch 3, quorum 0 a
> > > > >> >> osdmap e7: 1 osds: 1 up, 1 in
> > > > >> >>        flags sortbitwise
> > > > >> >> pgmap v24: 64 pgs, 1 pools, 577 MB data, 9152 objects
> > > > >> >>        8210 MB used, 178 GB / 186 GB avail
> > > > >> >>              64 active+clean
> > > > >> >> client io 1550 kB/s rd, 9559 kB/s wr, 645 op/s rd, 387 op/s wr
> > > > >> >>
> > > > >> >>
> > > > >> >> While on earlier revision(c1e41af) everything looks as expected:
> > > > >> >>
> > > > >> >> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> > > > >> >>avgrq-sz
> > > > >> >> avgqu-sz   await r_await w_await  svctm  %util
> > > > >> >> sdd               0.00  4910.00    0.00  680.00     0.00 22416.00
> > > > >> >>65.93
> > > > >> >>     1.05    1.55    0.00    1.55   1.18  80.00
> > > > >> >> sde               0.00     0.00    0.00 3418.00     0.00 217612.00
> > > > >> >> 127.33    63.78   18.18    0.00   18.18   0.25  86.40
> > > > >> >>
> > > > >> >> Other observation, may be related to the issue, is that CPU load is
> > > > >> >> imbalanced. Single ³tp_osd_tp² thread is 100% busy, while the rest
> > > > >> >> is
> > > > >> >>idle.
> > > > >> >> Looks like all load goes to single thread pool shard, earlier CPU
> > > > >> >> was
> > > > >> >>well
> > > > >> >> balanced.
> > > > >> >
> > > > >> >Hmm.  Can you capture a log with debug bluestore = 20 and debug bdev
> > > > >> >=
> > > > >>20?
> > > > >> >
> > > > >> >Thanks!
> > > > >> >sage
> > > > >> >
> > > > >> >
> > > > >> >>
> > > > >> >>
> > > > >> >> ‹
> > > > >> >> Evgeniy
> > > > >> >>
> > > > >> >>
> > > > >> >>
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