Date: Wed, 20 Aug 2014 11:22:33 -0500 From: "Polyack, Steve" <Steve.Polyack@intermedix.com> To: Alan Cox <alc@rice.edu>, "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: RE: vmdaemon CPU usage and poor performance in 10.0-RELEASE Message-ID: <4D557EC7CC2A544AA7C1A3B9CBA2B3672609CF33F6@exchange03.epbs.com> In-Reply-To: <53F4C82E.5000900@rice.edu> References: <4D557EC7CC2A544AA7C1A3B9CBA2B36726098846B4@exchange03.epbs.com> <20140813152522.GI9400@home.opsec.eu> <4D557EC7CC2A544AA7C1A3B9CBA2B36726098847AF@exchange03.epbs.com> <CAJUyCcNoTJ3xqkC_Prz3N%2BApEqYy3Mi2gA%2BuDo33dczaTMONrA@mail.gmail.com> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609BBA3C4@exchange03.epbs.com> <53F24E5B.1010809@rice.edu> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609BBA64F@exchange03.epbs.com> <53F2790C.20703@rice.edu> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609CF28E5@exchange03.epbs.com> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609CF2F8F@exchange03.epbs.com> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609CF31F0@exchange03.epbs.com> <53F4C4C2.1030109@rice.edu> <4D557EC7CC2A544AA7C1A3B9CBA2B3672609CF335D@exchange03.epbs.com> <53F4C82E.5000900@rice.edu>
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> -----Original Message-----
> From: Alan Cox [mailto:alc@rice.edu]
> Sent: Wednesday, August 20, 2014 12:09 PM
> To: Polyack, Steve; freebsd-stable@freebsd.org
> Subject: Re: vmdaemon CPU usage and poor performance in 10.0-RELEASE
>=20
> On 08/20/2014 10:56, Polyack, Steve wrote:
> >> -----Original Message-----
> >> From: Alan Cox [mailto:alc@rice.edu]
> >> Sent: Wednesday, August 20, 2014 11:55 AM
> >> To: Polyack, Steve; freebsd-stable@freebsd.org
> >> Subject: Re: vmdaemon CPU usage and poor performance in 10.0-RELEASE
> >>
> >> On 08/20/2014 09:55, Polyack, Steve wrote:
> >>>> -----Original Message-----
> >>>> From: Polyack, Steve
> >>>> Sent: Wednesday, August 20, 2014 9:14 AM
> >>>> To: Polyack, Steve; Alan Cox; freebsd-stable@freebsd.org
> >>>> Subject: RE: vmdaemon CPU usage and poor performance in 10.0-
> RELEASE
> >>>>
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: owner-freebsd-stable@freebsd.org [mailto:owner-freebsd-
> >>>>> stable@freebsd.org] On Behalf Of Polyack, Steve
> >>>>> Sent: Tuesday, August 19, 2014 12:37 PM
> >>>>> To: Alan Cox; freebsd-stable@freebsd.org
> >>>>> Subject: RE: vmdaemon CPU usage and poor performance in 10.0-
> >> RELEASE
> >>>>>> -----Original Message-----
> >>>>>> From: owner-freebsd-stable@freebsd.org [mailto:owner-freebsd-
> >>>>>> stable@freebsd.org] On Behalf Of Alan Cox
> >>>>>> Sent: Monday, August 18, 2014 6:07 PM
> >>>>>> To: freebsd-stable@freebsd.org
> >>>>>> Subject: Re: vmdaemon CPU usage and poor performance in 10.0-
> >>>> RELEASE
> >>>>>> On 08/18/2014 16:29, Polyack, Steve wrote:
> >>>>>>>> -----Original Message-----
> >>>>>>>> From: owner-freebsd-stable@freebsd.org [mailto:owner-freebsd-
> >>>>>>>> stable@freebsd.org] On Behalf Of Alan Cox
> >>>>>>>> Sent: Monday, August 18, 2014 3:05 PM
> >>>>>>>> To: freebsd-stable@freebsd.org
> >>>>>>>> Subject: Re: vmdaemon CPU usage and poor performance in 10.0-
> >>>>> RELEASE
> >>>>>>>> On 08/18/2014 13:42, Polyack, Steve wrote:
> >>>>>>>>> Excuse my poorly formatted reply at the moment, but this seems
> to
> >>>>>> have
> >>>>>>>> fixed our problems. I'm going to update the bug report with a
> note.
> >>>>>>>>> Thanks Alan!
> >>>>>>>> You're welcome. And, thanks for letting me know of the outcome.
> >>>>>>>>
> >>>>>>> Actually, I may have spoken too soon, as it looks like we're seei=
ng
> >>>>>> vmdaemon tying up the system again:
> >>>>>>> root 6 100.0 0.0 0 16 - DL Wed0=
4PM 4:37.95
> >>>>> [vmdaemon]
> >>>>>>> Is there anything I can check to help narrow down what may be the
> >>>>>> problem? KTrace/truss on the "process" doesn't give any
> information, I
> >>>>>> suppose because it's actually a kernel thread.
> >>>>>>
> >>>>>> Can you provide the full output of top? Is there anything unusual
> >> about
> >>>>>> the hardware or software configuration?
> >>>>> This may have just been a fluke (maybe NFS caching the old
> >> vm_pageout.c
> >>>>> during the first source build). We've rebuilt and are monitoring i=
t
> now.
> >>>>>
> >>>>> The hardware consists of a few Dell PowerEdge R720xd servers with
> >> 256GB
> >>>>> of RAM and array of SSDs (no ZFS). 64GB is dedicated to postgres
> >>>>> shared_buffers right now. FreeBSD 10, PostgreSQL 9.3, Slony-I v2.2.=
2,
> >> and
> >>>>> redis-2.8.11 are all in use here. I can't say that anything is unu=
sual
> about
> >>>> the
> >>>>> configuration.
> >>>>>
> >>>> We are still seeing the issue. It seems to manifest once the "Free"
> >> memory
> >>>> gets under 10GB (of 256GB on the system), even though ~200GB of this
> is
> >>>> classified as Inactive. For us, this was about 7 hours of database
> activity
> >>>> (initial replication w/ slony). Right now vmdaemon is consuming 100=
%
> >> CPU
> >>>> and shows 671:34 CPU time when it showed 0:00 up until the problem
> >>>> manifested. The full top output (that fits on my screen) is below:
> >>>>
> >>>> last pid: 62309; load averages: 4.05, 4.24, 4.10
> >>>> up 0+22:34:31 09:08:43
> >>>> 159 processes: 8 running, 145 sleeping, 1 waiting, 5 lock
> >>>> CPU: 14.5% user, 0.0% nice, 4.9% system, 0.0% interrupt, 80.5% id=
le
> >>>> Mem: 26G Active, 216G Inact, 4122M Wired, 1178M Cache, 1632M Buf,
> >> 2136M
> >>>> Free
> >>>> Swap: 32G Total, 32G Free
> >>>>
> >>>> PID USERNAME THR PRI NICE SIZE RES STATE C TIME =
WCPU
> >>>> COMMAND
> >>>> 11 root 32 155 ki31 0K 512K CPU31 31 669.6H 293=
4.23% idle
> >>>> 6 root 1 -16 - 0K 16K CPU19 19 678:57 100=
.00% vmdaemon
> >>>> 1963 pgsql 1 45 0 67538M 208M CPU0 0 121:46 17=
.38%
> postgres
> >>>> 2037 pgsql 1 77 0 67536M 2200K *vm ob 14 6:24 15=
.97%
> postgres
> >>>> 1864 pgsql 1 31 0 67536M 1290M semwai 4 174:41 15=
.19%
> >> postgres
> >>>> 1996 pgsql 1 38 0 67538M 202M semwai 16 120:27 15=
.09%
> >> postgres
> >>>> 1959 pgsql 1 39 0 67538M 204M CPU27 27 117:30 15=
.09%
> postgres
> >>>> 1849 pgsql 1 32 0 67536M 1272M semwai 23 126:22 13=
.96%
> >> postgres
> >>>> 1997 pgsql 1 31 0 67538M 206M CPU30 30 122:26 11=
.77%
> postgres
> >>>> 2002 pgsql 1 34 0 67538M 182M sbwait 11 55:20 11=
.28%
> postgres
> >>>> 1961 pgsql 1 32 0 67538M 206M CPU12 12 121:47 10=
.99%
> postgres
> >>>> 1964 pgsql 1 30 0 67538M 206M semwai 28 122:08 9=
.86%
> postgres
> >>>> 1962 pgsql 1 29 0 67538M 1286M sbwait 2 45:49 7=
.18%
> postgres
> >>>> 1752 root 1 22 0 78356K 8688K CPU2 2 175:46 6=
.88% snmpd
> >>>> 1965 pgsql 1 25 0 67538M 207M semwai 9 120:55 6=
.59%
> postgres
> >>>> 1960 pgsql 1 23 0 67538M 177M semwai 6 52:42 4=
.88%
> postgres
> >>>> 1863 pgsql 1 25 0 67542M 388M semwai 25 9:12 2=
.20%
> postgres
> >>>> 1859 pgsql 1 22 0 67538M 1453M *vm ob 20 6:13 2=
.10%
> postgres
> >>>> 1860 pgsql 1 22 0 67538M 1454M sbwait 8 6:08 1=
.95% postgres
> >>>> 1848 pgsql 1 21 0 67586M 66676M *vm ob 30 517:07 1=
.66%
> >> postgres
> >>>> 1856 pgsql 1 22 0 67538M 290M *vm ob 15 5:39 1=
.66%
> postgres
> >>>> 1846 pgsql 1 21 0 67538M 163M sbwait 15 5:46 1=
.46% postgres
> >>>> 1853 pgsql 1 21 0 67538M 110M sbwait 30 8:54 1=
.17% postgres
> >>>> 1989 pgsql 1 23 0 67536M 5180K sbwait 18 1:41 0=
.98% postgres
> >>>> 5 root 1 -16 - 0K 16K psleep 6 9:33 0=
.78% pagedaemon
> >>>> 1854 pgsql 1 20 0 67538M 338M sbwait 22 5:38 0=
.78% postgres
> >>>> 1861 pgsql 1 20 0 67538M 286M sbwait 15 6:13 0=
.68% postgres
> >>>> 1857 pgsql 1 20 0 67538M 1454M semwai 10 6:19 0=
.49%
> postgres
> >>>> 1999 pgsql 1 36 0 67538M 156M *vm ob 28 120:56 0=
.39%
> postgres
> >>>> 1851 pgsql 1 20 0 67538M 136M sbwait 22 5:48 0=
.39% postgres
> >>>> 1975 pgsql 1 20 0 67536M 5688K sbwait 25 1:40 0=
.29% postgres
> >>>> 1858 pgsql 1 20 0 67538M 417M sbwait 3 5:55 0=
.20% postgres
> >>>> 2031 pgsql 1 20 0 67536M 5664K sbwait 5 3:26 0=
.10% postgres
> >>>> 1834 root 12 20 0 71892K 12848K select 20 34:05 0=
.00% slon
> >>>> 12 root 78 -76 - 0K 1248K WAIT 0 25:47 0=
.00% intr
> >>>> 2041 pgsql 1 20 0 67536M 5932K sbwait 14 12:50 0=
.00%
> postgres
> >>>> 2039 pgsql 1 20 0 67536M 5960K sbwait 17 9:59 0=
.00% postgres
> >>>> 2038 pgsql 1 20 0 67536M 5956K sbwait 6 8:21 0=
.00% postgres
> >>>> 2040 pgsql 1 20 0 67536M 5996K sbwait 7 8:20 0=
.00% postgres
> >>>> 2032 pgsql 1 20 0 67536M 5800K sbwait 22 7:03 0=
.00% postgres
> >>>> 2036 pgsql 1 20 0 67536M 5748K sbwait 23 6:38 0=
.00% postgres
> >>>> 1812 pgsql 1 20 0 67538M 59185M select 1 5:46 0=
.00% postgres
> >>>> 2005 pgsql 1 20 0 67536M 5788K sbwait 23 5:14 0=
.00% postgres
> >>>> 2035 pgsql 1 20 0 67536M 4892K sbwait 18 4:52 0=
.00%
> <postgres>
> >>>> 1852 pgsql 1 21 0 67536M 1230M semwai 7 4:47 0=
.00%
> postgres
> >>>> 13 root 3 -8 - 0K 48K - 28 4:46 0=
.00% geom
> >>>>
> >>>>
> >>> Another thing I've noticed is that this sysctl vm.stats counter is
> increasing
> >> fairly rapidly:
> >>> # sysctl vm.stats.vm.v_pdpages && sleep 1 && sysctl
> >> vm.stats.vm.v_pdpages
> >>> vm.stats.vm.v_pdpages: 3455264541
> >>> vm.stats.vm.v_pdpages: 3662158383
> >> I'm not sure what that tells us, because both the page daemon and the
> vm
> >> ("swap") daemon increment this counter.
> >>
> >>> Also, to demonstrate what kind of problems this seems to cause:
> >>> # time sleep 1
> >>>
> >>> real 0m18.288s
> >>> user 0m0.001s
> >>> sys 0m0.004s
> >> If you change the sysctl vm.swap_enabled to 0, how does your system
> >> behave?
> >>
> > Setting vm.swap_enabled to 0 made the problem clear up almost
> instantly. vmdaemon is back to 0.00% CPU usage and the system is
> responsive once again.
> >
> >
>=20
> I doubt that you need whole process swapping. The page daemon is
> probably sufficient. See how things go for a few days and let me know.
>=20
> There is still a bug here that needs diagnosing and fixing. So, I will
> likely send you a debugging patch in the near future, and ask you to
> reenable swapping under that patch.
>=20
If it helps at all - setting vm.swap_enabled=3D0 seems to fix the problem e=
ven without the aforementioned patch to vm_pageout.c.
Thanks again,
Steve
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