CURRENT slow and shaky network stability

Sat Apr 2 23:15:00 UTC 2016

In message <20160402231955.41b05526.ohartman at zedat.fu-berlin.de>, "O. 
Hartmann"
 writes:
> --Sig_/eJJPtbrEuK1nN2zIpc7BmVr
> Content-Type: text/plain; charset=US-ASCII
> Content-Transfer-Encoding: quoted-printable
> 
> Am Sat, 2 Apr 2016 11:39:10 +0200
> "O. Hartmann" <ohartman at zedat.fu-berlin.de> schrieb:
> 
> > Am Sat, 2 Apr 2016 10:55:03 +0200
> > "O. Hartmann" <ohartman at zedat.fu-berlin.de> schrieb:
> >=20
> > > Am Sat, 02 Apr 2016 01:07:55 -0700
> > > Cy Schubert <Cy.Schubert at komquats.com> schrieb:
> > >  =20
> > > > In message <56F6C6B0.6010103 at protected-networks.net>, Michael Butler =
> writes:   =20
> > > > > -current is not great for interactive use at all. The strategy of
> > > > > pre-emptively dropping idle processes to swap is hurting .. big tim=
> e.     =20
> > > >=20
> > > > FreeBSD doesn't "preemptively" or arbitrarily push pages out to disk.=
>  LRU=20
> > > > doesn't do this.
> > > >    =20
> > > > >=20
> > > > > Compare inactive memory to swap in this example ..
> > > > >=20
> > > > > 110 processes: 1 running, 108 sleeping, 1 zombie
> > > > > CPU:  1.2% user,  0.0% nice,  4.3% system,  0.0% interrupt, 94.5% i=
> dle
> > > > > Mem: 474M Active, 1609M Inact, 764M Wired, 281M Buf, 119M Free
> > > > > Swap: 4096M Total, 917M Used, 3178M Free, 22% Inuse     =20
> > > >=20
> > > > To analyze this you need to capture vmstat output. You'll see the fre=
> e pool=20
> > > > dip below a threshold and pages go out to disk in response. If you ha=
> ve=20
> > > > daemons with small working sets, pages that are not part of the worki=
> ng=20
> > > > sets for daemons or applications will eventually be paged out. This i=
> s not=20
> > > > a bad thing. In your example above, the 281 MB of UFS buffers are mor=
> e=20
> > > > active than the 917 MB paged out. If it's paged out and never used ag=
> ain,=20
> > > > then it doesn't hurt. However the 281 MB of buffers saves you I/O. Th=
> e=20
> > > > inactive pages are part of your free pool that were active at one tim=
> e but=20
> > > > now are not. They may be reclaimed and if they are, you've just saved=
>  more=20
> > > > I/O.
> > > >=20
> > > > Top is a poor tool to analyze memory use. Vmstat is the better tool t=
> o help=20
> > > > understand memory use. Inactive memory isn't a bad thing per se. Moni=
> tor=20
> > > > page outs, scan rate and page reclaims.
> > > >=20
> > > >    =20
> > >=20
> > > I give up! Tried to check via ssh/vmstat what is going on. Last lines b=
> efore broken
> > > pipe:
> > >=20
> > > [...]
> > > procs  memory       page                    disks     faults         cpu
> > > r b w  avm   fre   flt  re  pi  po    fr   sr ad0 ad1   in    sy    cs =
> us sy id
> > > 22 0 22 5.8G  1.0G 46319   0   0   0 55721 1297   0   4  219 23907  540=
> 0 95  5  0
> > > 22 0 22 5.4G  1.3G 51733   0   0   0 72436 1162   0   0  108 40869  345=
> 9 93  7  0
> > > 15 0 22  12G  1.2G 54400   0  27   0 52188 1160   0  42  148 52192  436=
> 6 91  9  0
> > > 14 0 22  12G  1.0G 44954   0  37   0 37550 1179   0  39  141 86209  436=
> 8 88 12  0
> > > 26 0 22  12G  1.1G 60258   0  81   0 69459 1119   0  27  123 779569 704=
> 359 87 13  0
> > > 29 3 22  13G  774M 50576   0  68   0 32204 1304   0   2  102 507337 484=
> 861 93  7  0
> > > 27 0 22  13G  937M 47477   0  48   0 59458 1264   3   2  112 68131 4440=
> 7 95  5  0
> > > 36 0 22  13G  829M 83164   0   2   0 82575 1225   1   0  126 99366 3806=
> 0 89 11  0
> > > 35 0 22 6.2G  1.1G 98803   0  13   0 121375 1217   2   8  112 99371  49=
> 99 85 15  0
> > > 34 0 22  13G  723M 54436   0  20   0 36952 1276   0  17  153 29142  443=
> 1 95  5  0
> > > Fssh_packet_write_wait: Connection to 192.168.0.1 port 22: Broken pipe
> > >=20
> > >=20
> > > This makes this crap system completely unusable. The server (FreeBSD 11=
> .0-CURRENT #20
> > > r297503: Sat Apr  2 09:02:41 CEST 2016 amd64) in question did poudriere=
>  bulk job. I
> > > can not even determine what terminal goes down first - another one, muc=
> h more time
> > > idle than the one shwoing the "vmstat 5" output, is still alive!=20
> > >=20
> > > i consider this a serious bug and it is no benefit what happened since =
> this "fancy"
> > > update. :-( =20
> >=20
> > By the way - it might be of interest and some hint.
> >=20
> > One of my boxes is acting as server and gateway. It utilises NAT, IPFW, w=
> hen it is under
> > high load, as it was today, sometimes passing the network flow from ISP i=
> nto the network
> > for clients is extremely slow. I do not consider this the reason for coll=
> apsing ssh
> > sessions, since this incident happens also under no-load, but in the over=
> all-view onto
> > the problem, this could be a hint - I hope.=20
> 
> I just checked on one box, that "broke pipe" very quickly after I started p=
> oudriere,
> while it did well a couple of hours before until the pipe broke. It seems i=
> t's load
> dependend when the ssh session gets wrecked, but more important, after the =
> long-haul
> poudriere run, I rebooted the box and tried again with the mentioned broken=
>  pipe after a
> couple of minutes after poudriere ran. Then I left the box for several hour=
> s and logged
> in again and checked the swap. Although there was for hours no load or othe=
> r pressure,
> there were 31% of of swap used - still (box has 16 GB of RAM and is propell=
> ed by a XEON
> E3-1245 V2).
> 

31%! Is it *actively* paging or is the 31% previously paged out and no 
paging is *currently* being experienced? 31% of how swap space in total?

Also, what does ps aumx or ps aumxww say? Pipe it to head -40 or similar.

-- 
Cheers,
Cy Schubert <Cy.Schubert at komquats.com> or <Cy.Schubert at cschubert.com>
FreeBSD UNIX:  <cy at FreeBSD.org>   Web:  http://www.FreeBSD.org

	The need of the many outweighs the greed of the few.