Constant load of 1 on a recent 12-STABLE

[Allan Jude]

On 2020-06-03 16:29, Gordon Bergling wrote:
> Hi Allan,
> 
> On Wed, Jun 03, 2020 at 03:13:47PM -0400, Allan Jude wrote:
>> On 2020-06-03 06:16, Gordon Bergling via freebsd-hackers wrote:
>>> since a while I am seeing a constant load of 1.00 on 12-STABLE,
>>> but all CPUs are shown as 100% idle in top.
>>>
>>> Has anyone an idea what could caused this?
>>>
>>> The load seems to be somewhat real, since the buildtimes on this
>>> machine for -CURRENT increased from about 2 hours to 3 hours.
>>>
>>> This a virtualized system running on Hyper-V, if that matters.
>>>
>>> Any hints are more then appreciated.
>>>
>>> Kind regards,
>>>
>>> Gordon
>>
>> Try running 'top -SP' and see if that shows a specific CPU being busy,
>> or a specific process using CPU time
> 
> Below is the output of 'top -SP'. The only relevant process / thread that is
> relatively constant consumes CPU time seams to be 'zfskern'.
> 
> -----------------------------------------------------------------------------
> last pid: 68549;  load averages:  1.10,  1.19,  1.16 up 0+14:59:45  22:17:24
> 67 processes:  2 running, 64 sleeping, 1 waiting
> CPU 0:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
> CPU 1:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
> CPU 2:  0.0% user,  0.0% nice,  0.4% system,  0.0% interrupt, 99.6% idle
> CPU 3:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
> Mem: 108M Active, 4160M Inact, 33M Laundry, 3196M Wired, 444M Free
> ARC: 1858M Total, 855M MFU, 138M MRU, 96K Anon, 24M Header, 840M Other
>      461M Compressed, 1039M Uncompressed, 2.25:1 Ratio
> Swap: 2048M Total, 2048M Free
> 
>   PID USERNAME    THR PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
>    11 root          4 155 ki31     0B    64K RUN      0  47.3H 386.10% idle
>     8 root         65  -8    -     0B  1040K t->zth   0 115:39  12.61% zfskern
> -------------------------------------------------------------------------------
> 
> The only key performance indicator that is relatively high IMHO, for a 
> non-busy system, are the context switches, that vmstat has reported.
> 
> -------------------------------------------------------------------------------
> procs  memory       page                    disks     faults         cpu
> r b w  avm   fre   flt  re  pi  po    fr   sr da0 da1   in    sy    cs us sy id
> 0 0 0 514G  444M  7877   2   7   0  9595  171   0   0    0  4347 43322 17  2 81
> 0 0 0 514G  444M     1   0   0   0     0   44   0   0    0   121 40876  0  0 100
> 0 0 0 514G  444M     0   0   0   0     0   40   0   0    0   133 42520  0  0 100
> 0 0 0 514G  444M     0   0   0   0     0   40   0   0    0   120 43830  0  0 100
> 0 0 0 514G  444M     0   0   0   0     0   40   0   0    0   132 42917  0  0 100
> --------------------------------------------------------------------------------
> 
> Any other ideas what could generate that load?
> 
> Best regards,
> 
> Gordon
> 

I agree that load average looks out of place here when you look at the %
cpu idle, but I wonder if it is caused by a lot of short lived processes
or threads.

How quickly is the 'last pid' number going up?

You might also look at `zpool iostat 1` or `gstat -p` to see how busy
your disks are

-- 
Allan Jude

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 834 bytes
Desc: OpenPGP digital signature
URL: <http://lists.freebsd.org/pipermail/freebsd-hackers/attachments/20200603/cc711e9c/attachment.sig>