Re: OpenBSD 6.4 only using 1 core

Mon, 18 Feb 2019 14:15:56 -0800 


> On Feb 18, 2019, at 2:57 PM, G Douglas Davidson via Unbound-users 
> <[email protected]> wrote:
> 
> OpenBSD 6.4 and the included Unbound 1.8.1.  Intel NUC with 2 real CPUS and 2 
> Virtual.  Some sysctl stuff:
> 
>       hw.ncpu=4
>       hw.ncpufound=4
>       hw.ncpuonline=2
>       hw.smt=0
> 
> “top” shows four cpus with work distributed to only two of them.  “ps” and 
> the statistics emitted by Unbound show only one CPU working.
> 
> ps output:
> 
>       87709 ??  Is      0:00.02 unbound -c /var/unbound/etc/unbound.conf
>       86298 ??  S       1:49.24 unbound -c /var/unbound/etc/unbound.conf
> 
> unbound statistics (every hour):
> 
>> Feb 18 13:14:02 unbound1 unbound: [87709:0] info: server stats for thread 0: 
>> 0 queries, 0 answers from cache, 0 recursions, 0 prefetch, 0 rejected by ip 
>> ratelimiting
>> Feb 18 13:14:02 unbound1 unbound: [87709:0] info: server stats for thread 0: 
>> requestlist max 0 avg 0 exceeded 0 jostled 0
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: server stats for thread 1: 
>> 47870 queries, 18749 answers from cache, 29121 recursions, 0 prefetch, 0 
>> rejected by ip ratelimiting
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: server stats for thread 1: 
>> requestlist max 46 avg 5.96944 exceeded 0 jostled 0
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: average recursion 
>> processing time 0.888912 sec
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: histogram of recursion 
>> processing times
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: [25%]=0.0276987 
>> median[50%]=0.0609112 [75%]=0.128225
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info: lower(secs) upper(secs) 
>> recursions
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000000    0.000001 
>> 2779
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000008    0.000016 7
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000064    0.000128 1
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000128    0.000256 5
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000256    0.000512 25
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.000512    0.001024 197
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.001024    0.002048 69
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.002048    0.004096 52
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.004096    0.008192 103
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.008192    0.016384 222
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.016384    0.032768 
>> 5530
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.032768    0.065536 
>> 6483
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.065536    0.131072 
>> 6653
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.131072    0.262144 
>> 4023
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.262144    0.524288 
>> 1786
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    0.524288    1.000000 604
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    1.000000    2.000000 224
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    2.000000    4.000000 72
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    4.000000    8.000000 64
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:    8.000000   16.000000 53
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:   16.000000   32.000000 52
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:   32.000000   64.000000 49
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:   64.000000  128.000000 4
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:  128.000000  256.000000 30
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:  256.000000  512.000000 23
>> Feb 18 14:14:02 unbound1 unbound: [86298:1] info:  512.000000 1024.000000 6
>> Feb 18 14:14:02 unbound1 unbound: [87709:0] info: server stats for thread 0: 
>> 0 queries, 0 answers from cache, 0 recursions, 0 prefetch, 0 rejected by ip 
>> ratelimiting
>> Feb 18 14:14:02 unbound1 unbound: [87709:0] info: server stats for thread 0: 
>> requestlist max 0 avg 0 exceeded 0 jostled 0
> 
> 
> unbound.conf:
> 
>>        num-threads: 2
> 
> No other tweaks make to unbound.conf.  Version is as distributed under 
> OpenBSD 6.4.  Unbound works find under OpenBSD 6.2 on a cpu with 2 real cores 
> and no virtual.
> 
> 
> I’m thinking that this issue may have something to do with the way OpenBSD is 
> reporting available CPUs.  I’m going to turn hyperthreading off at the BIOS 
> level at some point (when I can.)  I am wondering if anyone has any 
> experience with this.  Where “this” is OpenBSD and Unbound with hw.smt=0 and 
> Unbound apparently not using more than one thread.
> 
> Thanks for any feedback!
> 
> —doug
> 
> --
> G Douglas Davidson
> [email protected]
> 
> 
> 

It appears that there is something in the logic of listen_dnsport.c that is 
attempting to use SO_REUSEPORT_LB that is causing OpenBSD to end up only using 
a single thread.  When I add this option to the unbound.conf:

        so-reuseport: no

I get utilization on both threads, but it is very unbalanced.  Still maybe a 
step in the right direction.

> unbound1# ps -ax | grep unbound
> 30490 ??  Ss      0:02.21 unbound -c /var/unbound/etc/unbound.conf
> 42777 ??  S       0:00.47 unbound -c /var/unbound/etc/unbound.conf

and

> Feb 18 17:04:20 unbound1 unbound: [30490:0] info: server stats for thread 0: 
> 361 queries, 192 answers from cache, 169 recursions, 0 prefetch, 0 rejected 
> by ip ratelimiting
> Feb 18 17:05:20 unbound1 unbound: [42777:1] info: server stats for thread 1: 
> 25 queries, 1 answers from cache, 24 recursions, 0 prefetch, 0 rejected by ip 
> ratelimiting


I’m not attempting to find an approach specific to OpenBSD that provides better 
utilization of each real core.

—doug

--
G Douglas Davidson
[email protected]

























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