Re: [HACKERS] kqueue

On 28/09/2018 14:19, Thomas Munro wrote:
> On Fri, Sep 28, 2018 at 11:09 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
>> On 2018-09-28 10:55:13 +1200, Thomas Munro wrote:
>>> Matteo Beccati reported a 5-10% performance drop on a
>>> low-end Celeron NetBSD box which we have no explanation for, and we
>>> have no reports from server-class machines on that OS -- so perhaps we
>>> (or the NetBSD port?) should consider building with WAIT_USE_POLL on
>>> NetBSD until someone can figure out what needs to be fixed there
>>> (possibly on the NetBSD side)?
>>
>> Yea, I'm not too worried about that. It'd be great to test that, but
>> otherwise I'm also ok to just plonk that into the template.
>
> Thanks for the review! Ok, if we don't get a better idea I'll put
> this in src/template/netbsd:
>
> CPPFLAGS="$CPPFLAGS -DWAIT_USE_POLL"

A quick test on a 8 vCPU / 4GB RAM virtual machine running a fresh
install of NetBSD 8.0 again shows that kqueue is consistently slower
running pgbench vs unpatched master on tcp-b like pgbench workloads:

~1200tps vs ~1400tps w/ 96 clients and threads, scale factor 10

while on select only benchmarks the difference is below the noise floor,
with both doing roughly the same ~30k tps.

Out of curiosity, I've installed FreBSD on an identically specced VM,
and the select benchmark was ~75k tps for kqueue vs ~90k tps on
unpatched master, so maybe there's something wrong I'm doing when
benchmarking. Could you please provide proper instructions?

Cheers
--
Matteo Beccati

Development & Consulting - http://www.beccati.com/