Re: [HACKERS] kqueue

Hi Thomas,

On 01/10/2018 01:09, Thomas Munro wrote:
> I don't know why the existence of the kqueue should make recvfrom()
> slower on the pgbench side.  That's probably something to look into
> off-line with some FreeBSD guru help.  Degraded performance for
> clients on the same machine does seem to be a show stopper for this
> patch for now.  Thanks for testing!

Glad to be helpful!

I've tried running pgbench from a separate VM and in fact kqueue 
consistently takes the lead with 5-10% more tps on select/prepared 
pgbench on NetBSD too.

What I have observed is that sys cpu usage is ~65% (35% idle) with 
kqueue, while unpatched master averages at 55% (45% idle): relatively 
speaking that's almost 25% less idle cpu available for a local pgbench 
to do its own stuff.

Running pgbench locally shows an average 47% usr / 53% sys cpu 
distribution w/ kqueue vs more like 50-50 w/ vanilla, so I'm inclined to 
think that's the reason why we see a performance drop instead. Thoguhts?


Cheers
-- 
Matteo Beccati

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