Re: SYSV shared memory vs mmap performance

On Sat, Jan 26, 2013 at 7:00 AM, Francois Tigeot <ftigeot(at)wolfpond(dot)org> wrote:
> On Fri, Jan 25, 2013 at 05:55:19PM -0500, Robert Haas wrote:
>> On Fri, Jan 25, 2013 at 9:38 AM, Francois Tigeot <ftigeot(at)wolfpond(dot)org> wrote:
>> >
>> > Some links with more details about improvements and final results:
>> > http://www.shiningsilence.com/dbsdlog/2012/09/19/10403.html
>> > http://www.shiningsilence.com/dbsdlog/2012/10/11/10544.html
>> > http://www.dragonflybsd.org/performance/
>>
>> Well, that looks pretty cool. Is there anything we can sensibly do to
>> recover the lost performance on FreeBSD and NetBSD?
>
> Apart from reintroducing SYSV shm usage, I don't think the Postgres team
> can do much about it. Mmap really needs kernel work to perform well.
>
> Some FreeBSD people are looking into the issue and have started to run
> benchmarks of their own to find out what needs to be fixed; I guess they
> will adapt in time.
>
> I'm less optimistic on the NetBSD front: even though I reported major
> show-stopper bugs (system died under load and was unable to complete
> a pgbench run), no one seemed to care.

Hrm. I was hoping that you were going to say "yeah, just pass the
MAP_DONT_BE_STUPID flag, and it'll work great".

Frankly, if the NetBSD developers don't think it's important to make
the test case not crash the system, then I'm not sure there's much
point is us caring about whether the test case performs well. :-(

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company