Re: NUMA packaging and patch

On 2014-07-01 11:01:04 +0200, Christoph Berg wrote:
> Re: Kevin Grittner 2014-06-09 <1402267501.41111.YahooMailNeo@web122304.mail.ne1.yahoo.com>
> > @@ -536,6 +539,24 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port,
> >           */
> >      }
> >  
> > +#ifdef USE_LIBNUMA
> > +    /*
> > +     * If this is not a private segment and we are using libnuma, make the
> > +     * large memory segment interleaved.
> > +     */
> > +    if (!makePrivate && numa_available())
> > +    {
> > +        void   *start;
> > +
> > +        if (AnonymousShmem == NULL)
> > +            start = memAddress;
> > +        else
> > +            start = AnonymousShmem;
> > +
> > +        numa_interleave_memory(start, size, numa_all_nodes_ptr);
> > +    }
> > +#endif
> 
> How much difference would it make if numactl --interleave=all was used
> instead of using numa_interleave_memory() on the shared memory
> segments? I guess that would make backend-local memory also
> interleaved, but it would avoid having a dependency on libnuma in the
> packages.

I've tested this a while ago, and it's rather painful if you have a OLAP
workload with lots of backend private memory.

> The numactl manpage even has this example:
> 
>     numactl --interleave=all bigdatabase arguments Run big
>     database with its memory interleaved on all CPUs.
> 
> It is probably better to have native support in the postmaster, though
> this could be mentioned as an alternative in the documentation.

I wonder if we shouldn't backpatch such a notice.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services