On Thu, 20 Oct 2005 23:03:47 +0100 Simon Riggs <[EMAIL PROTECTED]> wrote:
> On Wed, 2005-10-19 at 14:07 -0700, Mark Wong wrote: > > > > > > This isn't exactly elegant coding, but it provides a useful improvement > > > on an 8-way SMP box when run on 8.0 base. OK, lets be brutal: this looks > > > pretty darn stupid. But it does follow the CPU optimization handbook > > > advice and I did see a noticeable improvement in performance and a > > > reduction in context switching. > > > > I'm not in a position to try this again now on 8.1beta, but I'd welcome > > > a performance test result from anybody that is. I'll supply a patch > > > against 8.1beta for anyone wanting to test this. > > > > Ok, I've produce a few results on a 4 way (8 core) POWER 5 system, which > > I've just set up and probably needs a bit of tuning. I don't see much > > difference but I'm wondering if the cacheline sizes are dramatically > > different from Intel/AMD processors. I still need to take a closer look > > to make sure I haven't grossly mistuned anything, but I'll let everyone > > take a look: > > Well, the Power 5 architecture probably has the lowest overall memory > delay you can get currently so in some ways that would negate the > effects of the patch. (Cacheline is still 128 bytes, AFAICS). But it's > clear the patch isn't significantly better (like it was with 8.0 when we > tried this on the 8-way Itanium in Feb). > > > cvs 20051013 > > http://www.testing.osdl.org/projects/dbt2dev/results/dev4-014/19/ > > 2501 notpm > > > > cvs 20051013 w/ lw.patch > > http://www.testing.osdl.org/projects/dbt2dev/results/dev4-014/20/ > > 2519 notpm > > Could you re-run with wal_buffers = 32 ? (Without patch) Thanks Ok, sorry for the delay. I've bumped up the wal_buffers to 2048 and redid the disk layout. Here's where I'm at now: cvs 20051013 http://www.testing.osdl.org/projects/dbt2dev/results/dev4-014/40/ 3257 notpm cvs 20051013 w/ lw.patch http://www.testing.osdl.org/projects/dbt2dev/results/dev4-014/42/ 3285 notpm Still not much of a difference with the patch. A quick glance over the iostat data suggests I'm still not i/o bound, but the i/o wait is rather high according to vmstat. Will try to see if there's anything else obvious to get the load up higher. Mark ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
