Re: Excessive context switching on SMP Xeons

Bill,

> I'd be thrilled to test it too, if for no other reason that to determine
> whether what I'm experiencing really is the "CS problem".

Hmmm ... Gavin's patch is built against 8.0, and any version of the patch
would require linux 2.6, probably 2.6.7 minimum. Can you test on that linux
version? Do you have the resources to back-port Gavin's patch?

> Fair enough. I never see nearly this much context switching on my dual
> Xeon boxes running dozens (sometimes hundreds) of concurrent apache
> processes, but I'll concede this could just be due to the more parallel
> nature of a bunch of independent apache workers.

Certainly could be. Heavy CSes only happen when you have a number of
long-running processes with contention for RAM in my experience. If Apache
is dispatching thing quickly enough, they'd never arise.

> Hence my desire for recommendations on alternate architectures ;-)

Well, you could certainly stay on Xeon if there's better support availability.
Just get off Dell *650's.

> Being a 24x7x365 shop, and these servers being mission critical, I
> require vendors that can offer 24x7 4-hour part replacement, like Dell
> or IBM. I haven't seen 4-way 64-bit boxes meeting that requirement for
> less than $20,000, and that's for a very minimally configured box. A
> suitably configured pair will likely end up costing $50,000 or more. I
> would like to avoid an unexpected expense of that size, unless there's
> no other good alternative. That said, I'm all ears for a cheaper
> alternative that meets my support and performance requirements.

No, you're going to pay through the nose for that support level. It's how
things work.

> tps = 369.717832 (including connections establishing)
> tps = 370.852058 (excluding connections establishing)

Doesn't seem too bad to me. Have anything to compare it to?

What's in your postgresql.conf?

--Josh