Re: Speed up Clog Access by increasing CLOG buffers

On 2016-03-31 15:07:22 +0530, Amit Kapila wrote:
> On Thu, Mar 31, 2016 at 4:39 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> >
> > On 2016-03-28 22:50:49 +0530, Amit Kapila wrote:
> > > On Fri, Sep 11, 2015 at 8:01 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> > > wrote:
> > > >
> >
> > Amit, could you run benchmarks on your bigger hardware? Both with
> > USE_CONTENT_LOCK commented out and in?
> >
>
> Yes.

Cool.

> > I think we should go for 1) and 2) unconditionally.

> Yes, that makes sense. On 20 min read-write pgbench --unlogged-tables
> benchmark, I see that with HEAD Tps is 36241 and with increase the clog
> buffers patch, Tps is 69340 at 128 client count (very good performance
> boost) which indicates that we should go ahead with 1) and 2) patches.

Especially considering the line count... I do wonder about going crazy
and increasing to 256 immediately. It otherwise seems likely that we'll
have the the same issue in a year. Could you perhaps run your test
against that as well?

> I think we should change comments on top of this function.

Yes, definitely.

> 0001-Improve-64bit-atomics-support
>
> +#if 0
> +#ifndef PG_HAVE_ATOMIC_READ_U64
> +#define PG_HAVE_ATOMIC_READ_U64
> +static inline uint64
>
> What the purpose of above #if 0? Other than that patch looks good to me.

I think I was investigating something. Other than that obviously there's
no point. Sorry for that.

Greetings,

Andres Freund