Re: Speed up Clog Access by increasing CLOG buffers

On Wed, Sep 14, 2016 at 12:55 AM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> 2. Results
> ./pgbench -c $threads -j $threads -T 10 -M prepared postgres -f script.sql
> scale factor: 300
> Clients   head(tps)        grouplock(tps)          granular(tps)
> -------      ---------               ----------                   -------
> 128        29367                 39326                    37421
> 180        29777                 37810                    36469
> 256        28523                 37418                    35882
>
>
> grouplock --> 1) Group mode to reduce CLOGControlLock contention
> granular  --> 2) Use granular locking model
>
> I will test with 3rd approach also, whenever I get time.
>
> 3. Summary:
> 1. I can see on head we are gaining almost ~30 % performance at higher
> client count (128 and beyond).
> 2. group lock is ~5% better compared to granular lock.

Sure, but you're testing at *really* high client counts here.  Almost
nobody is going to benefit from a 5% improvement at 256 clients.  You
need to test 64 clients and 32 clients and 16 clients and 8 clients
and see what happens there.  Those cases are a lot more likely than
these stratospheric client counts.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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