Horton

Re: Speed up Clog Access by increasing CLOG buffers

Robert Haas <robertmhaas@gmail.com>

View thread View on postgr.es
From: Robert Haas <robertmhaas@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-09-14T15:29:48Z
Lists: pgsql-hackers 
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
The Enterprise PostgreSQL Company

Commits

  1. Use group updates when setting transaction status in clog.

  2. Improve 64bit atomics support.

  3. Add ProcArrayGroupUpdate wait event.

  4. Make the different Unix-y semaphore implementations ABI-compatible.

  5. Fix broken ALTER INDEX documentation

  6. Code and docs review for commit 3187d6de0e5a9e805b27c48437897e8c39071d45.

  7. Partition the freelist for shared dynahash tables.

  8. Correct StartupSUBTRANS for page wraparound

  9. Make idle backends exit if the postmaster dies.

  10. contrib/sslinfo: add ssl_extension_info SRF

  11. Reduce ProcArrayLock contention by removing backends in batches.

  12. Fix `make installcheck` for serializable transactions.

  13. Lockless StrategyGetBuffer clock sweep hot path.

  14. Reduce sinval synchronization overhead.