Horton

Re: Speed up Clog Access by increasing CLOG buffers

Jesper Pedersen <jesper.pedersen@redhat.com>

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From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2015-09-18T17:38:59Z
Lists: pgsql-hackers 
On 09/11/2015 10:31 AM, Amit Kapila wrote:
> Updated comments and the patch (increate_clog_bufs_v2.patch)
> containing the same is attached.
>

I have done various runs on an Intel Xeon 28C/56T w/ 256Gb mem and 2 x 
RAID10 SSD (data + xlog) with Min(64,).

Kept the shared_buffers=64GB and effective_cache_size=160GB settings 
across all runs, but did runs with both synchronous_commit on and off 
and different scale factors for pgbench.

The results are in flux for all client numbers within -2 to +2% 
depending on the latency average.

So no real conclusion from here other than the patch doesn't help/hurt 
performance on this setup, likely depends on further CLogControlLock 
related changes to see real benefit.

Best regards,
  Jesper

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.