Horton

Re: Speed up Clog Access by increasing CLOG buffers

Amit Kapila <amit.kapila16@gmail.com>

View thread View on postgr.es
From: Amit Kapila <amit.kapila16@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael.paquier@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-10T11:25:43Z
Lists: pgsql-hackers 
On Fri, Mar 10, 2017 at 11:51 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Amit Kapila <amit.kapila16@gmail.com> writes:
>> Just to let you know that I think I have figured out the reason of
>> failure.  If we run the regressions with attached patch, it will make
>> the regression tests fail consistently in same way.  The patch just
>> makes all transaction status updates to go via group clog update
>> mechanism.
>
> This does *not* give me a warm fuzzy feeling that this patch was
> ready to commit.  Or even that it was tested to the claimed degree.
>

I think this is more of an implementation detail missed by me.  We
have done quite some performance/stress testing with a different
number of savepoints, but this could have been caught only by having
Rollback to Savepoint followed by a commit.  I agree that we could
have devised some simple way (like the one I shared above) to test the
wide range of tests with this new mechanism earlier.  This is a
learning from here and I will try to be more cautious about such
things in future.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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.