Horton

Re: Speed up Clog Access by increasing CLOG buffers

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Jesper Pedersen <jesper.pedersen@redhat.com>, David Steele <david@pgmasters.net>, Robert Haas <robertmhaas@gmail.com>, Thom Brown <thom@linux.com>, Simon Riggs <simon@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-03-22T07:03:07Z
Lists: pgsql-hackers 
On Thu, Mar 17, 2016 at 11:39 AM, Amit Kapila <amit.kapila16@gmail.com>
wrote:

 I have reviewed the patch.. here are some review comments, I will continue
to review..

1.

+
+ /*
+  * Add the proc to list, if the clog page where we need to update the

+  */
+ if (nextidx != INVALID_PGPROCNO &&
+ ProcGlobal->allProcs[nextidx].clogGroupMemberPage !=
proc->clogGroupMemberPage)
+ return false;

Should we clear all these structure variable what we set above in case we
are not adding our self to group, I can see it will not have any problem
even if we don't clear them,
I think if we don't want to clear we can add some comment mentioning the
same.

+ proc->clogGroupMember = true;
+ proc->clogGroupMemberXid = xid;
+ proc->clogGroupMemberXidStatus = status;
+ proc->clogGroupMemberPage = pageno;
+ proc->clogGroupMemberLsn = lsn;


2.

Here we are updating in our own proc, I think we don't need atomic
operation here, we are not yet added to the list.

+ if (nextidx != INVALID_PGPROCNO &&
+ ProcGlobal->allProcs[nextidx].clogGroupMemberPage !=
proc->clogGroupMemberPage)
+ return false;
+
+ pg_atomic_write_u32(&proc->clogGroupNext, nextidx);


-- 
Regards,
Dilip Kumar
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.