Horton

Re: Speed up Clog Access by increasing CLOG buffers

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Simon Riggs <simon@2ndquadrant.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2015-12-21T06:27:25Z
Lists: pgsql-hackers

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On Fri, Dec 18, 2015 at 9:58 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Fri, Dec 18, 2015 at 1:16 AM, Amit Kapila <amit.kapila16@gmail.com>
wrote:
>
> >> Some random comments:
> >>
> >> - TransactionGroupUpdateXidStatus could do just as well without
> >> add_proc_to_group.  You could just say if (group_no >= NUM_GROUPS)
> >> break; instead.  Also, I think you could combine the two if statements
> >> inside the loop.  if (nextidx != INVALID_PGPROCNO &&
> >> ProcGlobal->allProcs[nextidx].clogPage == proc->clogPage) break; or
> >> something like that.
> >>

Changed as per suggestion.

> >> - memberXid and memberXidstatus are terrible names.  Member of what?
> >
> > How about changing them to clogGroupMemberXid and
> > clogGroupMemberXidStatus?
>
> What we've currently got for group XID clearing for the ProcArray is
> clearXid, nextClearXidElem, and backendLatestXid.  We should try to
> make these things consistent.  Maybe rename those to
> procArrayGroupMember, procArrayGroupNext, procArrayGroupXid
>

Here procArrayGroupXid sounds like Xid at group level, how about
procArrayGroupMemberXid?
Find the patch with renamed variables for PGProc
(rename_pgproc_variables_v1.patch) attached with mail.

> and then
> start all of these identifiers with clogGroup as you propose.
>

I have changed them accordingly in the attached patch
(group_update_clog_v4.patch)  and addressed other comments given by
you.


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.