Horton

Re: LogwrtResult contended spinlock

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Jeff Davis <pgsql@j-davis.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Jaime Casanova <jcasanov@systemguards.com.ec>
Date: 2024-04-03T17:57:32Z
Lists: pgsql-hackers 
On 2024-Apr-03, Bharath Rupireddy wrote:

> On Wed, Apr 3, 2024 at 4:49 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> > So what I do in the attached 0001 is stop using the XLogwrtResult struct
> > in XLogCtl and replace it with separate Write and Flush values, and add
> > the macro XLogUpdateLocalLogwrtResult() that copies the values of Write
> > and Flush from the shared XLogCtl to the local variable given as macro
> > argument.  (I also added our idiomatic do {} while(0) to the macro
> > definition, for safety).  The new members are XLogCtl->logWriteResult
> > and XLogCtl->logFlushResult and as of 0001 are just XLogRecPtr, so
> > essentially identical semantics as the previous code.  No atomic access
> > yet!
> 
> +1.

> Also, I'm fine with renaming XLogUpdateLocalLogwrtResult() to
> RefreshXLogWriteResult().

Okay, I have pushed 0001 with the name change, will see about getting
the others in tomorrow.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/

Commits

  1. Remove bogus assertion in pg_atomic_monotonic_advance_u64

  2. Add XLogCtl->logInsertResult

  3. Operate XLogCtl->log{Write,Flush}Result with atomics

  4. Split XLogCtl->LogwrtResult into separate struct members

  5. Introduce atomic read/write functions with full barrier semantics.

  6. Reduce the number of GetFlushRecPtr() calls done by walsenders.

  7. Remove most volatile qualifiers from xlog.c