Re: RE: [COMMITTERS] pgsql/src/backend/access/transam ( xact.c xlog.c)

* Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> [001116 08:59] wrote:
> [ Charset ISO-8859-1 unsupported, converting... ]
> > > > > Earlier, Vadim was talking about arranging to share fsyncs of the WAL
> > > > > log file across transactions (after writing your commit record to the
> > > > > log, sleep a few milliseconds to see if anyone else fsyncs before you
> > > > > do; if not, issue the fsync yourself). That would offer less-than-
> > > > > one-fsync-per-transaction performance without giving up any
> > > > > guarantees.
> > > > > If people feel a compulsion to have a tunable parameter, let 'em tune
> > > > > the length of the pre-fsync sleep ...
> > > >
> > > > Already implemented (without ability to tune this parameter -
> > > > xact.c:CommitDelay, - yet). Currently CommitDelay is 5, so
> > > > backend sleeps 1/200 sec before checking/forcing log fsync.
> > >
> > > But it returns _completed_ to the client before sleeping, right?
> >
> > No.
>
> Ewe, so we have this 1/200 second delay for every transaction. Seems
> bad to me.

I think as long as it becomes a tunable this isn't a bad idea at
all. Fixing it at 1/200 isn't so great because people not wrapping
large amounts of inserts/updates with transaction blocks will
suffer.

--
-Alfred Perlstein - [bright(at)wintelcom(dot)net|alfred(at)freebsd(dot)org]
"I have the heart of a child; I keep it in a jar on my desk."