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Re: A patch for xlog.c

From: Matthew Kirkwood <matthew(at)hairy(dot)beasts(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: A patch for xlog.c
Date: 2001-02-24 23:45:31
Message-ID: Pine.LNX.4.10.10102242301310.17152-100000@sphinx.mythic-beasts.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
On Sat, 24 Feb 2001, Tom Lane wrote:

> > Forgive me if I posted it to the wrong place -- I was far from
> > proposing this for inclusion.
>
> Diffs posted to pgsql-patches are generally considered to be requests
> for application of a patch.  If this is only an experiment it had best
> be clearly labeled as such.

OK.  Is there are better place for discussion of such?

> > It is but a small step on the way to my plan of mmap()ifying all
> > of the WAL stuff (which may also prove a waste of effort).
>
> Very probably.  What are your grounds for thinking that's a good idea?
> I can't see any reason to think that mmap is more efficient than write
> for simple sequential writes, which is what we need to do.

Potential pros:

a. msync(MS_ASYNC) seems to be exactly
b. Potential to reduce contention
c. Removing syscalls is rarely a bad thing
d. Fewer copies, better cache behaviour

Potential cons:

a. Portability
b. A bad pointer can cause a scribble on the log

Matthew.


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