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Re: Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)
Date: 2013-01-11 19:33:29
Message-ID: 20130111193329.GE6049@awork2.anarazel.de (view raw, whole thread or download thread mbox)
Thread:
Lists: pgsql-hackers
On 2013-01-11 14:01:40 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > The attached patch:
>
> > * adds configure checks for __VA_ARGS__ and __builtin_unreachable
> >   support
> > * provides a pg_unreachable() macro that expands to
> >   __builtin_unreachable() or abort()
> > * changes #define elog ... into #define elog(elevel, ...) if varargs are
> >   available
>
> Seems like a good thing to do --- will review and commit.

Thanks.

I guess you will catch that anyway, but afaik msvc supports __VA_ARGS__
these days (since v2005 seemingly) and I didn't add HAVE__VA_ARGS to the
respective pg_config.h.win32

> > It does *not* combine elog_start and elog_finish into one function if
> > varargs are available although that brings a rather measurable
> > size/performance benefit.
>
> Since you've apparently already done the measurement: how much?
> It would be a bit tedious to support two different infrastructures for
> elog(), but if it's a big enough win maybe we should.

Imo its pretty definitely a big enough win. So big I have a hard time
believing it can be true without negative effects somewhere else.

Ontop of the patch youve replied to it saves somewhere around 80kb and
between 0.8 (-S -M prepared), 2% (-S -M simple) and 4% (own stuff) I had
lying around and it consistently gives 6%-7% in Pavel's testcase. With
todays HEAD, not with the one before your fix.

I attached the absolutely ugly and unready patch I used for testing.

Greetings,

Andres Freund

--
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Attachment: ugly-elog-fold.patch
Description: text/x-patch (2.1 KB)

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Subject: Re: Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)

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