Re: FW: REVIEW: Allow formatting in log_line_prefix
| От | David Rowley |
|---|---|
| Тема | Re: FW: REVIEW: Allow formatting in log_line_prefix |
| Дата | |
| Msg-id | CAApHDvq_LpTqXa826dBnHMxJG=yWFfr44Yf+BqtCDMqdjWMjQA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: FW: REVIEW: Allow formatting in log_line_prefix (Andres Freund <andres@2ndquadrant.com>) |
| Список | pgsql-hackers |
On Wed, Sep 25, 2013 at 6:25 AM, Andres Freund <andres@2ndquadrant.com> wrote:
On 2013-09-24 19:56:32 +0200, Andres Freund wrote:That's maybe misunderstandable, what I mean is to have an if (padding >
> On 2013-09-24 13:51:04 -0300, Alvaro Herrera wrote:
> > David Rowley escribió:
> >
> > > I do see a 15-18% slow down with the patched version, so perhaps I'll need
> > > to look to see if I can speed it up a bit, although I do feel this
> > > benchmark is not quite a normal workload.
> >
> > Ouch. That's certainly way too much. Is the compiler inlining
> > process_log_prefix_padding()? If not, does it do it if you add "inline"
> > to it? That might speed up things a bit. If that's not enough, maybe
> > you need some way to return to the original coding for the case where no
> > padding is set in front of each option.
>
> From a very short look without actually running it I'd guess the issue
> is all the $* things you're now passing to do appendStringInfo (which
> passes them off to vsnprintf).
> How does it look without that?
0) around the the changed appendStringInfo invocations and use the old
ones otherwise.
Yeah I had the same idea to try that next. I suspect that's where the slow down is rather than the processing of the padding. I'm thinking these small tweaks are going to make the code a bit ugly, but I agree about the 15-18% slowdown is a no go. The only other thing apart from checking if padding > 0 is to check if the char after the % is > '9', in that case it can't be formatting as we're only allowing '-' and '0' to '9'. Although I think that's a bit hackish, but perhaps it is acceptable if it helps narrow the performance gap.
More benchmarks to follow soon.
David
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
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