| From: | "ktm(at)rice(dot)edu" <ktm(at)rice(dot)edu> |
|---|---|
| To: | Florian Pflug <fgp(at)phlo(dot)org> |
| Cc: | George Barnett <gbarnett(at)atlassian(dot)com>, Bernd Helmle <mailings(at)oopsware(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Patch to improve reliability of postgresql on linux nfs |
| Date: | 2011-09-13 13:22:42 |
| Message-ID: | 20110913132242.GM14035@staff-mud-56-27.rice.edu |
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| Lists: | pgsql-hackers |
On Tue, Sep 13, 2011 at 03:02:57PM +0200, Florian Pflug wrote:
> On Sep13, 2011, at 14:58 , ktm(at)rice(dot)edu wrote:
> > It will be interesting to see if there are any performance ramifications to
> > this new write function.
>
> What would those be? For non-interruptible reads and writes, the overhead
> comes down to an additional function call (if we don't make pg_write_nointr
> inlined) and a few conditional jumps (which branch prediction should be
> able to take care of). These are bound to disappear in the noise compared
> to the cost of the actual syscall.
>
> best regards,
> Florian Pflug
>
That would be my expectation too. It is just always nice to benchmark changes,
just in case. I have had similar simple changes blow out a cache and have a
much greater impact on performance than might be expected from inspection. :)
Regards,
Ken
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