| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SP-GiST micro-optimizations |
| Date: | 2012-08-28 18:42:27 |
| Message-ID: | 6524.1346179347@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 28.08.2012 20:30, Tom Lane wrote:
>> Fascinating. I'd been of the opinion that modern compilers would inline
>> memset() for themselves and MemSet was probably not better than what the
>> compiler could do these days. What platform are you testing on?
> x64, gcc 4.7.1, running Debian.
> The assembly generated for the MemSet is:
> [ pretty darn tight ]
> while the corresponding memset code is:
> [ not so good ]
Seems like that's down to the CPU not doing "rep stosq" particularly
quickly, which might well be chip-specific.
Anyway, IIRC there are similar memsets for all the SPGiST opclass
invocation calls, so I guess you should switch them all not just these
two.
regards, tom lane
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