| From: | Jesper Krogh <jesper(at)krogh(dot)cc> |
|---|---|
| To: | James Cloos <cloos(at)jhcloos(dot)com> |
| Cc: | Glyn Astill <glynastill(at)yahoo(dot)co(dot)uk>, Steve Clark <sclark(at)netwolves(dot)com>, david(at)lang(dot)hm, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Linux: more cores = less concurrency. |
| Date: | 2011-04-12 05:17:54 |
| Message-ID: | 4DA3E082.5040903@krogh.cc |
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| Lists: | pgsql-performance |
On 2011-04-11 22:39, James Cloos wrote:
>>>>>> "GA" == Glyn Astill<glynastill(at)yahoo(dot)co(dot)uk> writes:
> GA> I was hoping someone had seen this sort of behaviour before,
> GA> and could offer some sort of explanation or advice.
>
> Jesper's reply is probably most on point as to the reason.
>
> I know that recent Opterons use some of their cache to better manage
> cache-coherency. I presum recent Xeons do so, too, but perhaps yours
> are not recent enough for that?
Better cache-coherence also benefits, but it does nothing to
the fact that remote DRAM fetches is way more expensive
than local ones. (Hard numbers to get excact nowadays).
--
Jesper
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