| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | Hannu Krosing <hannu(at)krosing(dot)net> |
| Cc: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Free Space Map data structure |
| Date: | 2008-04-10 12:05:31 |
| Message-ID: | 47FE028B.7040802@enterprisedb.com |
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| Thread: | |
| Lists: | pgsql-hackers |
Hannu Krosing wrote:
> On Wed, 2008-04-09 at 21:09 +0300, Heikki Linnakangas wrote:
>> Hannu Krosing wrote:
>>> Saving 1 byte is an atomic op
>> Unfortunately, it's not. Most if not all modern CPUs will perform one
>> byte modification as "load word" + "modify word" + "save word".
>
> Hmm, maybe we I should change my design to modify page free info and its
> parent together ?
>
> or what is word ? 2 bytes ? 4 bytes ? even 8 bytes ?
It depends on architecture, I believe it's 4 bytes on 32-bit
architectures and 8 bytes on 64-bit ones, typically. But we have to work
on all of them.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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