| From: | Florian Pflug <fgp(at)phlo(dot)org> |
|---|---|
| To: | Radosław Smogura <rsmogura(at)softperience(dot)eu> |
| Cc: | PG Hackers <pgsql-hackers(at)postgresql(dot)org>, "Markus Wanner" <markus(at)bluegap(dot)ch> |
| Subject: | Re: POSIX question |
| Date: | 2011-06-20 14:16:58 |
| Message-ID: | A42AB4B6-851C-491E-A43D-3EC5436F8D00@phlo.org |
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| Lists: | pgsql-hackers |
On Jun20, 2011, at 15:27 , Radosław Smogura wrote:
> 1. mmap some large amount of anonymous virtual memory (this will be maximum size of shared memory).
> ...
> Point 1. will no eat memory, as memory allocation is delayed and in 64bit platforms you may reserve quite huge chunk of this, and in future it may be possible using mmap / munmap to concat chunks / defrag it etc.
I think this breaks with strict overcommit settings (i.e. vm.overcommit_memory = 2 on linux). To fix that, you'd need a way to tell the kernel (or glibc) to simply reserve a chunk of virtual address space for further user. Not sure if there's a API for that...
best regards,
Florian Pflug
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