From: | Radosław Smogura <rsmogura(at)softperience(dot)eu> |
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To: | Florian Pflug <fgp(at)phlo(dot)org> |
Cc: | PG Hackers <pgsql-hackers(at)postgresql(dot)org>, "Markus Wanner" <markus(at)bluegap(dot)ch> |
Subject: | Re: POSIX question |
Date: | 2011-06-20 14:39:01 |
Message-ID: | 201106201639.02157.rsmogura@softperience.eu |
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Lists: | pgsql-hackers |
Florian Pflug <fgp(at)phlo(dot)org> Monday 20 of June 2011 16:16:58
> 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
This may be achived by many other things, like mmap /dev/null.
Regards,
Radek
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