From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | mimo(at)interdata(dot)com(dot)pl (Michal Mosiewicz) |
Cc: | hackers(at)postgresql(dot)org |
Subject: | Re: [HACKERS] mmap and MAP_ANON |
Date: | 1998-05-14 04:35:11 |
Message-ID: | 199805140435.AAA08577@candle.pha.pa.us |
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Lists: | pgsql-hackers |
>
> Bruce Momjian wrote:
> >
> > Would people tell me what platforms do NOT support the MAP_ANON flag to
> > the mmap() system call? You should find it in the mmap() manual page.
> >
> > *BSD has it, but I am not sure of the others. I am researching cache
> > size issues and the use of mmap vs. SYSV shared memory.
>
> Well, I haven't noticed this discussion. However, I can't understand one
> thing:
>
> Why a lot of people investigate how to replace shared memory with
> mmapping anonymously but there is no discussion on replacing
> reads/writes with memory mapping of heap files.
>
> This way we would save not only on having better system cache
> utilisation but also we would have less memory copying. For me it seems
> like a more robust solution. I suggested it few months ago.
>
> If it's a bad idea, I wonder why?
> Are there any systems that cannot do mmaps at all?
mmap'ing a file is not necessary faster. I will post time timings soon
that show this is not the case.
--
Bruce Momjian | 830 Blythe Avenue
maillist(at)candle(dot)pha(dot)pa(dot)us | Drexel Hill, Pennsylvania 19026
+ If your life is a hard drive, | (610) 353-9879(w)
+ Christ can be your backup. | (610) 853-3000(h)
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