From: | "Gran Thyni" <goran(at)bildbasen(dot)se> |
---|---|
To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | PostgreSQL-development <hackers(at)postgreSQL(dot)org> |
Subject: | Re: [HACKERS] mmap and MAP_ANON |
Date: | 1998-05-11 14:08:58 |
Message-ID: | 3557067A.5D550A31@bildbasen.se |
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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.
SVR4 (at least older ones) does not support MMAP_ANON,
but the recommended in W. Richards Stevens'
"Advanced programming in the Unix environment" (aka the Bible part 2)
is to use /dev/zero.
This should be configurable with autoconf:
<PSEUDO CODE>
if (exists MAP_ANON) use it; else use /dev/zero
------------
flags = MAP_SHARED;
#ifdef HAS_MMAP_ANON
fd = -1;
flags |= MAP_ANON;
#else
fd = open('/dev/zero, O_RDWR);
#endif
area = mmap(0, size, PROT_READ|PROT_WRITE, flags, fd, 0);
</PSEUDO CODE>
regards,
--
---------------------------------------------
Göran Thyni, sysadm, JMS Bildbasen, Kiruna
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