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From pgsql-hackers-owner+M23388@postgresql.org Mon Jun 3 17:54:43 2002

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Message-ID: <0e0a01c20b49$26e90a00$22c30191@comm.mot.com>

From: "Igor Kovalenko" <Igor.Kovalenko@motorola.com>

To: "Bruce Momjian" <pgman@candle.pha.pa.us>

cc: "Tom Lane" <tgl@sss.pgh.pa.us>, "mlw" <markw@mohawksoft.com>,

"Marc G. Fournier" <scrappy@hub.org>, <pgsql-hackers@postgresql.org>

References: <200206030047.g530lZi21901@candle.pha.pa.us>

Subject: Re: [HACKERS] HEADS UP: Win32/OS2/BeOS native ports

Date: Mon, 3 Jun 2002 16:53:51 -0500

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Status: OR

That's what Apache does. Note, on most platforms MAP_ANON is equivalent to

mmmap-ing /dev/zero. Solaris for example does not provide MAP_ANON but using

fd=open(/dev/zero)

mmap(fd, ...)

close(fd)

works just fine.

----- Original Message -----

From: "Bruce Momjian" <pgman@candle.pha.pa.us>

To: "Igor Kovalenko" <Igor.Kovalenko@motorola.com>

Cc: "Tom Lane" <tgl@sss.pgh.pa.us>; "mlw" <markw@mohawksoft.com>; "Marc G.

Fournier" <scrappy@hub.org>; <pgsql-hackers@postgresql.org>

Sent: Sunday, June 02, 2002 7:47 PM

Subject: Re: [HACKERS] HEADS UP: Win32/OS2/BeOS native ports

> Igor Kovalenko wrote:

> > It does not have to be anonymous. POSIX also defines shm_open(same

arguments

> > as open) API which will create named object in whatever location

corresponds

> > to shared memory storage on that platform (object is then grown to

needed

> > size by ftruncate() and the fd is then passed to mmap). The object will

> > exist in name space and can be detected by subsequent calls to

shm_open()

> > with same name. It is not really different from doing open(), but more

> > portable (mmap() on regular files may not be supported).

>

> Actually, I think the best shared memory implemention would be

> MAP_ANON | MAP_SHARED mmap(), which could be called from the postmaster

> and passed to child processes.

>

> While all our platforms have mmap(), many don't have MAP_ANON, but those

> that do could use it. You need MAP_ANON to prevent the shared memory

> from being written to a disk file.

>

> --

> Bruce Momjian | http://candle.pha.pa.us

> pgman@candle.pha.pa.us | (610) 853-3000

> + If your life is a hard drive, | 830 Blythe Avenue

> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026

>

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