Date: Wed, 10 Oct 2001 11:03:58 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: "Andrew L. Neporada" <andrew@nas.dgap.mipt.ru> Cc: Maxime Henrion <mux@qualys.com>, Dwayne <Dwayne.MacKinnon@xwave.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: Memory allocation question Message-ID: <200110101803.f9AI3w320703@earth.backplane.com> References: <Pine.BSF.4.21.0110101914280.51319-100000@nas.dgap.mipt.ru>
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:On Tue, 2 Oct 2001, Matt Dillon wrote:
:
:>
:> :
:> :Dwayne wrote:
:> :> I'm creating an app where I want to use memory to store data so I
:> :> can get at it quickly. The problem is, I can't afford the delays that
:> :> would occur if the memory gets swapped out. Is there any way in FreeBSD
:> :> to allocate memory so that the VM system won't swap it out?
:> :>
:> :I think mlock(2) is what you want.
:> :
:> :Maxime Henrion
:> :--
:> :Don't be fooled by cheap finnish imitations ; BSD is the One True Code
:>
:> Don't use mlock().
:
:Could you please explain that. Thanks.
mlock() can only be used by root, and it isn't really all that portable
an interface. It cannot guarentee that the memory will actually be
locked into core.
:>
:> Use SysV Shared memory segments. If you tell the kernel to use
:> physical ram for SysV shared memory (kern.ipc.shm_use_phys=1)
:> then any shm segments you allocate (see manual pages for
:> shmctl, shmget, and shmat) will reside in unswappable shared memory.
:>
:> -Matt
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