Re: Lock memory ?

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From: Doug G (nospam_at_frcnospam.com)
Date: 02/19/04 

Date: Thu, 19 Feb 2004 13:43:33 -0500

(c) Good call. I suspect that VirtualLock might lock pages into the
process's working set, but of course that doesn't keep the working set
itself from being swapped out. The author of that documentation might have
missed the distinction between paging and swapping, assuming that the NT
kernel makes that distinction (which it probably does, or at least did at
one time, having been based on VMS).

  Doug G

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:ecs8301989132n84h0ic3n6l1t3c99r5tt@4ax.com...
> Yes. But you won't like the answer, and you almost certainly don't want to
do it.
>
> (a) There is far less memory than hard disk space. Disk space is cheap and
these days it
> can be thought of as nearly unlimited. Memory is expensive and extremely
limited.
>
> (b) Locking a big buffer in memory will screw up your entire system
performance.
>
> (c) If anyone tells you VirtualLock will work, they are wrong. The
documentation lies.
>
> (d) You can write a device driver that does it. You do not want to write a
device driver.
> There is an example of a Windows NT 4.0 driver that does this in our book
(Dekker &
> Newcomer, Writing WIndows NT Device Drivers) but it is a legacy driver.
You will need to
> write a plug-and-play power-managed driver, otherwise using the driver
disables all power
> management on the motherboard. PnP/PM drivers are tedious to write. Very
tedious. You can
> find prototypes on the DDK source tree, but this is not a topic you want
to tackle unless
> you really understand what you are doing.
>
> So what problem do you think this approach is going to solve? Saving disk
space? If so,
> you would be wasting your time. Improving performance? Maybe, for one
program, up to the
> point where you have consumed all the permissible kernel memory. Of
course, everything
> else goes to pieces in terms of performance, including the file system,
but your one
> program would run a little bit faster.
>
> Until you tell us what the problem is, asking us how to implement a
solution to an
> undefined problem is not really productive. I would say with a fair degree
of confidence
> that whatever the problem is, locking pages into physical memory is almost
certainly the
> wrong solution (I know of two instances where it makes sense, but I'll let
you define the
> problem space. It is almost certainly neither of the highly-esoteric
instances I know of).
> joe
>
> On Wed, 18 Feb 2004 19:15:47 +0100, "Erik" <saruman@pandora.be> wrote:
>
> >Is it possible to allocate a buffer in physical memory,
> >or lock the allocated memory, so, that it won't use hard disk space ?
> >
> >thx
> >
>
> Joseph M. Newcomer [MVP]
> email: newcomer@flounder.com
> Web: http://www.flounder.com
> MVP Tips: http://www.flounder.com/mvp_tips.htm

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