[DUG] [computing] Re: Memory mapped Files with no file

[Peter Ingham]

Memory mapped files with no mapping file (i.e.  file handle = 0)  use 
(parts of) the system swap (page) file.

If you have dynamically sized swap files, they can become very 
fragmented over time (and often are never defragmented).

You might want to check how fragmented the page file is, and also look 
at making the size of it static (this prevents any additional 
fragmentation).

Cheers

On 12/06/2013 3:01 p.m., Ross Levis wrote:
>
> Hi Rob,
>
> The sleep is in the separate thread, not main thread.
>
> I'm not sure if in memory mapped files can be paged to disk but will 
> investigate.
>
> Cheers,
>
> Ross.
>
> *From:*delphi-bounces at listserver.123.net.nz 
> [mailto:delphi-bounces at listserver.123.net.nz] *On Behalf Of *Robert Martin
> *Sent:* Wednesday, 12 June 2013 9:05 AM
> *To:* NZ Borland Developers Group - Delphi List
> *Subject:* Re: [DUG] Memory mapped Files with no file
>
> Hi
>
> Don't know anything about memory mapped files but two comments...
>
> 1.  Try it without the sleep().   If the sleep is in the main thread 
> it could cause you problems.
> 2.  Perhaps you are low on RAM and the in memory file is actually 
> having to be paged to disk!
>
> Hope that's of some use :)
> Rob
>
> On 12/06/2013 12:02 a.m., Ross Levis wrote:
>
>     I'm using a shared memory component in 2 apps which communicate
>     with each other.
>
>     I use a shared memory component which uses a memory mapped file
>     with no actual file on the hard drive.
>
>     I seem to be having a problem with communications between the 2
>     apps when the hard drive is busy.  It appears a change to the
>     shared memory is not showing up in the other app for over 20
>     seconds while the hard drive is busy.  Does that sound possible in
>     your opinion?
>
>     It doesn't make any sense to me but that's all I can come up with
>     currently. Communication appears to stop sometimes when a separate
>     thread starts up every 24 hours to load the contents of perhaps
>     3000 small files into RAM.  There is a sleep(15) between access of
>     each file to prevent the drive being too busy, but yet this issue
>     can occur sometimes during the 30 odd seconds this thread is running.
>
>     Cheers,
>     Ross.
>
>
>
>
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