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Re: [Bulk] Re: [OCLUG-Tech] A view/snapshot of what is in RAM ??

  • Subject: Re: [Bulk] Re: [OCLUG-Tech] A view/snapshot of what is in RAM ??
  • From: Bart Trojanowski <bart [ at ] jukie [ dot ] net>
  • Date: Wed, 3 Oct 2007 12:14:24 -0400
* William Case <billlinux [ at ] rogers [ dot ] com> [071003 11:55]:
> > http://www.osdata.com/system/physical/memmap.htm
> 
> Thanks.  Shows layouts for DOS and MAC.  I assume that re: Bios Linux OS
> would be the same as DOS, because the code is stored before any OS
> begins ??

Linux only calls 3 BIOS services (if you don't use APM) and then forgets
BIOS ever existed.

> > ... but since the early nighties (when the above was everything you
> > needed to know) it's gotten worse.  Now USB, ACPI, ATA, VIDEO, and other
> > parts of the BIOS reserve various regions.
> > 
> > INT 0x15, service 0xE820, was added for OS software to get the layout of
> > usable memory on the system.  This will list about 5 regions reserved to
> > different parts of the BIOS.  It also lists the physical memory regions
> > that the OS can use for whatever it wants.
> > 
> 
> Write a small C program to get access to this table/layout -- I
> assume ??

You cannot access it once Linux is running.  But you could write a small
program under DOS to access it.  You could even run this DOS in
emulation (qemu, bochs, dosemu, etc) under Linux.

> > > first and last address of my memory,
> > > BIOS that has been written to memory,
> > > Kernel space,
> > > User space,
> > >   shell,
> > >   processes (running and sleeping),
> > 
> > The above is not how you want to look at things.  User space runs in
> > virtual memory, which is seldom contiguous in physical memory.  
> 
> Understood.  But nonetheless I had hoped there was some organized
> fashion by which it could be invisioned.

Pages used by the application are scattered throughout physical memory.

The only thing I have seen that comes close to visualizing application
memory usage is Matt Mackall's Pagemap tool.

        http://selenic.com/Screenshot-pagemap.png

I don't know how polished any of those tools are.

-Bart

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