Why does FASM use so much memory?

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revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20524
Location: In your JS exploiting you and your system

revolution 02 Sep 2009, 05:22

windwakr wrote:

For my test I used a brand new download of "fasm.exe" out of "flat assembler 1.68 for DOS". Wouldn't that fall under the category of "fasm for DOS and for Win32 console"? So, why did it only allocate 15MB?

DOS != Win32 console

02 Sep 2009, 05:22

windwakr

Joined: 30 Jun 2004
Posts: 827

windwakr 02 Sep 2009, 05:25

He said
"both fasm for DOS and for Win32 console use the amount based on what is available by default."
What is "fasm.exe" out of "flat assembler 1.68 for DOS" then?

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02 Sep 2009, 05:25

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20524
Location: In your JS exploiting you and your system

revolution 02 Sep 2009, 05:28

Your settings for the DOS emulator (NTVDM) will dictate how much memory is available to DOS programs.

Win32 console is a 32bit process and can directly query the API for memory availability.

02 Sep 2009, 05:28

windwakr

Joined: 30 Jun 2004
Posts: 827

windwakr 02 Sep 2009, 05:31

Ah, I see. Didn't know the DOS emulated programs didn't have access to all the memory.

Here's the output on the Win32 console one:

Code:

[BLAH] >fasm test.asm
flat assembler  version 1.68  (1110194 kilobytes memory)
1 passes, 8043 bytes.

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02 Sep 2009, 05:31

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 02 Sep 2009, 10:54

Quote:

Anyway, maybe it could be possible to just reserve the address space in Windows and catch the page fault exception in order to allocate new pages in the middle when needed? But I still doubt it would give any advantage, it would probably only decrease the performance and not help with anything.

Nice idea. If there was some serious issue with FASM eating too much memory, someone might welcome this as an extra option (command line extra switch). But I am not sure either if there is use for that.

02 Sep 2009, 10:54

Borsuc

Joined: 29 Dec 2005
Posts: 2465
Location: Bucharest, Romania

Borsuc 02 Sep 2009, 14:58

windwakr wrote:

Ah, I see. Didn't know the DOS emulated programs didn't have access to all the memory.

Here's the output on the Win32 console one:
Code:
[BLAH] >fasm test.asm
flat assembler  version 1.68  (1110194 kilobytes memory)
1 passes, 8043 bytes.
    

That means you have more than 1GB free space Wink

I had around 700MB free at the time, now it uses almost 2GB Laughing

Question: does this trash my cache that is in RAM?

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02 Sep 2009, 14:58

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