Re: How to find out which pages were copied-on-write?

[Michael Clark <michael@metaparadigm.com>]

On 07/13/04 01:21, Lutz Vieweg wrote:
> Michael Clark wrote:
> 
>> HPAs library LPSM sounds like what you're looking for.
>>
>> http://freshmeat.net/projects/lpsm/
>>
>> Or you can do what you want the hard way using mprotect and a SEGV 
>> handler.
> 
> 
> Certainly a valid idea to consider - doing all those things in 
> userspace... so
> thanks for the hint!
> 
> But wouldn't that introduce a significant overhead and undermine all of the
> nice advantages the kernel might have in scheduling I/O operations?

Not really. Plain read/write IO is generally faster than mmap IO anyway.
You don't use mmap for speed but rather for convenience.

> However, I shall really consider and profile the mprotect/sighandler 
> approach...
> 
> Regards,
> 
> Lutz Vieweg
> 
> PS: I'm using my own allocator already, so using the C-library 
> implementation
>     wouldn't gain me much...

This wasn't why I suggested it. It's has the commit semantics
on memory mapped files that you were asking about (the allocator
is optional I believe).

~mc