application frequently map and unmap memory

application frequently map and unmap memory

[Yuxin Ren]

Hi all,

Are there any applications that stress the memory mapping and unmapping utility
(It frequently map and unmap memory)?

Thanks
Yuxin

Re: application frequently map and unmap memory

[Rich Felker]

On Mon, Aug 01, 2016 at 06:06:29PM -0400, Yuxin Ren wrote:
> Hi all,
> 
> Are there any applications that stress the memory mapping and unmapping utility
> (It frequently map and unmap memory)?

Are you looking for real-world applications with this type of load? Or
artificial stress tests? I would not expect to find many of the former
since these are costly operations and there are usually better ways to
do whatever is needed. The latter should be easy to write if needed,
though.

Rich

Re: application frequently map and unmap memory

[Yuxin Ren]

I am looking for real-world applications
I guess if some applications use large chunk of memory, map and unmap
are necessary.
I just am not aware which applications have such requirements.

Thanks..

On Tue, Aug 2, 2016 at 12:18 PM, Rich Felker <dalias@libc.org> wrote:
> On Mon, Aug 01, 2016 at 06:06:29PM -0400, Yuxin Ren wrote:
>> Hi all,
>>
>> Are there any applications that stress the memory mapping and unmapping utility
>> (It frequently map and unmap memory)?
>
> Are you looking for real-world applications with this type of load? Or
> artificial stress tests? I would not expect to find many of the former
> since these are costly operations and there are usually better ways to
> do whatever is needed. The latter should be easy to write if needed,
> though.
>
> Rich

Re: application frequently map and unmap memory

[John Levine]

In article <CAAKbDrdMVskT=Azgnu6DPUpAbJa_gToUcq-jjCvRKe7CJmJ22g@mail.gmail.com> you write:
>I am looking for real-world applications
>I guess if some applications use large chunk of memory, map and unmap
>are necessary.
>I just am not aware which applications have such requirements.

If you just want to use a large chunk of memory, malloc() and free()
work fine.  Memory mapping is for situtations where you need to share
data between applications, or you want to do something on a whole file
so it's more efficicient to map the file into memory than to use reads
and writes.

My version of grepcidr uses mmap so it can scan through whole files as
fast as possible.  It's like the usual grep utility but specialized to
look for IP addresses, typically in large log files.

http://www.taugh.com/grepcidr-2/

It uses a state machine to scan through each file which never backs up
by more than one character so its usage is map a file, scan through
the whole thing sequentially, unmap it, map in the next file, and so
forth.

R's,
John