Re: [Boost-users] [Interprocess] Page default

Subject: Re: [Boost-users] [Interprocess] Page default
From: Kelly, Dan (Dan.Kelly_at_[hidden])
Date: 2013-07-24 19:41:30

To elaborate on Ion's remarks, ALL virtual memory in user space in windows is backed by the page file, and ALL file I/O is memory mapped, the only difference being virtual memory is backed by the page file rather than a specific named file in the file system. Your inter process memory is just as likely to be in physical memory as any other data. So most likely this is not the cause of your performance issue, unless memory is so tight that your entire process working set is continually thrashing.

Dan



-----Original Message-----
From: Ion Gaztañaga [igaztanaga_at_[hidden]<mailto:igaztanaga_at_[hidden]>]
Sent: Wednesday, July 24, 2013 06:48 PM Eastern Standard Time
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Interprocess] Page default


El 18/07/2013 14:45, Oodini escribió:
> Hello,
>
> I use Boost.Interprocess on Windows 2003 Server.
>
> I am experiencing performances troubles. I am trying to understand
> what happens, and arrived on Microsoft web pages.
>
> I seems that on Windows, shared memory is implemented only through
> mapped files, and that only a portion of the shared memory is
> physically in the RAM (this limited number of pages is called
> "working set").
>
> The Windows API provides some functions for this working set :
> http://msdn.microsoft.com/en-us/library/windows/desktop/cc441804%28v=vs.85%29.aspx

>
>  I would have liked Interprocess wraps the functions
> GetProcessMemoryInfo() and SetProcessWorkingSetSize(), so that the
> full shared memory is put in RAM.

Inteprocess can't do that because it's a portable library and POSIX
systems don't know what a working set is. You can perfectly call those
functions yourself as you don't need any internal Interprocess data to
call them.

Although shared memory is never guaranteed to be in RAM, you don't any
any guarantee with your "process memory" (if memory pressure is detected
the OS can swap you heap and/or executable pages to the swap file to
free some RAM for other processes).

Best,

Ion
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