Re: [Boost-users] Memory deallocation concerning boost::bind, boost::asio and shared_ptr

Subject: Re: [Boost-users] Memory deallocation concerning boost::bind, boost::asio and shared_ptr
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2016-04-29 02:40:28

On 28 Apr 2016 at 12:14, Norman wrote:

> Alright, i made an example, that shows my problem:
> 
> http://melpon.org/wandbox/permlink/S56tYueJySIHdsWO
> 
> Vinnie_win aka. Vinnie falco told me, that I might be looking at the wrong
> indicator for my memory use. But I thought the Resident Set Size is the
> value to look for, since I want to know how much memory my program is
> currently allocating.
> 
> Any help would still be really appriciated :-)

You appear to not understand how virtual memory and the system memory 
allocator works and interact with one another. Please read the papers 
from Denning et al from the 1970s. All major OSs use his design.

RSS is the *cache* of memory held by the system in RAM of your 
process' memory. It is entirely dependent on system load, how much 
caching your kernel chooses, and what the libraries your processes do 
internally.

It has little relevance to "how much memory my program is currently 
allocating".

The closest proxy to such a thing - which doesn't really exist on any 
major OS of the past thirty years - is probably the dirtied page 
count. And even there, the system memory allocator will intentionally 
cache a large quantity of memory it fetches from the OS, so just 
because you free() everything you malloc() doesn't mean any memory is 
released to the system.

If you really, really, really want to always free everything you 
malloc, use mmap() to allocate and munmap() to free, or even use 
sbrk(). Note that your program will run four orders of magntitude 
slower.

tl;dr; If this really bothers you, use a custom STL allocator. 
Otherwise so long as dirtied pages doesn't keep rising over time, 
it's not an issue and don't worry about it.

Niall

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