[Bug libc/11261] malloc uses excessive memory for multi-threaded applications

["neleai at seznam dot cz" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=11261

--- Comment #18 from Ondrej Bilka <neleai at seznam dot cz> ---
On Thu, Dec 12, 2013 at 03:31:58AM +0000, siddhesh at redhat dot com wrote:
> https://sourceware.org/bugzilla/show_bug.cgi?id=11261
> 
> Siddhesh Poyarekar <siddhesh at redhat dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |siddhesh at redhat dot com
> 
> --- Comment #17 from Siddhesh Poyarekar <siddhesh at redhat dot com> ---
> (In reply to Ondrej Bilka from comment #16)
> > > Therefore the solution to a program with lots of threads is to limit the arenas > as a trade-off for memory.
> > 
> > That is a bandaid not a solution. Still there is no memory returned to
> > system when one first does allocations and then allocates auxiliary memory
> > like
> 
> You have not understood the bug report.
>
When you read discussion more carefully there are following posts where
this problem is mentioned:


Ulrich Drepper:

 You don't understand the difference between address space and allocated
 memory.

Rich Testardi:

Actually, I totally understand the difference and that is why I mentioned the 
fragmentation of memory...  When each arena has just a few straggling 
allocations, the maximum *committed* RAM required for the program's *working 
set* using the thread-preferred arena model is, in fact, N times that required 
for a traditional model, where N is the number of threads.  This shows up in 
real-world thrashing that could actually be avoided.  Basically, if the 
program is doing small allocations, a small percentage of stragglers can pin 
the entire allocated space -- and the allocated space is, in fact, much larger 
than it needs to be (and larger than it is in other OS's).  But thank you for

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