Re: multithreaded dll - what is going on in std::_Lockit?
<alan.lemon@gmail.com> wrote in message
news:1174407741.847432.194310@b75g2000hsg.googlegroups.com...
On Mar 20, 9:05 am, "Scott McPhillips [MVP]" <org-dot-mvps-at-
scottmcp> wrote:
alan.le...@gmail.com wrote:
I am working in VS2005 and I have created a multithreaded dll. For
this
particular project I need my code to be as fast as possible so I have
been using a profiler to see where any bottle necks exist in my
project. I am using Compuware's community edition profiler and
interestingly a lot of the time that my project spends is in :
std::_Lockit::_Lockit(int)
std::_Lockit::~_Lockit()
RtlEnterCriticalSection
RtlLeaveCriticalSection
I have done some searching around, but I don't understand what these
objects/functions do and if I can do anything about it. Any help would
be greatly appreciated.
They provide interthread synchronization. If more than one thread is
trying to access the same data then they cause all but one of the
threads to stall or suspend until the shared resource is available for
exclusive access.
One significant such shared resource is the heap. If you have a lot of
memory allocation/delete/reallocation in multiple threads all these
accesses to the heap manager delay each other. Anything you can do to
reduce heap changes for very busy objects is likely to improve this.
--
Scott McPhillips [VC++ MVP]
In my particular application I am really not concerned with being
thread safe. Is there any way to get rid of these calls?
If you don't need to create an object from one thread and delete it on
another, then create a separate unsynchronized heap for each thread. You
can still pass objects back and forth, but you can only ever free the object
using the same heap (and therefore thread if you couple it like this) that
allocated it.
HeapCreate(HEAP_NO_SERIALIZE) is your ticket. You may want to store the
heap handle in thread local storage.
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