Hi all,
I know the standard doesn't care about threads (wrongly :-)
But in current compilers implementation, is the "list" which holds count
of the occupied and free heap addresses SHARED among various threads or not?
I don't know if I was clear:
Case1: the list which holds count of what is free and what is occupied
is SHARED among all the threads. In this case each
malloc/new/free/delete needs to acquire a mutex.
Case2: list (almost) thread local: no need for mutexes inside the
malloc/new/free/delete implementations , for most calls. So concurrent
access to malloc/new is fast
In this latter case of course there should be some heap address ranges
which are reserved for use by thread1, some are reserved for thread2...
so they don't usually conflict. If some thread fills up its address
range with mallocs, then it has to take a mutex and rearrange the
address ranges dedicated to the various threads so that it can get some
more heap range for the next mallocs...
I need to know the answer to evaluate if for fast
allocations/deallocations it should be wise to use something like an
allocator pool.
Oh another question: are distinct allocator functions for the various
classes automatically generated? It would seem wise to me to divide the
heap (or the section of the heap dedicated to one thread) in address
ranges, and each address range should be used for one class only. In
this way the allocation for various objects of the same type would be
contiguous and the memory would never be fragmented. Of course if one
class finishes its heap range, a reassignment of the heap ranges with
the other objects would have to be made.
TIA
14  5473 
John Doe wrote: Hi all,
I know the standard doesn't care about threads
So you know you're off-topic here.
(wrongly :-)
Depends on the view.
But in current compilers implementation, is the "list" which holds
count of the occupied and free heap addresses SHARED among various
threads or not?
Depends on the implementation, but I guess it is in most
implementations .
I don't know if I was clear:
Case1: the list which holds count of what is free and what is occupied
is SHARED among all the threads. In this case each
malloc/new/free/delete needs to acquire a mutex.
Or use one of the various other synchronization techniques, of which
some are in this case a lot better (more efficient) than mutexes.
Case2: list (almost) thread local: no need for mutexes inside the
malloc/new/free/delete implementations , for most calls. So concurrent
access to malloc/new is fast
In this latter case of course there should be some heap address ranges
which are reserved for use by thread1, some are reserved for
thread2... so they don't usually conflict. If some thread fills up its
address range with mallocs, then it has to take a mutex and rearrange
the address ranges dedicated to the various threads so that it can get
some more heap range for the next mallocs...
How could it rearrange the address space if there is already something
in it?
I need to know the answer to evaluate if for fast
allocations/deallocations it should be wise to use something like an
allocator pool.
There are quite a lot of malloc implemenations out there, and there may
be some that are quite efficient in multithreading environments. Just
google for them.
Oh another question: are distinct allocator functions for the various
classes automatically generated? It would seem wise to me to divide
the heap (or the section of the heap dedicated to one thread) in
address ranges, and each address range should be used for one class
only. In this way the allocation for various objects of the same type
would be contiguous and the memory would never be fragmented. Of
course if one class finishes its heap range, a reassignment of the
heap ranges with the other objects would have to be made.
Again, I wonder how you can reassign memory that is already in use.
>>Hi all, I know the standard doesn't care about threads
So you know you're off-topic here.
I thought I had posted to comp.lang.c++!
What's the difference with comp.std.c++ then??
How could it rearrange the address space if there is already something
in it?
You reassign the *free* space of course.
If all threads have used up all the address ranges that was assigned to
them, there is no way to malloc another thing!
Suppose you have 3 threads.
You divide all the heap space in 3 address ranges and assign each range
to a thread.
If thread1 uses all of it, and thread 2 and 3 still have mallocated
nothing, then at the next malloc on thread1 it will acquire the mutex
(or whatever it is), reassign globally free space equally among the
three threads (thread1 will own 1/3 + 2/9 of the heap space, not all
contiguous, the other two will own 2/9 each, contiguous), release the
mutex and then malloc.
Of course the delete/free function needs to be a little smarter: if the
thread who deletes is not the same as the thread who has mallocated, it
needs to acquire the mutex and go to the list of the other thread before
releasing the memory, but it would happen only in a minority of cases,
and never when doing malloc/new.
John Doe wrote: Hi all,
I know the standard doesn't care about threads
So you know you're off-topic here.
I thought I had posted to comp.lang.c++!
What's the difference with comp.std.c++ then??
comp.std.c++ discusses the C++ standard.
comp.lang.c++ discusses the C++ language as defined by the C++ standard.
This is off-topic here. Any meaningful discussion of this topic would
need a context (such as a particular threading implementation) that this
group does not provide.
-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.
In article <SI************ ********@speake asy.net>,
"Steven T. Hatton" <su******@setid ava.kushan.aa> wrote: Rolf Magnus wrote:
John Doe wrote:
Hi all,
I know the standard doesn't care about threads
So you know you're off-topic here.
The faq addresses threading issues. That seems to suggest to me they aren't
off topic here.
Additionally the word "thread" is contained in the C++ standard. So I
agree that this is on topic! ;-)
Typically heap memory is treated as global instead of thread local. The
motivation is to allow one thread to delete memory allocated by another
thread.
There is hope that a future C++ standard will address threading issues,
although nothing has been formally proposed yet. Unfettered discussion
of threading and how it relates to C++ could do nothing but help push
that process along.
-Howard
"John Doe" <jo*****@nowher e.com> wrote Hi all,
I know the standard doesn't care about threads (wrongly :-)
Why do newbies ALWAYS want to second-guess the battalion of experts who sit
on the standard committee? This is getting soooo old.
But in current compilers implementation, is the "list" which holds count
of the occupied and free heap addresses SHARED among various threads or
not?
I don't know if I was clear:
Case1: the list which holds count of what is free and what is occupied
is SHARED among all the threads. In this case each
malloc/new/free/delete needs to acquire a mutex.
Case2: list (almost) thread local: no need for mutexes inside the
malloc/new/free/delete implementations , for most calls. So concurrent
access to malloc/new is fast
In this latter case of course there should be some heap address ranges
which are reserved for use by thread1, some are reserved for thread2...
so they don't usually conflict. If some thread fills up its address
range with mallocs, then it has to take a mutex and rearrange the
address ranges dedicated to the various threads so that it can get some
more heap range for the next mallocs...
I need to know the answer to evaluate if for fast
allocations/deallocations it should be wise to use something like an
allocator pool.
Oh another question: are distinct allocator functions for the various
classes automatically generated? It would seem wise to me to divide the
heap (or the section of the heap dedicated to one thread) in address
ranges, and each address range should be used for one class only. In
this way the allocation for various objects of the same type would be
contiguous and the memory would never be fragmented. Of course if one
class finishes its heap range, a reassignment of the heap ranges with
the other objects would have to be made.
See http://www.cs.umass.edu/~emery/hoard/ for answers to most of your
questions.
Claudio Puviani
"Howard Hinnant" <hi*****@metrow erks.com> wrote in message
news:hi******** *************** ****@syrcnyrdrs-01-ge0.nyroc.rr.co m... In article <SI************ ********@speake asy.net>,
"Steven T. Hatton" <su******@setid ava.kushan.aa> wrote:
Rolf Magnus wrote:
John Doe wrote:
> Hi all,
> I know the standard doesn't care about threads
So you know you're off-topic here.
The faq addresses threading issues. That seems to suggest to me they
aren't off topic here.
Additionally the word "thread" is contained in the C++ standard. So I
agree that this is on topic! ;-)
The word 'thread' appears exactly once in the standard
(15.1/2). It's used in the context of exceptions.
Nothing to do with multithreading.
-Mike
In article <UP************ ******@newsread 1.news.pas.eart hlink.net>,
"Mike Wahler" <mk******@mkwah ler.net> wrote: "Howard Hinnant" <hi*****@metrow erks.com> wrote in message
news:hi******** *************** ****@syrcnyrdrs-01-ge0.nyroc.rr.co m... In article <SI************ ********@speake asy.net>,
"Steven T. Hatton" <su******@setid ava.kushan.aa> wrote:
Rolf Magnus wrote:
> John Doe wrote:
>
>> Hi all,
>> I know the standard doesn't care about threads
>
> So you know you're off-topic here.
The faq addresses threading issues. That seems to suggest to me they aren't off topic here.
Additionally the word "thread" is contained in the C++ standard. So I
agree that this is on topic! ;-)
The word 'thread' appears exactly once in the standard
(15.1/2). It's used in the context of exceptions.
Nothing to do with multithreading.
You looked it up! :-) Thanks, I knew somebody would. Perhaps my humor
is now more clear? <sigh> Perhaps not.
<speaking to this community, not just to Mike - who merely relayed a
fact:>
So, is it your opinion that threading as it relates to C++ is off topic
for comp.lang.c++?
Would it be on topic if a threading library had been accepted by the C++
standards committee into the TR1 Library report? What if it had been
proposed, but not accepted? What if people were just thinking about
proposing such a library? Or must topics (such as threading) be
officially voted in, and ratified by the ISO process before they can be
discussed on comp.lang.c++?
Before one answers, it is perhaps instructive to search
comp.lang.c++.m oderated for discussions on this topic. Should the topic
policy on comp.lang.c++ be substantially different than the topic policy
on comp.lang.c++.m oderated? If your answer is yes, perhaps you can be
partially credited with motivating the creation of
comp.lang.c++.m oderated in the first place.
-Howard
Howard Hinnant wrote: In article <UP************ ******@newsread 1.news.pas.eart hlink.net>,
"Mike Wahler" <mk******@mkwah ler.net> wrote:
"Howard Hinnant" <hi*****@metrow erks.com> wrote in message
news:hi******** *************** ****@syrcnyrdrs-01-ge0.nyroc.rr.co m... > In article <SI************ ********@speake asy.net>,
> "Steven T. Hatton" <su******@setid ava.kushan.aa> wrote:
>
> > Rolf Magnus wrote:
> >
> > > John Doe wrote:
> > >
> > >> Hi all,
> > >> I know the standard doesn't care about threads
> > >
> > > So you know you're off-topic here.
> >
> > The faq addresses threading issues. That seems to suggest to me they
aren't > > off topic here.
>
> Additionally the word "thread" is contained in the C++ standard. So I
> agree that this is on topic! ;-)
The word 'thread' appears exactly once in the standard
(15.1/2). It's used in the context of exceptions.
Nothing to do with multithreading.
You looked it up! :-) Thanks, I knew somebody would. Perhaps my humor
is now more clear? <sigh> Perhaps not.
<speaking to this community, not just to Mike - who merely relayed a
fact:>
So, is it your opinion that threading as it relates to C++ is off topic
for comp.lang.c++?
Would it be on topic if a threading library had been accepted by the C++
standards committee into the TR1 Library report? What if it had been
proposed, but not accepted? What if people were just thinking about
proposing such a library? Or must topics (such as threading) be
officially voted in, and ratified by the ISO process before they can be
discussed on comp.lang.c++?
Before one answers, it is perhaps instructive to search
comp.lang.c++.m oderated for discussions on this topic. Should the topic
policy on comp.lang.c++ be substantially different than the topic policy
on comp.lang.c++.m oderated? If your answer is yes, perhaps you can be
partially credited with motivating the creation of
comp.lang.c++.m oderated in the first place.
-Howard
1) Asking what is on topic is off topic. It's not covered in the Standard.
2) Telling people something is off topic is off topic. It's not covered in
the Standard.
3) Asking where to find the Standad is off topic. It's not covered in the
Standard.
4) You are not obligated to consider off topic discussion as relevent to
your choice as to what should be posted here.
Consult the FAQ, and follow your conscience. There /is/ a lot of stuff in
the FAQ, it's worth getting familiar with. If you're not. http://www.parashift.com/c++-faq-lite/
BTW, what is a thread of control?
--
p->m == (*p).m == p[0].m http://www.kdevelop.org http://www.suse.com http://www.mozilla.org This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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