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* [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency @ 2015-03-11 19:00 klemensbaum at gmail dot com 2015-03-11 19:14 ` [Bug libstdc++/65393] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: klemensbaum at gmail dot com @ 2015-03-11 19:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393 Bug ID: 65393 Summary: std::thread shared_ptr inefficiency Product: gcc Version: unknown Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: klemensbaum at gmail dot com The std::thread implementation passes around shared_ptr instances by value in multiple places where they could be moved: 1) in the function void thread::_M_start_thread(__shared_base_type __b) the line _M_start_thread(__b, nullptr); could be changed to _M_start_thread(std::move(__b), nullptr); or alternatively take __shared_base_type by "universal reference" and forward it into the other _M_start_thread overload. 2) in the function void thread::_M_start_thread(__shared_base_type __b, void (*)()) the lines __b->_M_this_ptr = __b; int __e = __gthread_create(&_M_id._M_thread, &execute_native_thread_routine, __b.get()); could be changed to auto __p = __b.get(); __b->_M_this_ptr = std::move(__b); int __e = __gthread_create(&_M_id._M_thread, &execute_native_thread_routine, __p); 3) Finally, the use of shared_ptr seems wholly unnecessarily. This can likely be implemented more cleanly with unique_ptr, and more efficiently, since it avoids the extra heap space for the reference count and all of the atomic ops. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/65393] std::thread shared_ptr inefficiency 2015-03-11 19:00 [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency klemensbaum at gmail dot com @ 2015-03-11 19:14 ` redi at gcc dot gnu.org 2015-06-16 17:54 ` redi at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2015-03-11 19:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Last reconfirmed| |2015-03-11 Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org Target Milestone|--- |6.0 Ever confirmed|0 |1 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Klemens from comment #0) > could be changed to > _M_start_thread(std::move(__b), nullptr); > > or alternatively take __shared_base_type by "universal reference" and > forward it into the other _M_start_thread overload. (They're called forwarding references now) That would require making the function a template, for no benefit. It should be moved. In general, these inefficiencies are pretty tiny compared to the cost of launching a new thread that happens immediately after. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/65393] std::thread shared_ptr inefficiency 2015-03-11 19:00 [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency klemensbaum at gmail dot com 2015-03-11 19:14 ` [Bug libstdc++/65393] " redi at gcc dot gnu.org @ 2015-06-16 17:54 ` redi at gcc dot gnu.org 2015-06-22 15:54 ` redi at gcc dot gnu.org 2015-09-29 12:56 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2015-06-16 17:54 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393 --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- Author: redi Date: Tue Jun 16 17:53:52 2015 New Revision: 224530 URL: https://gcc.gnu.org/viewcvs?rev=224530&root=gcc&view=rev Log: PR libstdc++/65393 * src/c++11/thread.cc (thread::_M_make_thread): Replace shared_ptr copies with moves. Modified: trunk/libstdc++-v3/ChangeLog trunk/libstdc++-v3/src/c++11/thread.cc ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/65393] std::thread shared_ptr inefficiency 2015-03-11 19:00 [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency klemensbaum at gmail dot com 2015-03-11 19:14 ` [Bug libstdc++/65393] " redi at gcc dot gnu.org 2015-06-16 17:54 ` redi at gcc dot gnu.org @ 2015-06-22 15:54 ` redi at gcc dot gnu.org 2015-09-29 12:56 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2015-06-22 15:54 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393 --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Author: redi Date: Mon Jun 22 15:53:27 2015 New Revision: 224742 URL: https://gcc.gnu.org/viewcvs?rev=224742&root=gcc&view=rev Log: Backport from mainline 2015-06-16 Jonathan Wakely <jwakely@redhat.com> PR libstdc++/65393 * src/c++11/thread.cc (thread::_M_make_thread): Replace shared_ptr copies with moves. Modified: branches/gcc-5-branch/libstdc++-v3/ChangeLog branches/gcc-5-branch/libstdc++-v3/src/c++11/thread.cc ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/65393] std::thread shared_ptr inefficiency 2015-03-11 19:00 [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency klemensbaum at gmail dot com ` (2 preceding siblings ...) 2015-06-22 15:54 ` redi at gcc dot gnu.org @ 2015-09-29 12:56 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2015-09-29 12:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution|--- |FIXED --- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- shared_ptr is no longer used on trunk. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-09-29 12:56 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-03-11 19:00 [Bug libstdc++/65393] New: std::thread shared_ptr inefficiency klemensbaum at gmail dot com 2015-03-11 19:14 ` [Bug libstdc++/65393] " redi at gcc dot gnu.org 2015-06-16 17:54 ` redi at gcc dot gnu.org 2015-06-22 15:54 ` redi at gcc dot gnu.org 2015-09-29 12:56 ` redi at gcc dot gnu.org
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