From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25328 invoked by alias); 25 Jan 2012 15:16:16 -0000 Received: (qmail 25316 invoked by uid 22791); 25 Jan 2012 15:16:14 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 25 Jan 2012 15:16:02 +0000 From: "dje at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/51798] [4.7 regression] libstdc++ atomicity performance regression due to __sync_fetch_and_add Date: Wed, 25 Jan 2012 15:39:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: libstdc++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: dje at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.7.0 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-01/txt/msg02944.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51798 --- Comment #8 from David Edelsohn 2012-01-25 15:14:29 UTC --- > At least at this point I'd feel much safer if libstdc++ used just acq_rel > semantics for the all atomic_fetch_and_add places, instead of somewhere acq and > somewhere rel semantics. Can we at least apply the ACQ_REL patch using the new atomic intrinsics? Unfortunately, without my patch, libstdc++ users of atomicity.h (basic_string, shared_ptr) do not distinguish between ACQUIRE and RELEASE, so POWER cannot provide its own atomicity.h with the improved implementation.