public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "dje at gcc dot gnu.org" <gcc-bugzilla@gcc.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: Tue, 24 Jan 2012 16:46:00 -0000	[thread overview]
Message-ID: <bug-51798-4-WRBV0Rnx8I@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-51798-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51798

--- Comment #5 from David Edelsohn <dje at gcc dot gnu.org> 2012-01-24 15:29:44 UTC ---
Are you suggesting that the existing atomicity support in libstdc++ should be
changed to use ACQ_REL semantics?

libstdc++ uses one function to both acquire and release a lock.  It adds a
positive value (increment) to acquire a lock and a negative value (decrement)
to release a lock.

POWER appears to be the most flexible and delicate platform with respect to
atomic operations and we have been building and testing with my patch for weeks
without problem.  ACQUIRE, RELEASE, ACQ_REL and SEQ_CST does not make a
practical difference in the emitted code on other platforms, so relaxing the
semantics would not cause a problem.


  parent reply	other threads:[~2012-01-24 15:30 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-09 14:31 [Bug libstdc++/51798] New: " dje at gcc dot gnu.org
2012-01-09 14:36 ` [Bug libstdc++/51798] " dje at gcc dot gnu.org
2012-01-09 14:38 ` dje at gcc dot gnu.org
2012-01-09 15:43 ` rguenth at gcc dot gnu.org
2012-01-09 17:12 ` dje at gcc dot gnu.org
2012-01-24  7:45 ` amacleod at redhat dot com
2012-01-24 16:46 ` dje at gcc dot gnu.org [this message]
2012-01-24 16:51 ` amacleod at redhat dot com
2012-01-25 14:27 ` jakub at gcc dot gnu.org
2012-01-25 15:39 ` dje at gcc dot gnu.org
2012-01-25 16:09 ` amacleod at redhat dot com
2012-01-25 16:17 ` dje at gcc dot gnu.org
2012-01-26 13:52 ` jakub at gcc dot gnu.org
2012-01-26 14:38 ` amacleod at redhat dot com
2012-01-26 15:50 ` dje at gcc dot gnu.org
2012-01-26 15:53 ` redi at gcc dot gnu.org
2012-01-26 21:50 ` dje at gcc dot gnu.org
2012-01-26 22:08 ` redi at gcc dot gnu.org
2012-01-27 10:09 ` jakub at gcc dot gnu.org
2012-01-27 11:37 ` jakub at gcc dot gnu.org
2012-01-27 13:03 ` amacleod at redhat dot com
2012-01-27 14:55 ` dje at gcc dot gnu.org
2012-01-27 15:01 ` jakub at gcc dot gnu.org
2012-01-27 15:26 ` dje at gcc dot gnu.org
2012-01-27 20:15 ` bkoz at gcc dot gnu.org
2012-01-27 21:05 ` jakub at gcc dot gnu.org
2012-01-27 21:08 ` jakub at gcc dot gnu.org
2012-02-09  8:46 ` bkoz at gcc dot gnu.org
2012-02-09  9:16 ` redi at gcc dot gnu.org
2012-02-09 20:08 ` bkoz at gcc dot gnu.org
2012-02-09 23:22 ` bkoz at gcc dot gnu.org
2012-02-10 18:21 ` bkoz at gcc dot gnu.org
2012-02-13 21:31 ` rth at gcc dot gnu.org
2012-02-17 21:03 ` bkoz at gcc dot gnu.org

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bug-51798-4-WRBV0Rnx8I@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).