Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754395Ab3CVBOz (ORCPT ); Thu, 21 Mar 2013 21:14:55 -0400 Received: from g4t0017.houston.hp.com ([15.201.24.20]:44978 "EHLO g4t0017.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753331Ab3CVBOy (ORCPT ); Thu, 21 Mar 2013 21:14:54 -0400 Message-ID: <1363914891.31240.62.camel@buesod1.americas.hpqcorp.net> Subject: Re: [PATCH 7/7] ipc,sem: fine grained locking for semtimedop From: Davidlohr Bueso To: Rik van Riel Cc: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hhuang@redhat.com, jason.low2@hp.com, walken@google.com, lwoodman@redhat.com, chegu_vinod@hp.com, Rik van Riel Date: Thu, 21 Mar 2013 18:14:51 -0700 In-Reply-To: <1363809337-29718-8-git-send-email-riel@surriel.com> References: <1363809337-29718-1-git-send-email-riel@surriel.com> <1363809337-29718-8-git-send-email-riel@surriel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 (3.4.4-2.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1614 Lines: 40 On Wed, 2013-03-20 at 15:55 -0400, Rik van Riel wrote: > Introduce finer grained locking for semtimedop, to handle the > common case of a program wanting to manipulate one semaphore > from an array with multiple semaphores. > > If the call is a semop manipulating just one semaphore in > an array with multiple semaphores, only take the lock for > that semaphore itself. > > If the call needs to manipulate multiple semaphores, or > another caller is in a transaction that manipulates multiple > semaphores, the sem_array lock is taken, as well as all the > locks for the individual semaphores. > > On a 24 CPU system, performance numbers with the semop-multi > test with N threads and N semaphores, look like this: > > vanilla Davidlohr's Davidlohr's + Davidlohr's + > threads patches rwlock patches v3 patches > 10 610652 726325 1783589 2142206 > 20 341570 365699 1520453 1977878 > 30 288102 307037 1498167 2037995 > 40 290714 305955 1612665 2256484 > 50 288620 312890 1733453 2650292 > 60 289987 306043 1649360 2388008 > 70 291298 306347 1723167 2717486 > 80 290948 305662 1729545 2763582 > 90 290996 306680 1736021 2757524 > 100 292243 306700 1773700 3059159 > > Signed-off-by: Rik van Riel > Suggested-by: Linus Torvalds Acked-by: Davidlohr Bueso -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/