From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex From: Peter Zijlstra In-Reply-To: References: <20070511131541.992688403@chello.nl> Content-Type: text/plain Date: Sat, 12 May 2007 12:01:43 +0200 Message-Id: <1178964103.6810.55.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Esben Nielsen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Andrew Morton , Ingo Molnar , Thomas Gleixner , Nick Piggin List-ID: On Sat, 2007-05-12 at 11:27 +0200, Esben Nielsen wrote: > > On Fri, 11 May 2007, Peter Zijlstra wrote: > > > > > I was toying with a scalable rw_mutex and found that it gives ~10% reduction in > > system time on ebizzy runs (without the MADV_FREE patch). > > > > You break priority enheritance on user space futexes! :-( > The problems is that the futex waiter have to take the mmap_sem. And as > your rw_mutex isn't PI enabled you get priority inversions :-( Do note that rwsems have no PI either. PI is not a concern for mainline - yet, I do have ideas here though. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org