From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4645DCA2.80408@cosmosbay.com> Date: Sat, 12 May 2007 17:26:26 +0200 From: Eric Dumazet MIME-Version: 1.0 Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex References: <20070511131541.992688403@chello.nl> <1178964103.6810.55.camel@twins> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Return-Path: To: Esben Nielsen Cc: Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Andrew Morton , Ingo Molnar , Thomas Gleixner , Nick Piggin List-ID: Esben Nielsen a ecrit : > > > On Sat, 12 May 2007, Peter Zijlstra wrote: > >> 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. >> >> > If PI wasn't a concern for mainline, why is PI futexes merged into the > mainline? If you really care about futexes and mmap_sem, just use private futexes, since they dont use mmap_sem at all. -- 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