From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 28 Jan 2007 16:17:00 +0100 From: Ingo Molnar Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c Message-ID: <20070128151700.GA7644@elte.hu> References: <1169993494.10987.23.camel@lappy> <20070128144933.GD16552@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070128144933.GD16552@infradead.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Hellwig , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton List-ID: * Christoph Hellwig wrote: > On Sun, Jan 28, 2007 at 03:11:34PM +0100, Peter Zijlstra wrote: > > Eradicate global locks. > > > > - kmap_lock is removed by extensive use of atomic_t, a new flush > > scheme and modifying set_page_address to only allow NULL<->virt > > transitions. > > What's the point for this? [...] scalability. I did lock profiling on the -rt kernel, which exposes such things nicely. Half of the lock contention events during kernel compile were due to kmap(). (The system had 2 GB of RAM, so 40% lowmem, 60% highmem.) > [...] In doubt we just need to convert that caller to kmap_atomic. the pagecache ones cannot be converted to kmap_atomic, because we can block while holding them. Plus kmap_atomic is quite a bit slower than this scalable version of kmap(). Ingo ps. please fix your mailer to not emit Mail-Followup-To headers. In Mutt you can do this via "set followup_to=no" in your .muttrc. -- 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