From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: pagefault scalability patches From: Benjamin Herrenschmidt In-Reply-To: References: <20050817151723.48c948c7.akpm@osdl.org> Content-Type: text/plain Date: Mon, 22 Aug 2005 12:13:43 +1000 Message-Id: <1124676823.5159.12.camel@gaston> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Linus Torvalds , Andrew Morton , Hugh Dickins , Nick Piggin , linux-mm@kvack.org List-ID: On Wed, 2005-08-17 at 15:51 -0700, Christoph Lameter wrote: > On Wed, 17 Aug 2005, Linus Torvalds wrote: > > > HOWEVER, the fact that it makes the mm counters be atomic just makes it > > pointless. It may help scalability, but it loses the attribute that I > > considered a big win above - it no longer helps the non-contended case (at > > least on x86, a uncontended spinlock is about as expensive as a atomic > > op). > > We are trading 2x (spinlock(page_table_lock), > spin_unlock(page_table_lock)) against one atomic inc. At least on ppc, unlock isn't atomic > > I thought Christoph (Nick?) had a patch to make the counters be > > per-thread, and then just folded back into the mm-struct every once in a > > while? > > Yes I do but I did want want to risk that can of worms becoming entwined > with the page fault scalability patches. -- 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