From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 17 Aug 2005 15:51:48 -0700 (PDT) From: Christoph Lameter Subject: Re: pagefault scalability patches In-Reply-To: Message-ID: References: <20050817151723.48c948c7.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Andrew Morton , Hugh Dickins , Nick Piggin , linux-mm@kvack.org List-ID: 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. > > 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