From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Date: Fri, 10 Dec 2004 05:06:16 +0000 Subject: Re: page fault scalability patch V12 [0/7]: Overview and Message-Id: <1102655177.22746.29.camel@gaston> List-Id: References: <41B92567.8070809@yahoo.com.au> <41B92C11.80106@yahoo.com.au> In-Reply-To: <41B92C11.80106@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Nick Piggin Cc: Hugh Dickins , Christoph Lameter , Linus Torvalds , Andrew Morton , linux-mm@kvack.org, linux-ia64@vger.kernel.org, Linux Kernel list On Fri, 2004-12-10 at 15:54 +1100, Nick Piggin wrote: > Nick Piggin wrote: > > > Yep, the update_mmu_cache issue is real. There is a parallel problem > > that is update_mmu_cache can be called on a pte who's page has since > > been evicted and reused. Again, that looks safe on IA64, but maybe > > not on other architectures. > > > > It can be solved by moving lru_cache_add to after update_mmu_cache in > > all cases but the "update accessed bit" type fault. I solved that by > > simply defining that out for architectures that don't need it - a raced > > fault will simply get repeated if need be. > > > > The page-freed-before-update_mmu_cache issue can be solved in that way, > not the set_pte and update_mmu_cache not performed under the same ptl > section issue that you raised. What is the problem with update_mmu_cache ? It doesn't need to be done in the same lock section since it's approx. equivalent to a HW fault, which doesn't take the ptl... Ben.