From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: mm-more-likely-reclaim-madv_sequential-mappings.patch References: <20081015162232.f673fa59.akpm@linux-foundation.org> <200810170043.26922.nickpiggin@yahoo.com.au> <48F77430.80001@redhat.com> <200810171321.40725.nickpiggin@yahoo.com.au> Date: Fri, 17 Oct 2008 18:51:10 +0200 In-Reply-To: <200810171321.40725.nickpiggin@yahoo.com.au> (Nick Piggin's message of "Fri, 17 Oct 2008 13:21:40 +1100") Message-ID: <87k5c74135.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Rik van Riel , Andrew Morton , linux-mm@kvack.org List-ID: Nick Piggin writes: > On Friday 17 October 2008 04:04, Rik van Riel wrote: >> Nick Piggin wrote: >> > ClearPageReferenced I don't know if it should be cleared like this. >> > PageReferenced is more of a bit for the mark_page_accessed state machine, >> > rather than the pte_young stuff. Although when unmapping, the latter >> > somewhat collapses back to the former, but I don't know if there is a >> > very good reason to fiddle with it here. >> > >> > Ignoring the young bit in the pte for sequential hint maybe is OK (and >> > seems to be effective as per the benchmarks). But I would prefer not to >> > merge the PageReferenced parts unless they get their own justification. >> >> Unless we clear the PageReferenced bit, we will still activate >> the page - even if its only access came through a sequential >> mapping. >> >> Faulting the page into the sequential mapping ends up setting >> PageReferenced, IIRC. > > Yes I see. But that's stupid because then you can end up putting a > sequential mapping on a page, and cause that to deactivate somebody > else's references... and the deactivation _only_ happens if the > sequential mapping pte is young and the page happens not to be > active, which is totally arbitrary. Another access would mean another young PTE, which we will catch as a proper reference sooner or later while walking the mappings, no? Hannes -- 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