From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: mm-more-likely-reclaim-madv_sequential-mappings.patch Date: Sat, 18 Oct 2008 12:30:33 +1100 References: <20081015162232.f673fa59.akpm@linux-foundation.org> <200810171321.40725.nickpiggin@yahoo.com.au> <87k5c74135.fsf@saeurebad.de> In-Reply-To: <87k5c74135.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200810181230.33688.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Johannes Weiner Cc: Rik van Riel , Andrew Morton , linux-mm@kvack.org List-ID: On Saturday 18 October 2008 03:51, Johannes Weiner wrote: > 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? No. Another access could come via read/write, or be subsequently unmapped and put into PG_referenced. -- 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