From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id 4E5816B006E for ; Fri, 26 Jul 2013 17:37:12 -0400 (EDT) Received: by mail-ve0-f181.google.com with SMTP id jz10so1644935veb.12 for ; Fri, 26 Jul 2013 14:37:11 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20130726211844.GB8508@moon> References: <20130726201807.GJ8661@moon> <20130726211844.GB8508@moon> From: Andy Lutomirski Date: Fri, 26 Jul 2013 14:36:51 -0700 Message-ID: Subject: Re: [PATCH] mm: Save soft-dirty bits on file pages Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Cyrill Gorcunov Cc: Linux MM , LKML , Pavel Emelyanov , Andrew Morton , Matt Mackall , Xiao Guangrong , Marcelo Tosatti , KOSAKI Motohiro , Stephen Rothwell On Fri, Jul 26, 2013 at 2:18 PM, Cyrill Gorcunov wrote: > On Fri, Jul 26, 2013 at 01:55:04PM -0700, Andy Lutomirski wrote: >> On Fri, Jul 26, 2013 at 1:18 PM, Cyrill Gorcunov wrote: >> > Andy reported that if file page get reclaimed we loose soft-dirty bit >> > if it was there, so save _PAGE_BIT_SOFT_DIRTY bit when page address >> > get encoded into pte entry. Thus when #pf happens on such non-present >> > pte we can restore it back. >> > >> >> Unless I'm misunderstanding this, it's saving the bit in the >> non-present PTE. This sounds wrong -- what happens if the entire pmd > > It's the same as encoding pgoff in pte entry (pte is not present), > but together with pgoff we save soft-bit status, later on #pf we decode > pgoff and restore softbit back if it was there, pte itself can't disappear > since it holds pgoff information. Isn't that only the case for nonlinear mappings? --Andy -- 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