From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate8.de.ibm.com (8.13.8/8.13.8) with ESMTP id m2C8kjA4181708 for ; Wed, 12 Mar 2008 08:46:45 GMT Received: from d12av02.megacenter.de.ibm.com (d12av02.megacenter.de.ibm.com [9.149.165.228]) by d12nrmr1607.megacenter.de.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m2C8kjqK1921146 for ; Wed, 12 Mar 2008 09:46:45 +0100 Received: from d12av02.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av02.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m2C8kibg007622 for ; Wed, 12 Mar 2008 09:46:45 +0100 Subject: Re: [patch 0/7] [rfc] VM_MIXEDMAP, pte_special, xip work From: Martin Schwidefsky Reply-To: schwidefsky@de.ibm.com In-Reply-To: <200803121633.34539.nickpiggin@yahoo.com.au> References: <20080311104653.995564000@nick.local0.net> <20080311213525.a5994894.akpm@linux-foundation.org> <200803121633.34539.nickpiggin@yahoo.com.au> Content-Type: text/plain Date: Wed, 12 Mar 2008 09:46:42 +0100 Message-Id: <1205311602.28247.7.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , npiggin@nick.local0.net, Linus Torvalds , Jared Hulbert , Carsten Otte , Heiko Carstens , linux-mm@kvack.org List-ID: On Wed, 2008-03-12 at 16:33 +1100, Nick Piggin wrote: > s390 is slightly different because it doesn't use a standard memory model > but something more dynamic. It doesn't quite do the right thing here, so > it uses pte_special. It could possibly tighten up pfn_valid, however I > think there are various reasons why they don't want to (one is that they > need to take a global lock in order to search their list of extents; > which will suck for VM_MIXEDMAP performance). Indeed. Under z/VM we have mappable memory segments named DCSS that can have different types. Dependend on the type we either want to do refcounting (exclusive write for memory hotplug) or not (read-only shared for memory sharing). pfn_valid() would have to scan the list of DCCSes to find out which type the segment has. That is way too expensive. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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