From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 8 Jan 2008 11:08:03 +0100 From: Nick Piggin Subject: Re: [rfc][patch 0/4] VM_MIXEDMAP patchset with s390 backend Message-ID: <20080108100803.GA24570@wotan.suse.de> References: <20071214133817.GB28555@wotan.suse.de> <20071214134106.GC28555@wotan.suse.de> <476A73F0.4070704@de.ibm.com> <476A7D21.7070607@de.ibm.com> <20071221004556.GB31040@wotan.suse.de> <476B9000.2090707@de.ibm.com> <20071221102052.GB28484@wotan.suse.de> <476B96D6.2010302@de.ibm.com> <20071221104701.GE28484@wotan.suse.de> <1199784954.25114.27.camel@cotte.boeblingen.de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1199784954.25114.27.camel@cotte.boeblingen.de.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Carsten Otte Cc: carsteno@de.ibm.com, Jared Hulbert , Linux Memory Management List , Martin Schwidefsky , Heiko Carstens List-ID: On Tue, Jan 08, 2008 at 10:35:54AM +0100, Carsten Otte wrote: > Am Freitag, den 21.12.2007, 11:47 +0100 schrieb Nick Piggin: > > BTW. having a per-arch function sounds reasonable for a start. I'd just give > > it a long name, so that people don't start using it for weird things ;) > > mixedmap_refcount_pfn() or something. > Based on our previous discussion, and based on previous patches by Jared > and Nick, this patch series makes XIP without struct page backing usable > on s390 architecture. > This patch set includes: > 1/4: mm: introduce VM_MIXEDMAP mappings from Jared Hulbert, modified to > use an arch-callback to identify whether or not a pfn needs refcounting > 2/4: xip: support non-struct page memory from Nick Piggin, modified to > use an arch-callback to identify whether or not a pfn needs refcounting > 3/4: s390: remove struct page entries for z/VM DCSS memory segments > 4/4: s390: proof of concept implementation of mixedmap_refcount_pfn() > for s390 using list-walk Nice! I'm glad that the xip support didn't need anything further than the mixedmap_refcount_pfn for s390. Hopefully it proves to be stable under further testing. I'm just curious (or forgetful) as to why s390's pfn_valid does not walk your memory segments? (That would allow the s390 proof of concept to be basically a noop, and mixedmap_refcount_pfn will only be required when we start using another pte bit. > Above stack seems to work well, I did some sniff-testing applied on top > of Linus' current git tree. We do want to spend a precious pte bit to > speed up this callback, therefore patch 4/4 will get replaced. I think using another bit in the pte for special mappings is reasonable. As I posted in my earlier patch, we can also use it to simplify vm_normal_page, and it facilitates a lock free get_user_pages. Anyway, hmm... I guess we should probably get these patches into -mm and then upstream soon. Any objections from anyone? Do you guys have performance / stress testing for xip? -- 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