From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joshua Kinard Subject: Re: [PATCH v4 0/2] mm/highmem: make kmap cache coloring aware Date: Mon, 25 Aug 2014 22:41:07 -0400 Message-ID: <53FBF3C3.90509@gentoo.org> References: <1406941899-19932-1-git-send-email-jcmvbkbc@gmail.com> <20140825171600.GH25892@linux-mips.org> <53FBCD09.1050003@gentoo.org> <53FBD676.8080307@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53FBD676.8080307@gmail.com> Sender: owner-linux-mm@kvack.org To: David Daney Cc: Ralf Baechle , Max Filippov , linux-xtensa@linux-xtensa.org, Chris Zankel , Marc Gauthier , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, David Rientjes , Andrew Morton , Leonid Yegoshin , Steven Hill List-Id: linux-arch.vger.kernel.org On 08/25/2014 20:36, David Daney wrote: > On 08/25/2014 04:55 PM, Joshua Kinard wrote: >> On 08/25/2014 13:16, Ralf Baechle wrote: >>> On Sat, Aug 02, 2014 at 05:11:37AM +0400, Max Filippov wrote: >>> >>>> this series adds mapping color control to the generic kmap code, allowing >>>> architectures with aliasing VIPT cache to use high memory. There's also >>>> use example of this new interface by xtensa. >>> >>> I haven't actually ported this to MIPS but it certainly appears to be >>> the right framework to get highmem aliases handled on MIPS, too. >>> >>> Though I still consider increasing PAGE_SIZE to 16k the preferable >>> solution because it will entirly do away with cache aliases. >> >> Won't setting PAGE_SIZE to 16k break some existing userlands (o32)? I use a >> 4k PAGE_SIZE because the last few times I've tried 16k or 64k, init won't >> load (SIGSEGVs or such, which panicks the kernel). >> > > It isn't supposed to break things. Using "stock" toolchains should result > in executables that will run with any page size. > > In the past, some geniuses came up with some linker (ld) patches that, in > order to save a few KB of RAM, produced executables that ran only on 4K pages. > > There were some equally astute Debian emacs package maintainers that were > carrying emacs patches into Debian that would not work on non-4K page size > systems. > > That said, I think such thinking should be punished. The punishment should > be to not have their software run when we select non-4K page sizes. The > vast majority of prepackaged software runs just fine with a larger page size. Well, it does appear to mostly work now w/ 16k PAGE_SIZE. The Octane booted into userland with just a couple of "illegal instruction" errors from 'rm' and 'mdadm'. I wonder if that's tied to a hardcoded PAGE_SIZE somewhere. Have to dig around and find something that reproduces the problem on demand. -- Joshua Kinard Gentoo/MIPS kumba@gentoo.org 4096R/D25D95E3 2011-03-28 "The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between." --Emperor Turhan, Centauri Republic -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from qmta14.westchester.pa.mail.comcast.net ([76.96.59.212]:58141 "EHLO qmta14.westchester.pa.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755559AbaHZCrQ (ORCPT ); Mon, 25 Aug 2014 22:47:16 -0400 Message-ID: <53FBF3C3.90509@gentoo.org> Date: Mon, 25 Aug 2014 22:41:07 -0400 From: Joshua Kinard MIME-Version: 1.0 Subject: Re: [PATCH v4 0/2] mm/highmem: make kmap cache coloring aware References: <1406941899-19932-1-git-send-email-jcmvbkbc@gmail.com> <20140825171600.GH25892@linux-mips.org> <53FBCD09.1050003@gentoo.org> <53FBD676.8080307@gmail.com> In-Reply-To: <53FBD676.8080307@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Daney Cc: Ralf Baechle , Max Filippov , linux-xtensa@linux-xtensa.org, Chris Zankel , Marc Gauthier , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, David Rientjes , Andrew Morton , Leonid Yegoshin , Steven Hill Message-ID: <20140826024107.YrZdvv8Nc13SSjdYI9U6Pd4-3FI9EUwfAVJM2lGDF3s@z> On 08/25/2014 20:36, David Daney wrote: > On 08/25/2014 04:55 PM, Joshua Kinard wrote: >> On 08/25/2014 13:16, Ralf Baechle wrote: >>> On Sat, Aug 02, 2014 at 05:11:37AM +0400, Max Filippov wrote: >>> >>>> this series adds mapping color control to the generic kmap code, allowing >>>> architectures with aliasing VIPT cache to use high memory. There's also >>>> use example of this new interface by xtensa. >>> >>> I haven't actually ported this to MIPS but it certainly appears to be >>> the right framework to get highmem aliases handled on MIPS, too. >>> >>> Though I still consider increasing PAGE_SIZE to 16k the preferable >>> solution because it will entirly do away with cache aliases. >> >> Won't setting PAGE_SIZE to 16k break some existing userlands (o32)? I use a >> 4k PAGE_SIZE because the last few times I've tried 16k or 64k, init won't >> load (SIGSEGVs or such, which panicks the kernel). >> > > It isn't supposed to break things. Using "stock" toolchains should result > in executables that will run with any page size. > > In the past, some geniuses came up with some linker (ld) patches that, in > order to save a few KB of RAM, produced executables that ran only on 4K pages. > > There were some equally astute Debian emacs package maintainers that were > carrying emacs patches into Debian that would not work on non-4K page size > systems. > > That said, I think such thinking should be punished. The punishment should > be to not have their software run when we select non-4K page sizes. The > vast majority of prepackaged software runs just fine with a larger page size. Well, it does appear to mostly work now w/ 16k PAGE_SIZE. The Octane booted into userland with just a couple of "illegal instruction" errors from 'rm' and 'mdadm'. I wonder if that's tied to a hardcoded PAGE_SIZE somewhere. Have to dig around and find something that reproduces the problem on demand. -- Joshua Kinard Gentoo/MIPS kumba@gentoo.org 4096R/D25D95E3 2011-03-28 "The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between." --Emperor Turhan, Centauri Republic