From mboxrd@z Thu Jan 1 00:00:00 1970 From: Toshi Kani Subject: Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier. Date: Fri, 23 Aug 2013 10:14:08 -0600 Message-ID: <1377274448.10300.777.camel@misato.fc.hp.com> References: <20130821204041.GC2436@htj.dyndns.org> <1377124595.10300.594.camel@misato.fc.hp.com> <20130822033234.GA2413@htj.dyndns.org> <1377186729.10300.643.camel@misato.fc.hp.com> <20130822183130.GA3490@mtj.dyndns.org> <1377202292.10300.693.camel@misato.fc.hp.com> <20130822202158.GD3490@mtj.dyndns.org> <1377205598.10300.715.camel@misato.fc.hp.com> <20130822212111.GF3490@mtj.dyndns.org> <1377209861.10300.756.camel@misato.fc.hp.com> <20130823130440.GC10322@mtj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from g4t0015.houston.hp.com ([15.201.24.18]:39082 "EHLO g4t0015.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754379Ab3HWQPj (ORCPT ); Fri, 23 Aug 2013 12:15:39 -0400 In-Reply-To: <20130823130440.GC10322@mtj.dyndns.org> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Tejun Heo Cc: Zhang Yanfei , Tang Chen , konrad.wilk@oracle.com, robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, akpm@linux-foundation.org, trenn@suse.de, yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org, mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, zhangyanfei@cn.fujitsu.com, yanghy@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Hello, On Fri, 2013-08-23 at 09:04 -0400, Tejun Heo wrote: > On Thu, Aug 22, 2013 at 04:17:41PM -0600, Toshi Kani wrote: > > I am relatively new to Linux, so I am not a good person to elaborate > > this. From my experience on other OS, huge pages helped for the kernel, > > but did not necessarily help user applications. It depended on > > applications, which were not niche cases. But Linux may be different, > > so I asked since you seemed confident. I'd appreciate if you can point > > us some data that endorses your statement. > > We are talking about the kernel linear mapping which is created during > early boot, so if it's available and useable there's no reason not to > use it. Exceptions would be earlier processors which didn't do 1G > mappings or e820 maps with a lot of holes. For CPUs used in NUMA > configurations, the former has been history for a bit now. Can't be > sure about the latter but it'd be surprising for that to affect large > amount of memory in the systems that are of interest here. Ooh, that > reminds me that we probably wanna go back to 1G + MTRR mapping under > 4G. We're currently creating a lot of mapping holes. Thanks for the explanation. > > My worry is that the code is unlikely tested with the special logic when > > someone makes code changes to the page tables. Such code can easily be > > broken in future. > > Well, I wouldn't consider flipping the direction of allocation to be > particularly difficult to get right especially when compared to > bringing in ACPI tables into the mix. > > > To answer your other question/email, I believe Tang's next step is to > > support local page tables. This is why we think pursing SRAT earlier is > > the right direction. > > Given 1G mappings, is that even a worthwhile effort? I'm getting even > more more skeptical. With 1G mappings, I agree that it won't make much difference. I still think acpi table info should be available earlier, but I do not think I can convince you on this. This can be religious debate. Tang, what do you think? Are you OK to try Tejun's suggestion as well? Thanks, -Toshi From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id 84B5C6B0032 for ; Fri, 23 Aug 2013 12:15:39 -0400 (EDT) Message-ID: <1377274448.10300.777.camel@misato.fc.hp.com> Subject: Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier. From: Toshi Kani Date: Fri, 23 Aug 2013 10:14:08 -0600 In-Reply-To: <20130823130440.GC10322@mtj.dyndns.org> References: <20130821204041.GC2436@htj.dyndns.org> <1377124595.10300.594.camel@misato.fc.hp.com> <20130822033234.GA2413@htj.dyndns.org> <1377186729.10300.643.camel@misato.fc.hp.com> <20130822183130.GA3490@mtj.dyndns.org> <1377202292.10300.693.camel@misato.fc.hp.com> <20130822202158.GD3490@mtj.dyndns.org> <1377205598.10300.715.camel@misato.fc.hp.com> <20130822212111.GF3490@mtj.dyndns.org> <1377209861.10300.756.camel@misato.fc.hp.com> <20130823130440.GC10322@mtj.dyndns.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Zhang Yanfei , Tang Chen , konrad.wilk@oracle.com, robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, akpm@linux-foundation.org, trenn@suse.de, yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org, mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, zhangyanfei@cn.fujitsu.com, yanghy@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Hello, On Fri, 2013-08-23 at 09:04 -0400, Tejun Heo wrote: > On Thu, Aug 22, 2013 at 04:17:41PM -0600, Toshi Kani wrote: > > I am relatively new to Linux, so I am not a good person to elaborate > > this. From my experience on other OS, huge pages helped for the kernel, > > but did not necessarily help user applications. It depended on > > applications, which were not niche cases. But Linux may be different, > > so I asked since you seemed confident. I'd appreciate if you can point > > us some data that endorses your statement. > > We are talking about the kernel linear mapping which is created during > early boot, so if it's available and useable there's no reason not to > use it. Exceptions would be earlier processors which didn't do 1G > mappings or e820 maps with a lot of holes. For CPUs used in NUMA > configurations, the former has been history for a bit now. Can't be > sure about the latter but it'd be surprising for that to affect large > amount of memory in the systems that are of interest here. Ooh, that > reminds me that we probably wanna go back to 1G + MTRR mapping under > 4G. We're currently creating a lot of mapping holes. Thanks for the explanation. > > My worry is that the code is unlikely tested with the special logic when > > someone makes code changes to the page tables. Such code can easily be > > broken in future. > > Well, I wouldn't consider flipping the direction of allocation to be > particularly difficult to get right especially when compared to > bringing in ACPI tables into the mix. > > > To answer your other question/email, I believe Tang's next step is to > > support local page tables. This is why we think pursing SRAT earlier is > > the right direction. > > Given 1G mappings, is that even a worthwhile effort? I'm getting even > more more skeptical. With 1G mappings, I agree that it won't make much difference. I still think acpi table info should be available earlier, but I do not think I can convince you on this. This can be religious debate. Tang, what do you think? Are you OK to try Tejun's suggestion as well? Thanks, -Toshi -- 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