Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753599AbdLMQAD (ORCPT ); Wed, 13 Dec 2017 11:00:03 -0500 Received: from mga09.intel.com ([134.134.136.24]:21429 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753444AbdLMP76 (ORCPT ); Wed, 13 Dec 2017 10:59:58 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,397,1508828400"; d="scan'208";a="11547259" Date: Thu, 14 Dec 2017 00:02:42 +0800 From: Yu Chen To: "Rafael J. Wysocki" Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , Lukas Wunner , "Rafael J . Wysocki" , Len Brown , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Rui Zhang Subject: Re: [PATCH 3/3][RFC/RFT] PM / sleep: Do not delay the synchronization of MTRR during resume Message-ID: <20171213160242.GB29572@yu-chen.sh.intel.com> References: <1613777.Al2QaFApID@aspire.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1613777.Al2QaFApID@aspire.rjw.lan> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5308 Lines: 135 On Wed, Dec 13, 2017 at 01:31:50AM +0100, Rafael J. Wysocki wrote: > On Tuesday, October 31, 2017 10:58:50 AM CET Yu Chen wrote: > > From: Chen Yu > > > > Sometimes it is too late for the APs to synchronize the MTRR > > after all the APs have been brought up. In some cases the BIOS > > might scribble the MTRR across suspend/resume, as a result we > > might get insane MTRR after resumed back, thus every instruction > > run on this AP would be extremely slow if it happended to be 'uncached' > > in the MTRR, although after all the APs have been brought up, the > > delayed invoking of set_mtrr_state() will adjust the MTRR on APs > > thus brings everything back to normal. In practice it is necessary > > to synchronize the MTRR as early as possible to get it fixed during > > each AP's online. And this is what this patch does. > > > > Moreover, since we have put the synchronization earlier, there is > > a side effect that, during each AP's online, the other cpus already > > online will be forced stopped to run mtrr_rendezvous_handler() and > > reprogram the MTRR again and again. This symptom can be lessened > > by checking if this cpu has already finished the synchronization > > during the enable_nonboot_cpus() stage, if it is, we can safely > > bypass the reprogramming action. (We can not bypass the > > mtrr_rendezvous_handler(), because the other online cpus must be > > stopped running the VMX transaction while one cpu is updating > > its MTRR, which is described here: > > Commit d0af9eed5aa9 ("x86, pat/mtrr: Rendezvous all the cpus for > > MTRR/PAT init") > > > > This patch does not impact the normal boot up and cpu hotplug. > > > > On a platform with insane MTRR after resumed, > > 1 .before this patch: > > [ 619.810899] Enabling non-boot CPUs ... > > [ 619.825537] smpboot: Booting Node 0 Processor 1 APIC 0x2 > > [ 621.723809] CPU1 is up > > [ 621.840228] smpboot: Booting Node 0 Processor 3 APIC 0x3 > > [ 626.690900] CPU3 is up > > > > So it took cpu1 621.723809 - 619.825537 = 1898.272 ms, and > > cpu3 626.690900 - 621.840228 = 4850.672 ms. > > > > 2. after this patch: > > [ 106.931790] smpboot: Booting Node 0 Processor 1 APIC 0x2 > > [ 106.948360] CPU1 is up > > [ 106.986534] smpboot: Booting Node 0 Processor 3 APIC 0x3 > > [ 106.990702] CPU3 is up > > > > It took cpu1 106.948360 - 106.931790 = 16.57 ms, and > > cpu3 106.990702 - 106.986534 = 4.16 ms. > > > > For comparison, I also verify the suspend on a 88 cpus Xeon Broadwell > > platform, and the result also shows that with this patch applied, > > the overall APs online time has decreased a little bit, I think this > > is because after we synchronize the MTRR earlier, the MTRRs also get > > updated to the correct value earlier. > > > > I've tested 5 times each, before/after the patch applied: > > > > 1. before this patch: > > [ 64.549430] Enabling non-boot CPUs ... > > [ 66.253304] End enabling non-boot CPUs > > > > overall cpu online: 1.703874 second > > > > [ 62.159063] Enabling non-boot CPUs ... > > [ 64.483443] End enabling non-boot CPUs > > > > overall cpu online: 2.32438 second > > > > [ 58.351449] Enabling non-boot CPUs ... > > [ 60.796951] End enabling non-boot CPUs > > > > overall cpu online: 2.445502 second > > > > [ 64.491317] Enabling non-boot CPUs ... > > [ 66.996208] End enabling non-boot CPUs > > > > overall cpu online: 2.504891 second > > > > [ 60.593235] Enabling non-boot CPUs ... > > [ 63.397886] End enabling non-boot CPUs > > > > overall cpu online: 2.804651 second > > > > average: 2.3566596 second > > > > 2. after this patch: > > > > [ 66.077368] Enabling non-boot CPUs ... > > [ 68.343374] End enabling non-boot CPUs > > > > overall cpu online: 2.266006 second > > > > [ 64.594605] Enabling non-boot CPUs ... > > [ 66.092688] End enabling non-boot CPUs > > > > overall cpu online: 1.498083 second > > > > [ 64.778546] Enabling non-boot CPUs ... > > [ 66.277577] End enabling non-boot CPUs > > > > overall cpu online: 1.499031 second > > > > [ 63.773091] Enabling non-boot CPUs ... > > [ 65.601637] End enabling non-boot CPUs > > > > overall cpu online: 1.828546 second > > > > [ 64.638855] Enabling non-boot CPUs ... > > [ 66.327098] End enabling non-boot CPUs > > > > overall cpu online: 1.688243 second > > > > average: 1.7559818 second > > > > In one word, with the patch applied, the cpu online time during resume > > has decreased by about 6 seconds on a bogus MTRR platform, and decreased > > by about 600ms on a 88 cpus Xeon platform after resumed. > > > > Cc: Len Brown > > Cc: Rafael J. Wysocki > > Cc: Rui Zhang > > Signed-off-by: Chen Yu > > It will be better to combine this with patch [2/3] IMO, because that makes it > clear why the changes in that patch are needed. > > Also you can define the new flag in mtrr/main.c, set it in > arch_enable_nonboot_cpus_begin() and clear it in > arch_enable_nonboot_cpus_end(). It is better to put it into the arch-specific > code as the flag itself is arch-specific. > > Then, of course, you don't need patch [1/3] and all can be done in one patch. > Ok, will rewrite the patch, thanks!