From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751414AbbCZFNg (ORCPT ); Thu, 26 Mar 2015 01:13:36 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:45650 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750790AbbCZFNe (ORCPT ); Thu, 26 Mar 2015 01:13:34 -0400 X-IronPort-AV: E=Sophos;i="5.04,848,1406563200"; d="scan'208";a="89579865" Message-ID: <55139128.2050603@cn.fujitsu.com> Date: Thu, 26 Mar 2015 12:55:04 +0800 From: Gu Zheng User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1 MIME-Version: 1.0 To: Kamezawa Hiroyuki CC: , , , , , Subject: Re: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent References: <1427336275-32066-1-git-send-email-guz.fnst@cn.fujitsu.com> <1427336275-32066-2-git-send-email-guz.fnst@cn.fujitsu.com> <55137ADF.7070703@jp.fujitsu.com> In-Reply-To: <55137ADF.7070703@jp.fujitsu.com> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.100] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kame-san, On 03/26/2015 11:19 AM, Kamezawa Hiroyuki wrote: > On 2015/03/26 11:17, Gu Zheng wrote: >> Previously, we build the apicid <--> cpuid mapping when the cpu is present, but >> the relationship will be changed if the cpu/node hotplug happenned, because we >> always choose the first free cpuid for the hot added cpu (whether it is new-add >> or re-add), so this the cpuid <--> node mapping changed if node hot plug >> occurred, and it causes the wq sub-system allocation failture: >> == >> SLUB: Unable to allocate memory on node 2 (gfp=0x80d0) >> cache: kmalloc-192, object size: 192, buffer size: 192, default >> order: >> 1, min order: 0 >> node 0: slabs: 6172, objs: 259224, free: 245741 >> node 1: slabs: 3261, objs: 136962, free: 127656 >> == >> So here we build the persistent [lapic id] <--> cpuid mapping when the cpu first >> present, and never change it. >> >> Suggested-by: KAMEZAWA Hiroyuki >> Signed-off-by: Gu Zheng >> --- >> arch/x86/kernel/apic/apic.c | 31 ++++++++++++++++++++++++++++++- >> 1 files changed, 30 insertions(+), 1 deletions(-) >> >> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c >> index ad3639a..d539ebc 100644 >> --- a/arch/x86/kernel/apic/apic.c >> +++ b/arch/x86/kernel/apic/apic.c >> @@ -2038,6 +2038,30 @@ void disconnect_bsp_APIC(int virt_wire_setup) >> apic_write(APIC_LVT1, value); >> } >> >> +/* >> + * Logic cpu number(cpuid) to local APIC id persistent mappings. >> + * Do not clear the mapping even if cpu hot removed. >> + * */ >> +static int apicid_to_x86_cpu[MAX_LOCAL_APIC] = { >> + [0 ... MAX_LOCAL_APIC - 1] = -1, >> +}; > > > This patch cannot handle x2apic, which is 32bit. IMO, if the apicid is too big (larger than MAX_LOCAL_APIC), we will skip generating a logic cpu number for it, so it seems no problem here. > > As far as I understand, it depends on CPU's spec and the newest cpu has 9bit apicid, at least. > > But you can't create inifinit array. > > If you can't allocate the array dynamically, How about adding > > static int cpuid_to_apicid[MAX_CPU] = {} > > or using idr library ? (please see lib/idr.c) > > I guess you can update this map after boot(after mm initialization) > and make use of idr library. > > About this patch, Nack. > > -Kame > > > >> + >> +/* >> + * Internal cpu id bits, set the bit once cpu present, and never clear it. >> + * */ >> +static cpumask_t cpuid_mask = CPU_MASK_NONE; >> + >> +static int get_cpuid(int apicid) >> +{ >> + int cpuid; >> + >> + cpuid = apicid_to_x86_cpu[apicid]; >> + if (cpuid == -1) >> + cpuid = cpumask_next_zero(-1, &cpuid_mask); >> + >> + return cpuid; >> +} >> + >> int generic_processor_info(int apicid, int version) >> { >> int cpu, max = nr_cpu_ids; >> @@ -2115,7 +2139,10 @@ int generic_processor_info(int apicid, int version) >> */ >> cpu = 0; >> } else >> - cpu = cpumask_next_zero(-1, cpu_present_mask); >> + cpu = get_cpuid(apicid); >> + >> + /* Store the mapping */ >> + apicid_to_x86_cpu[apicid] = cpu; >> >> /* >> * Validate version >> @@ -2144,6 +2171,8 @@ int generic_processor_info(int apicid, int version) >> early_per_cpu(x86_cpu_to_logical_apicid, cpu) = >> apic->x86_32_early_logical_apicid(cpu); >> #endif >> + /* Mark this cpu id as uesed (already mapping a local apic id) */ >> + cpumask_set_cpu(cpu, &cpuid_mask); >> set_cpu_possible(cpu, true); >> set_cpu_present(cpu, true); >> >> > > > . >