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Date: Thu, 3 Mar 2016 09:49:32 +0800 From: Zhu Guihua <zhugh.fnst@...fujitsu.com> To: <cl@...ux.com>, <tj@...nel.org>, <mika.j.penttila@...il.com>, <mingo@...hat.com>, <akpm@...ux-foundation.org>, <rjw@...ysocki.net>, <hpa@...or.com>, <yasu.isimatu@...il.com>, <isimatu.yasuaki@...fujitsu.com>, <kamezawa.hiroyu@...fujitsu.com>, <izumi.taku@...fujitsu.com>, <gongzhaogang@...pur.com>, <len.brown@...el.com>, <lenb@...nel.org>, <tglx@...utronix.de>, <chen.tang@...ystack.cn> CC: <x86@...nel.org>, <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org> Subject: Re: [RESEND PATCH v5 0/5] Make cpuid <-> nodeid mapping persistent Hi Thomas, Ingo, hpa, Would you please help to review the X86 part of this patch-set ? Thanks, Zhu On 03/03/2016 09:42 AM, Zhu Guihua wrote: > [Problem] > > cpuid <-> nodeid mapping is firstly established at boot time. And workqueue caches > the mapping in wq_numa_possible_cpumask in wq_numa_init() at boot time. > > When doing node online/offline, cpuid <-> nodeid mapping is established/destroyed, > which means, cpuid <-> nodeid mapping will change if node hotplug happens. But > workqueue does not update wq_numa_possible_cpumask. > > So here is the problem: > > Assume we have the following cpuid <-> nodeid in the beginning: > > Node | CPU > ------------------------ > node 0 | 0-14, 60-74 > node 1 | 15-29, 75-89 > node 2 | 30-44, 90-104 > node 3 | 45-59, 105-119 > > and we hot-remove node2 and node3, it becomes: > > Node | CPU > ------------------------ > node 0 | 0-14, 60-74 > node 1 | 15-29, 75-89 > > and we hot-add node4 and node5, it becomes: > > Node | CPU > ------------------------ > node 0 | 0-14, 60-74 > node 1 | 15-29, 75-89 > node 4 | 30-59 > node 5 | 90-119 > > But in wq_numa_possible_cpumask, cpu30 is still mapped to node2, and the like. > > When a pool workqueue is initialized, if its cpumask belongs to a node, its > pool->node will be mapped to that node. And memory used by this workqueue will > also be allocated on that node. > > static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs){ > ... > /* if cpumask is contained inside a NUMA node, we belong to that node */ > if (wq_numa_enabled) { > for_each_node(node) { > if (cpumask_subset(pool->attrs->cpumask, > wq_numa_possible_cpumask[node])) { > pool->node = node; > break; > } > } > } > > Since wq_numa_possible_cpumask is not updated, it could be mapped to an offline node, > which will lead to memory allocation failure: > > 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 > > It happens here: > > create_worker(struct worker_pool *pool) > |--> worker = alloc_worker(pool->node); > > static struct worker *alloc_worker(int node) > { > struct worker *worker; > > worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); --> Here, useing the wrong node. > > ...... > > return worker; > } > > > [Solution] > > There are four mappings in the kernel: > 1. nodeid (logical node id) <-> pxm > 2. apicid (physical cpu id) <-> nodeid > 3. cpuid (logical cpu id) <-> apicid > 4. cpuid (logical cpu id) <-> nodeid > > 1. pxm (proximity domain) is provided by ACPI firmware in SRAT, and nodeid <-> pxm > mapping is setup at boot time. This mapping is persistent, won't change. > > 2. apicid <-> nodeid mapping is setup using info in 1. The mapping is setup at boot > time and CPU hotadd time, and cleared at CPU hotremove time. This mapping is also > persistent. > > 3. cpuid <-> apicid mapping is setup at boot time and CPU hotadd time. cpuid is > allocated, lower ids first, and released at CPU hotremove time, reused for other > hotadded CPUs. So this mapping is not persistent. > > 4. cpuid <-> nodeid mapping is also setup at boot time and CPU hotadd time, and > cleared at CPU hotremove time. As a result of 3, this mapping is not persistent. > > To fix this problem, we establish cpuid <-> nodeid mapping for all the possible > cpus at boot time, and make it persistent. And according to init_cpu_to_node(), > cpuid <-> nodeid mapping is based on apicid <-> nodeid mapping and cpuid <-> apicid > mapping. So the key point is obtaining all cpus' apicid. > > apicid can be obtained by _MAT (Multiple APIC Table Entry) method or found in > MADT (Multiple APIC Description Table). So we finish the job in the following steps: > > 1. Enable apic registeration flow to handle both enabled and disabled cpus. > This is done by introducing an extra parameter to generic_processor_info to let the > caller control if disabled cpus are ignored. > > 2. Introduce a new array storing all possible cpuid <-> apicid mapping. And also modify > the way cpuid is calculated. Establish all possible cpuid <-> apicid mapping when > registering local apic. Store the mapping in this array. > > 3. Enable _MAT and MADT relative apis to return non-presnet or disabled cpus' apicid. > This is also done by introducing an extra parameter to these apis to let the caller > control if disabled cpus are ignored. > > 4. Establish all possible cpuid <-> nodeid mapping. > This is done via an additional acpi namespace walk for processors. > > > For previous discussion, please refer to: > https://lkml.org/lkml/2015/2/27/145 > https://lkml.org/lkml/2015/3/25/989 > https://lkml.org/lkml/2015/5/14/244 > https://lkml.org/lkml/2015/7/7/200 > https://lkml.org/lkml/2015/9/27/209 > > Change log v4 -> v5: > 1. Remove useless code in patch 1. > 2. Small improvement of commit message. > > Change log v3 -> v4: > 1. Fix the kernel panic at boot time. The cause is that I tried to build zonelists > before per cpu areas were initialized. > > Change log v2 -> v3: > 1. Online memory-less nodes at boot time to map cpus of memory-less nodes. > 2. Build zonelists for memory-less nodes so that memory allocator will fall > back to proper nodes automatically. > > Change log v1 -> v2: > 1. Split code movement and actual changes. Add patch 1. > 2. Synchronize best near online node record when node hotplug happens. In patch 2. > 3. Fix some comment. > > Gu Zheng (4): > x86, acpi, cpu-hotplug: Enable acpi to register all possible cpus at > boot time. > x86, acpi, cpu-hotplug: Introduce cpuid_to_apicid[] array to store > persistent cpuid <-> apicid mapping. > x86, acpi, cpu-hotplug: Enable MADT APIs to return disabled apicid. > x86, acpi, cpu-hotplug: Set persistent cpuid <-> nodeid mapping when > booting. > > Tang Chen (1): > x86, memhp, numa: Online memory-less nodes at boot time. > > arch/ia64/kernel/acpi.c | 2 +- > arch/x86/include/asm/mpspec.h | 1 + > arch/x86/kernel/acpi/boot.c | 8 ++- > arch/x86/kernel/apic/apic.c | 85 +++++++++++++++++++++++++---- > arch/x86/mm/numa.c | 27 +++++----- > drivers/acpi/acpi_processor.c | 5 +- > drivers/acpi/bus.c | 3 ++ > drivers/acpi/processor_core.c | 122 ++++++++++++++++++++++++++++++++++-------- > include/linux/acpi.h | 2 + > 9 files changed, 204 insertions(+), 51 deletions(-) >
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