Messages in this thread Patch in this message | | | Date | Fri, 27 Mar 2015 01:31:23 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent |
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On 2015/03/26 13:55, Gu Zheng wrote: > 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 <kamezawa.hiroyu@jp.fujitsu.com> >>> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com> >>> --- >>> 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. > you mean MAX_LOCAL_APIC=32768 ? ....isn't it too wasting ?
Anyway, APIC IDs are sparse values. Please use proper structure.
Thanks, -Kame
>> >> 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); >>> >>> >> >> >> . >> > >
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