lkml.org 
[lkml]   [2015]   [Mar]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent
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);
>>>
>>>
>>
>>
>> .
>>
>
>




\
 
 \ /
  Last update: 2015-03-26 18:01    [W:0.101 / U:1.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site