Messages in this thread | | | Date | Wed, 1 Apr 2015 11:59:35 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent |
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On 2015/03/30 18:58, Gu Zheng wrote: > Hi Kame-san, > > On 03/27/2015 12:31 AM, Kamezawa Hiroyuki wrote: > >> 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 ? > > I use the big array here to keep the same format with the existed ones: > int apic_version[MAX_LOCAL_APIC]; > > s16 __apicid_to_node[MAX_LOCAL_APIC] = { > [0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE > }; > Or we should also say "NO" to them?
This will not survive when someone try to enlarge MAX_LOCAL_APIC for introdcing new cpu model because x2apic is 32bit by definition.
Please create long surviving infrastructure.
Thanks, -Kame
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