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SubjectRe: [PATCH v2 5/6] KVM: sort memslots by its size and use line search
On 11/20/2011 07:26 PM, Avi Kivity wrote:

> On 11/18/2011 11:19 AM, Xiao Guangrong wrote:
>> Sort memslots base on its size and use line search to find it, so the larger
>> memslots have better fit
>>
>> The idea is from Avi
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
>> ---
>> include/linux/kvm_host.h | 22 +++++++++---
>> virt/kvm/kvm_main.c | 82 ++++++++++++++++++++++++++++++++-------------
>> 2 files changed, 75 insertions(+), 29 deletions(-)
>>
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index a0e4d63..83b396a 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -230,8 +230,12 @@ struct kvm_irq_routing_table {};
>> #define KVM_MEM_SLOTS_NUM (KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
>> #endif
>>
>> +/*
>> + * Note:
>> + * memslots are not sorted by id anymore, please use id_to_memslot()
>> + * to get the memslot by its id.
>> + */
>> struct kvm_memslots {
>> - int nmemslots;
>> u64 generation;
>> struct kvm_memory_slot memslots[KVM_MEM_SLOTS_NUM];
>> };
>> @@ -307,9 +311,10 @@ static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
>> (vcpup = kvm_get_vcpu(kvm, idx)) != NULL; \
>> idx++)
>>
>> -#define kvm_for_each_memslot(slots, memslot, i) \
>> - for (i = 0; i < (slots)->nmemslots && \
>> - ({ memslot = &(slots)->memslots[i]; 1; }); i++)
>> +#define kvm_for_each_memslot(slots, memslot, i) \
>> + for (i = 0; i < KVM_MEM_SLOTS_NUM && \
>> + ({ memslot = &(slots)->memslots[i]; 1; }) && \
>> + memslot->npages != 0; i++)
>
> You might allocate an always-empty memslot at the end and simplify the
> termination condition.
>


The slots are sorted by its size, all empty slots are at the end of the array,
so we can simplify break the loop if meet a empty slot.



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