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Date: Wed, 17 May 2017 03:43:39 -0400 (EDT)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] About QEMU BQL and dirty log switch in Migration
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To: "Zhoujian (jay)" <jianjay.zhou@huawei.com>
Cc: Wanpeng Li <kernellwp@gmail.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, yanghongyang <yanghongyang@huawei.com>, quintela@redhat.com, "wangxin (U)" <wangxinxin.wang@huawei.com>, qemu-devel@nongnu.org, "Gonglei (Arei)" <arei.gonglei@huawei.com>, Huangzhichao <huangzhichao@huawei.com>, Zhanghailiang <zhang.zhanghailiang@huawei.com>, "Herongguang (Stephen)" <herongguang.he@huawei.com>, Xiao Guangrong <xiaoguangrong@tencent.com>, "Huangweidong (C)" <weidong.huang@huawei.com>

> Recently, I have tested the performance before migration and after migration failure
> using spec cpu2006 https://www.spec.org/cpu2006/, which is a standard performance
> evaluation tool.
>
> These are the steps:
> ======
>  (1) the version of kmod is 4.4.11(with slightly modified) and the version of
>  qemu is 2.6.0
>     (with slightly modified), the kmod is applied with the following patch
> 
> diff --git a/source/x86/x86.c b/source/x86/x86.c
> index 054a7d3..75a4bb3 100644
> --- a/source/x86/x86.c
> +++ b/source/x86/x86.c
> @@ -8550,8 +8550,10 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>          */
>         if ((change != KVM_MR_DELETE) &&
>                 (old->flags & KVM_MEM_LOG_DIRTY_PAGES) &&
> -               !(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
> -               kvm_mmu_zap_collapsible_sptes(kvm, new);
> +               !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) {
> +               printk(KERN_ERR "zj make KVM_REQ_MMU_RELOAD request\n");
> +               kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
> +       }
>  
>         /*
>          * Set up write protection and/or dirty logging for the new slot.

Try these modifications to the setup:

1) set up 1G hugetlbfs hugepages and use those for the guest's memory

2) test both without and with the above patch.

Thanks,

Paolo