Re: vfio_pin_map_dma cause synchronize_sched wait too long

[Longpeng (Mike)]

在 2019/12/2 17:31, Paolo Bonzini 写道:
> On 02/12/19 10:10, Longpeng (Mike) wrote:
>>
>> Suppose there're two VMs: VM1 is bind to node-0 and calling 
>> vfio_pin_map_dma(),
>> VM2 is a migrate incoming VM which bind to node-1. We found the vm_start( 
>> QEMU
>> function) of VM2 will take too long occasionally, the reason is as follow.
> 
> Which part of vfio_pin_map_dma is running?  There is already a

I need more analysis to find which part.

> cond_resched in vfio_iommu_map.  Perhaps you could add one to
> vfio_pin_pages_remote and/or use vfio_pgsize_bitmap to cap the number of
> pages that it returns.

Um ... There's only one running task (qemu-kvm of the VM1) on that CPU, so maybe
the cond_resched() is ineffective ?

> > Paolo
> 
> 
> 


-- 
Regards,
Longpeng(Mike)