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From: "Longpeng (Mike)" <longpeng2@huawei.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Alex Williamson <alex.williamson@redhat.com>
Cc: <qemu-devel@nongnu.org>, <kvm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	"Longpeng(Mike)" <longpeng.mike@gmail.com>,
	Gonglei <arei.gonglei@huawei.com>,
	Huangzhichao <huangzhichao@huawei.com>
Subject: Re: vfio_pin_map_dma cause synchronize_sched wait too long
Date: Mon, 2 Dec 2019 17:42:13 +0800
Message-ID: <561fb205-16be-ae87-9cfe-61e6a3b04dc5@huawei.com> (raw)
In-Reply-To: <34c53520-4144-fe71-528a-8df53e7f4dd1@redhat.com>

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)


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02  9:10 Longpeng (Mike)
2019-12-02  9:31 ` Paolo Bonzini
2019-12-02  9:42   ` Longpeng (Mike) [this message]
2019-12-02 10:06     ` Paolo Bonzini
2019-12-02 10:47       ` Longpeng (Mike)

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