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Re: [RFC] hw/nvme: Use irqfd to send interrupts
From: |
Klaus Jensen |
Subject: |
Re: [RFC] hw/nvme: Use irqfd to send interrupts |
Date: |
Thu, 14 Jul 2022 06:18:16 +0200 |
On Jul 12 14:26, Klaus Jensen wrote:
> On Jul 9 12:35, Jinhao Fan wrote:
> > Use irqfd to directly notify KVM to inject interrupts. This is done by
> > registering a virtual IRQ(virq) in KVM and associate the virq with an
> > irqfd, so that KVM can directly inject the interrupt when it receives
> > notification from the irqfd. This approach is supposed to improve
> > performance because it bypasses QEMU's MSI interrupt emulation logic.
> >
> > However, I did not see an obvious improvement of the emulation KIOPS:
> >
> > QD 1 4 16 64
> > QEMU 38 123 210 329
> > irqfd 40 129 219 328
> >
> > I found this problem quite hard to diagnose since irqfd's workflow
> > involves both QEMU and the in-kernel KVM.
> >
> > Could you help me figure out the following questions:
> >
> > 1. How much performance improvement can I expect from using irqfd?
>
> This is a level of QEMU/KVM that I am by no means an expert on and I
> would have to let the broader QEMU community comment on this.
>
In any case, I'm wary about adding this level of kvm-dependence in the
device. This wont work on non-kvm platforms any more.
I think you should put irqfd on hold and focus on iothreads :)
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- [RFC] hw/nvme: Use irqfd to send interrupts, Jinhao Fan, 2022/07/09
- Re: [RFC] hw/nvme: Use irqfd to send interrupts, Klaus Jensen, 2022/07/12
- Re: [RFC] hw/nvme: Use irqfd to send interrupts,
Klaus Jensen <=
- Re: [RFC] hw/nvme: Use irqfd to send interrupts, Jinhao Fan, 2022/07/20
- Re: [RFC] hw/nvme: Use irqfd to send interrupts, Stefan Hajnoczi, 2022/07/20
- Re: [RFC] hw/nvme: Use irqfd to send interrupts, Klaus Jensen, 2022/07/27
- Re: [RFC] hw/nvme: Use irqfd to send interrupts, Stefan Hajnoczi, 2022/07/27