[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH (resend, rebase) 3/3] virtio-serial: Enable ioev
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH (resend, rebase) 3/3] virtio-serial: Enable ioeventfd |
Date: |
Mon, 28 Feb 2011 15:28:49 +0000 |
On Mon, Feb 28, 2011 at 11:12 AM, Amit Shah <address@hidden> wrote:
> Enable ioeventfd for virtio-serial devices by default. Commit
> 25db9ebe15125deb32958c6df74996f745edf1f9 lists the benefits of using
> ioeventfd.
>
> Copying a file from guest to host over a virtio-serial channel didn't
> show much difference in time or io_exit rate.
The cost of enabling ioeventfd is one eventfd file descriptor and KVM
in-kernel device slot per virtqueue. The current maximum number per
VM is 200, this is a kernel limit in
include/linux/kvm_host.h:NR_IOBUS_DEVS.
Do you really want to use ioeventfd for virtio-serial? Perhaps this
is more useful for high-frequency device interfaces.
Stefan
- [Qemu-devel] [PULL (resend, rebase) 0/3] virtio-serial fixes, ioeventfd support, Amit Shah, 2011/02/28
- [Qemu-devel] [PATCH (resend, rebase) 1/3] virtio-serial: Use a struct to pass config information from proxy, Amit Shah, 2011/02/28
- [Qemu-devel] [PATCH (resend, rebase) 2/3] virtio-serial: Disallow generic ports at id 0, Amit Shah, 2011/02/28
- [Qemu-devel] [PATCH (resend, rebase) 3/3] virtio-serial: Enable ioeventfd, Amit Shah, 2011/02/28
- Re: [Qemu-devel] [PATCH (resend, rebase) 3/3] virtio-serial: Enable ioeventfd,
Stefan Hajnoczi <=