[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd |
Date: |
Wed, 14 Mar 2012 09:59:09 +0000 |
On Wed, Mar 14, 2012 at 9:22 AM, Avi Kivity <address@hidden> wrote:
> On 03/13/2012 12:42 PM, Amos Kong wrote:
>> Boot up guest with 232 virtio-blk disk, qemu will abort for fail to
>> allocate ioeventfd. This patchset changes kvm_has_many_ioeventfds(),
>> and check if available ioeventfd exists. If not, virtio-pci will
>> fallback to userspace, and don't use ioeventfd for io notification.
>
> How about an alternative way of solving this, within the memory core:
> trap those writes in qemu and write to the ioeventfd yourself. This way
> ioeventfds work even without kvm:
>
>
> core: create eventfd
> core: install handler for memory address that writes to ioeventfd
> kvm (optional): install kernel handler for ioeventfd
>
> even if the third step fails, the ioeventfd still works, it's just slower.
That approach will penalize guests with large numbers of disks - they
see an extra switch to vcpu thread instead of kvm.ko -> iothread. It
seems okay provided we can solve the limit in the kernel once and for
all by introducing a more dynamic data structure for in-kernel
devices. That way future kernels will never hit an arbitrary limit
below their file descriptor rlimit.
Is there some reason why kvm.ko must use a fixed size array? Would it
be possible to use a tree (maybe with a cache for recent lookups)?
Stefan
- Re: [Qemu-devel] [PATCH 1/2] return available ioeventfds count in kvm_has_many_ioeventfds(), (continued)
Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Amos Kong, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Amos Kong, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Amos Kong, 2012/03/13
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/14
Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Avi Kivity, 2012/03/14
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Avi Kivity, 2012/03/14
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/14
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Avi Kivity, 2012/03/14
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/14
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Amos Kong, 2012/03/16
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Stefan Hajnoczi, 2012/03/19
- Re: [Qemu-devel] [PATCH 0/2] virtio-pci: fix abort when fail to allocate ioeventfd, Avi Kivity, 2012/03/19