[Bug 199727] CPU freezes in KVM guests during high IO load on host

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=199727

Stefan Hajnoczi (stefanha@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |stefanha@gmail.com

--- Comment #12 from Stefan Hajnoczi (stefanha@gmail.com) ---
Hi,
I contribute to QEMU and have encountered similar issues in the past. QEMU
configuration options that should allow you to avoid this issue and it sounds
like you have found options that work for you.

If io_submit(2) is blocking with aio=native, try aio=io_uring. If that is not
available (older kernels), use aio=threads to work around this particular
problem.

I recommend cache=none. Although cache=writeback can shift the problem around
it doesn't solve it and leaves the VMs open to unpredictable performance
(including I/O stalls like this) due to host memory pressure and host page
cache I/O.

Regarding the original bug report, it's a limitation of that particular QEMU
configuration. I don't think anything will be done about it in the Linux
kernel. Maybe Proxmox can adjust the QEMU configuration to avoid it.

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are watching the assignee of the bug.