Re: [PATCH] hw/virtio: Add ioeventfd option for balloon

[David Hildenbrand <david@redhat.com>]

On 04.01.24 08:15, 沈哲赟 wrote:
> Traditional mmio in balloon makes Qemu do balloon inflation in the same
> thread as vcpu thread. In a CPU overcommitment scenario, host may run
> more than one vcpu threads on one host CPU, which makes
> madvise_dontneed_free() wait for a long time due to the function
> cond_resched() at host side.
> 
> If using SEV/ES and the kernel provided by AMD, the overhead will
> become even much larger.(From 90s to 1400s when reclaming 4GB)

I recall that encrypted VMs etc are not compatible with ballooning. Are 
there other (i.e., guest kernel) changes required for this setup to 
work? ("provided by AMD")

> 
> With ioeventfd, the thread for host to do balloon inflation will
> be separated from the VCPU thread, leading to better performance
> for the whole process of balloon inflation.(1400s to 263s
> in SEV CPU overcommitment scenario)
> 
> As a para-virtual solution, balloon serves for host so the process
> of inflation in host needs to run on a host iothread instead of a guest
> VCPU thread.
> 
> Signed-off-by: Zheyun Shen <szy0127@sjtu.edu.cn>

If this a resend i.e., v2, please indicate changes below the "---" and 
use versions like "PATCH v2".

https://lkml.kernel.org/r/https://lkml.kernel.org/r/20231212075058.710918-1-szy0127@sjtu.edu.cn

-- 
Cheers,

David / dhildenb