Re: [Qemu-devel] [PATCH] monitor: increase amount of data for monitor to read

[Denis Lunev]

On 7/3/19 9:36 AM, Markus Armbruster wrote:
> Did this fall through the cracks?
>
> Denis Plotnikov <address@hidden> writes:
>
>> Right now QMP and HMP monitors read 1 byte at a time from the socket, which
>> is very inefficient. With 100+ VMs on the host this easily reasults in
>> a lot of unnecessary system calls and CPU usage in the system.
> Yes, reading one byte at a time is awful.  But QMP is control plane; I
> didn't expect it to impact system performance.  How are you using QMP?
> Just curious, not actually opposed to improving QMP efficiency.
500 VMs on a host, each 30 seconds libvirts executes AFAIR 3-5 commands
with default settings. This results in at least some load. It is not very
significant, but it is noticeable.

This reduces idle CPU consumption around 1-2% observable via top, which is
not that small amount.

Den