Re: [RFC PATCH] iothread: add set_iothread_poll_* commands

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Oct 22, 2019 at 04:12:03PM +0800, yezhenyu (A) wrote:
> Since qemu2.9, QEMU added three AioContext poll parameters to struct
> IOThread: poll_max_ns, poll_grow and poll_shrink. These properties are
> used to control iothread polling time.
> 
> However, there isn't properly hmp commands to adjust them when the VM is
> alive. It's useful to adjust them online when observing the impact of
> different property value on performance.
> 
> This patch add three hmp commands to adjust iothread poll-* properties
> for special iothread:
> 
> set_iothread_poll_max_ns: set the maximum polling time in ns;
> set_iothread_poll_grow: set how many ns will be added to polling time;
> set_iothread_poll_shrink: set how many ns will be removed from polling
> time.
> 
> Signed-off-by: Zhenyu Ye <yezhenyu2@huawei.com>
> ---
> hmp-commands.hx | 42 ++++++++++++++++++++
> hmp.c | 30 +++++++++++++++
> hmp.h | 3 ++
> include/sysemu/iothread.h | 6 +++
> iothread.c | 80 +++++++++++++++++++++++++++++++++++++++
> qapi/misc.json | 23 +++++++++++
> 6 files changed, 184 insertions(+)

poll-max-ns, poll-grow, poll-shrink are properties of IOThread objects.
They can already be modified at runtime using:

  $ qemu -object iothread,id=iothread1
  (qemu) qom-set /objects/iothread1 poll-max-ns 100000

I think there is no need for a patch.

Stefan

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