On 2017/8/29 20:46, Peter Zijlstra wrote:
On Tue, Aug 29, 2017 at 11:46:41AM +0000, Yang Zhang wrote:
In ttwu_do_wakeup, it will update avg_idle when wakeup from idle. Here
we just reuse this logic to update the poll time. It may be a little
late to update the poll in ttwu_do_wakeup, but the test result shows no
obvious performance gap compare with updating poll in irq handler.
one problem is that idle_stamp only used when using CFS scheduler. But
it is ok since it is the default policy for scheduler and only consider
it should enough.
Signed-off-by: Yang Zhang <yang.zhang.wz@xxxxxxxxx>
Signed-off-by: Quan Xu <quan.xu0@xxxxxxxxx>
Same broken SoB chain, and not a useful word on why you need to adjust
this crap to begin with. What you want that poll duration to be related
to is the cost of a VMEXIT/VMENTER cycle, not however long we happened
to be idle.
So no.
Peter,
I think you are right..
IIUC, the time we happened to be idle may contain a chain of
VMEXIT/VMENTER cycles,
which would be mainly (except the last VMEXIT/VMENTER cycles) for just
idle loops. right?
as you mentioned, poll duration to be related to is the cost of __a__
VMEXIT/VMENTER cycle.
howerver it is very difficult to measure a VMEXIT/VMENTER cycle
accurately from
kvm guest, we could find out an approximate one -- dropping the idle
loops from the
time we happened to be idle.. make sense?
Quan
