[PATCH v2 1/2] drm/i915/gvt: Use real time to do timer check

[Gong, Zhipeng]

> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Tuesday, April 3, 2018 10:36 AM
> To: Gong, Zhipeng <zhipeng.gong at intel.com>
> Cc: intel-gvt-dev at lists.freedesktop.org; He, Min <min.he at intel.com>
> Subject: Re: [PATCH v2 1/2] drm/i915/gvt: Use real time to do timer check
> 
> On 2018.04.03 09:24:24 +0800, Zhipeng Gong wrote:
> > intel_gvt_schedule check timer through a counter and is supposed
> > to wake up to increase the counter every ms.
> > In a system with heavy workload, gvt_service_thread can not get
> > a chance to run right after wake up and will be delayed several
> > milliseconds. As a result, one hundred counter interval means
> > several hundred milliseconds in real time.
> >
> > This patch use real time instead of counter to do timer check.
> >
> > v2: remove static variable. (Zhenyu)
> >
> > Signed-off-by: Zhipeng Gong <zhipeng.gong at intel.com>
> > Cc: Zhenyu Wang <zhenyuw at linux.intel.com>
> > Cc: Min He <min.he at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gvt/sched_policy.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c
> b/drivers/gpu/drm/i915/gvt/sched_policy.c
> > index 75b7bc7..a8b544a 100644
> > --- a/drivers/gpu/drm/i915/gvt/sched_policy.c
> > +++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
> > @@ -66,6 +66,7 @@ struct gvt_sched_data {
> >  	struct hrtimer timer;
> >  	unsigned long period;
> >  	struct list_head lru_runq_head;
> > +	ktime_t expire_time;
> >  };
> >
> >  static void vgpu_update_timeslice(struct intel_vgpu *pre_vgpu)
> > @@ -226,14 +227,17 @@ static void tbs_sched_func(struct gvt_sched_data
> *sched_data)
> >  void intel_gvt_schedule(struct intel_gvt *gvt)
> >  {
> >  	struct gvt_sched_data *sched_data = gvt->scheduler.sched_data;
> > -	static uint64_t timer_check;
> >
> >  	mutex_lock(&gvt->lock);
> >
> >  	if (test_and_clear_bit(INTEL_GVT_REQUEST_SCHED,
> >  				(void *)&gvt->service_request)) {
> > -		if (!(timer_check++ % GVT_TS_BALANCE_PERIOD_MS))
> > +		if (ktime_get() >= sched_data->expire_time) {
> >  			gvt_balance_timeslice(sched_data);
> > +			sched_data->expire_time = ktime_add_ms(
> > +				sched_data->expire_time,
> > +				GVT_TS_BALANCE_PERIOD_MS);
> > +		}
> >  	}
> 
> Use if ktime_after(ktime_get(), expire_time) instead and should initialize
> expire_time
> or we currently just kick in first schedule?
>

ktime_after will introduce 1ms gap if intel_gvt_schedule is called right at 100ms.
I will use !ktime_before instead.
Currently expire_time is inited to 0 by kzalloc in tbs_sched_init, and gvt_balance_timeslice 
is called in first schedule. Is it ok to keep this behavior?

> >  	clear_bit(INTEL_GVT_REQUEST_EVENT_SCHED, (void *)&gvt-
> >service_request);
> >
> > --
> > 2.7.4
> >
> 
> --
> Open Source Technology Center, Intel ltd.
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