[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 2:11 PM
> To: Gong, Zhipeng <zhipeng.gong at intel.com>
> Cc: He, Min <min.he at intel.com>; intel-gvt-dev at lists.freedesktop.org
> Subject: Re: [PATCH v2 1/2] drm/i915/gvt: Use real time to do timer check
> 
> On 2018.04.03 04:58:10 +0000, Gong, Zhipeng wrote:
> > > 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.
> 
> Then that might simply use your current form, and to update expire_time
> shouldn't use
> ktime_add_ms(ktime_get(), expire)?
> 

You are right, I will correct it. 

> > 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?
> >
> 
> ok.
> 
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