[PATCH v2 2/2] drm/i915/gvt: Update time slice more frequently

[Gong, Zhipeng]

> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Tuesday, April 3, 2018 2:36 PM
> 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 2/2] drm/i915/gvt: Update time slice more frequently
> 
> On 2018.04.03 09:24:25 +0800, Zhipeng Gong wrote:
> > When there is only one vGPU in GVT-g and it submits workloads
> > continuously, it will not be scheduled out, vgpu_update_timeslice
> > is not called and its sched_in_time is not updated in a long time,
> > which can be several seconds or longer.
> > Once GVT-g pauses to submit workload for this vGPU due to heavy
> > host CPU workload, this vGPU get scheduled out and
> > vgpu_update_timeslice is called, its left_ts will be subtract
> > by a big value from sched_out_time - sched_in_time.
> > When GVT-g is going to submit workload for this vGPU again,
> > it will not be scheduled in until gvt_balance_timeslice reaches
> > stage 0 and reset its left_ts, which introduces several
> > hunderand milliseconds latency.
> >
> > This patch updates time slice in every ms to update sched_in_time
> > timely.
> >
> > v2: revise commit message
> >
> > 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 | 26 ++++++++++++++------------
> >  1 file changed, 14 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c
> b/drivers/gpu/drm/i915/gvt/sched_policy.c
> > index a8b544a..0169e3b 100644
> > --- a/drivers/gpu/drm/i915/gvt/sched_policy.c
> > +++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
> > @@ -53,7 +53,6 @@ struct vgpu_sched_data {
> >  	bool active;
> >
> >  	ktime_t sched_in_time;
> > -	ktime_t sched_out_time;
> >  	ktime_t sched_time;
> >  	ktime_t left_ts;
> >  	ktime_t allocated_ts;
> > @@ -69,15 +68,19 @@ struct gvt_sched_data {
> >  	ktime_t expire_time;
> >  };
> >
> > -static void vgpu_update_timeslice(struct intel_vgpu *pre_vgpu)
> > +static void vgpu_update_timeslice(struct intel_vgpu *vgpu, ktime_t cur_time)
> >  {
> >  	ktime_t delta_ts;
> > -	struct vgpu_sched_data *vgpu_data = pre_vgpu->sched_data;
> > +	struct vgpu_sched_data *vgpu_data;
> >
> > -	delta_ts = vgpu_data->sched_out_time - vgpu_data->sched_in_time;
> > +	if (vgpu == NULL || vgpu == vgpu->gvt->idle_vgpu)
> > +		return;
> 
> Use if (!vgpu || ...)

ok

> >
> > -	vgpu_data->sched_time += delta_ts;
> > -	vgpu_data->left_ts -= delta_ts;
> > +	vgpu_data = vgpu->sched_data;
> > +	delta_ts = ktime_sub(cur_time, vgpu_data->sched_in_time);
> > +	vgpu_data->sched_time = ktime_add(vgpu_data->sched_time, delta_ts);
> > +	vgpu_data->left_ts = ktime_sub(vgpu_data->left_ts, delta_ts);
> > +	vgpu_data->sched_in_time = cur_time;
> >  }
> >
> >  #define GVT_TS_BALANCE_PERIOD_MS 100
> > @@ -151,11 +154,7 @@ static void try_to_schedule_next_vgpu(struct
> intel_gvt *gvt)
> >  	}
> >
> >  	cur_time = ktime_get();
> > -	if (scheduler->current_vgpu) {
> > -		vgpu_data = scheduler->current_vgpu->sched_data;
> > -		vgpu_data->sched_out_time = cur_time;
> > -		vgpu_update_timeslice(scheduler->current_vgpu);
> > -	}
> > +	vgpu_update_timeslice(scheduler->current_vgpu, cur_time);
> >  	vgpu_data = scheduler->next_vgpu->sched_data;
> >  	vgpu_data->sched_in_time = cur_time;
> 
> Can simply put ktime_get() into vgpu_update_timeslice(), and above lines can be
> removed as well.
> 

cur_time is needed to update next vgpu's vgpu_data->sched_in_time, it can not 
be removed. 

> >
> > @@ -227,12 +226,14 @@ 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;
> > +	ktime_t cur_time;
> >
> >  	mutex_lock(&gvt->lock);
> > +	cur_time = ktime_get();
> >
> >  	if (test_and_clear_bit(INTEL_GVT_REQUEST_SCHED,
> >  				(void *)&gvt->service_request)) {
> > -		if (ktime_get() >= sched_data->expire_time) {
> > +		if (cur_time >= sched_data->expire_time) {
> >  			gvt_balance_timeslice(sched_data);
> >  			sched_data->expire_time = ktime_add_ms(
> >  				sched_data->expire_time,
> > @@ -241,6 +242,7 @@ void intel_gvt_schedule(struct intel_gvt *gvt)
> >  	}
> >  	clear_bit(INTEL_GVT_REQUEST_EVENT_SCHED, (void *)&gvt-
> >service_request);
> >
> > +	vgpu_update_timeslice(gvt->scheduler.current_vgpu, cur_time);
> >  	tbs_sched_func(sched_data);
> >
> >  	mutex_unlock(&gvt->lock);
> > --
> > 2.7.4
> >
> > _______________________________________________
> > intel-gvt-dev mailing list
> > intel-gvt-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
> 
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