vsync-app 不稳定导致抖动
问题描述：跟对比机器对比uc 浏览器新闻页滑动场景，出现抖动
1、trace 看是没有丢帧，对比看送帧buffer 给到 SF 步调不够一致，从间隔较大的两个 送帧buffer看，发现vsync-app 时间比正常的要长3ms 左右，vsync-app 不稳定。
从出现 vsync-app 不稳定帧，到下一个vsync-app ，看TimerDispatch 唤醒关系，已知的有两种情况：
1、 crtc_commit =》唤醒TimerDispatch
截图TimerDispatch 唤醒：
crtc_commit:161 992-992 ( 992) [001] d.h. 345.231339: softirq_raise: vec=1 [action=TIMER]
crtc_commit:161 992-992 ( 992) [001] d.h. 345.231341: softirq_raise: vec=9 [action=RCU]
crtc_commit:161 992-992 ( 992) [001] d.h5 345.231371: sched_waking: comm=TimerDispatch pid=2689 prio=97 target_cpu=001
crtc_commit:161 992-992 ( 992) [001] d.h6 345.231401: ipi_raise: target_mask=00000000,00000004 (Rescheduling interrupts)
<idle>-0 (-------) [002] dn.1 345.231406: cpu_idle: state=4294967295 cpu_id=2
crtc_commit:161 992-992 ( 992) [001] d.h6 345.231406: sched_wakeup: comm=TimerDispatch pid=2689 prio=97 target_cpu=002
crtc_commit:161 992-992 ( 992) [001] d.h5 345.231371: sched_waking: comm=TimerDispatch pid=2689 prio=97 target_cpu=001
crtc_commit:161 992-992 ( 992) [001] d.h5 345.231371: sched_waking: comm=TimerDispatch pid=2689 prio=97 target_cpu=001
crtc_commit:161 992-992 ( 992) [001] d.H. 345.231420: irq_handler_entry: irq=211 name=kgsl_3d0_irq
<idle>-0 (-------) [002] d..2 345.231426: sched_switch: prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
截图唤醒及紧接着2 处 TimerDispatch 唤醒
crtc_commit:161 992-992 ( 992) [001] d.H. 345.231420: irq_handler_entry: irq=211 name=kgsl_3d0_irq
<idle>-0 (-------) [002] d..2 345.231426: sched_switch: prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
VizCompositor 9171-9171 ( 8471) [000] d..2 345.233571: sched_waking: comm=Compositor pid=8886 prio=116 target_cpu=005
<idle>-0 (-------) [003] d..2 345.233574: sched_switch: prev_comm=swapper/3 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
crtc_commit:161 992-992 ( 992) [000] .... 345.239369: sde_evtlog: 992|sde_encoder_phys_cmd_prepare_for_kickoff:1574|0x39|0x0|0x1|0x0|0x2|0x0|0x0|0x0|0x0|0x0|0x0|0x0|0x0|0x0|0x0
<idle>-0 (-------) [002] d..2 345.239369: sched_switch: prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
2、 swapper =》唤醒TimerDispatch
这一次唤醒关系
Chrome_ChildIOT 8871-8871 ( 8471) [000] d..6 345.099259: sched_wakeup: comm=VizCompositor pid=9171 prio=116 target_cpu=003
<idle>-0 (-------) [001] dnh1 345.099260: softirq_raise: vec=1 [action=TIMER]
<idle>-0 (-------) [002] d..1 345.099260: cpu_idle: state=0 cpu_id=2
<idle>-0 (-------) [001] dnh1 345.099263: softirq_raise: vec=9 [action=RCU]
<idle>-0 (-------) [003] dn.1 345.099265: irq_handler_entry: irq=1 name=IPI
<idle>-0 (-------) [003] dn.1 345.099266: ipi_entry: (Rescheduling interrupts)
<idle>-0 (-------) [003] dN.1 345.099268: ipi_exit: (Rescheduling interrupts)
<idle>-0 (-------) [003] dN.1 345.099270: irq_handler_exit: irq=1 ret=handled
<idle>-0 (-------) [003] d..2 345.099284: sched_switch: prev_comm=swapper/3 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=VizCompositor next_pid=9171 next_prio=116
<idle>-0 (-------) [001] dnh6 345.099290: sched_waking: comm=TimerDispatch pid=s prio=97 target_cpu=001
Chrome_ChildIOT 8871-8871 ( 8471) [000] d..2 345.099306: sched_waking: comm=uhk_traffic pid=8954 prio=120 target_cpu=002
<idle>-0 (-------) [001] dnh7 345.099317: ipi_raise: target_mask=00000000,00000004 (Rescheduling interrupts)
<idle>-0 (-------) [001] dnh7 345.099321: sched_wakeup: comm=TimerDispatch pid=w prio=97 target_cpu=002
<idle>-0 (-------) [002] dn.1 345.099321: cpu_idle: state=4294967295 cpu_id=2
<idle>-0 (-------) [002] dn.1 345.099325: irq_handler_entry: irq=1 name=IPI
<idle>-0 (-------) [002] dn.1 345.099327: ipi_entry: (Rescheduling interrupts)
<idle>-0 (-------) [002] dN.1 345.099328: ipi_exit: (Rescheduling interrupts)
<idle>-0 (-------) [002] dN.1 345.099329: irq_handler_exit: irq=1 ret=handled
Chrome_ChildIOT 8871-8871 ( 8471) [000] d..3 345.099330: sched_wakeup: comm=uhk_traffic pid=8954 prio=120 target_cpu=002
<idle>-0 (-------) [001] dnh1 345.099334: irq_handler_exit: irq=11 ret=handled
Chrome_ChildIOT 8871-8871 ( 8471) [000] d..2 345.099336: sched_waking: comm=VizCompositor pid=9171 prio=116 target_cpu=003
<idle>-0 (-------) [002] d..2 345.099339: sched_switch: prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
<idle>-0 (-------) [001] dnH1 345.099347: irq_handler_entry: irq=211 name=kgsl_3d0_irq
<idle>-0 (-------) [001] dnH4 345.099363: sched_waking: comm=kgsl_dispatcher pid=962 prio=49 target_cpu=002
往前一次唤醒vsync-sf 关系
GPU completion 13438-13438 ( 7730) [002] d..2 345.090390: sched_switch: prev_comm=GPU completion prev_pid=13438 prev_prio=110 prev_state=S ==> next_comm=swapper/2 next_pid=0 next_prio=120
<idle>-0 (-------) [002] d..1 345.090410: cpu_idle: state=0 cpu_id=2
<idle>-0 (-------) [001] d..1 345.090413: cpu_idle: state=4294967295 cpu_id=1
<idle>-0 (-------) [001] d.h1 345.090420: irq_handler_entry: irq=11 name=arch_timer
<idle>-0 (-------) [001] d.h6 345.090427: sched_waking: comm=TimerDispatch pid=2689 prio=97 target_cpu=001
<idle>-0 (-------) [001] dNh7 345.090447: sched_wakeup: comm=TimerDispatch pid=2689 prio=97 target_cpu=001
<idle>-0 (-------) [001] d..2 345.090470: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=TimerDispatch next_pid=2689 next_prio=97
1、跟显示关系
vsync-app crtc_commit =》唤醒TimerDispatch 时间太长，可以看得到最后刷新到屏内容延长了，不稳定。
2、vsync-app 不稳定，是由于epoll SF 中 fd 时，由于设置的timer 时间到了，而写fd 内容延迟，导致epoll 延迟从而vsync 不稳定。
