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carlnues@buffalo.edu 2023-08-25 21:55:24 -04:00
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sections/evaluation.tex
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@ -89,8 +89,8 @@ We evaluate six different CPU policies under different workloads:
(iv) a truncated \schedutil implemented with \systemname,
(v) unmodified \systemname, and
(vi) the \texttt{performance} governor.
We include (ii) and (iii) to compare the general performance of the truncated \schedutil and a general-case $\sim$70\% speed policies when implemented under the existing API with that when implemented using \systemname.
Under default Linux, a specific CPU speed requested gets implemented as the next-highest speed in a preset series of supported speeds in texttt{scaling\_available\_frequencies} in texttt{sysfs}.
We include (ii) and (iii) to compare the general performance of the truncated \schedutil and a common-case $\sim$70\% speed policies when implemented under the existing API with the equivalents implemented using \systemname.
Under default Linux, a specific CPU speed requested gets implemented as the next-highest speed in a preset series of supported speeds in \texttt{scaling\_available\_frequencies} in \texttt{sysfs}.
We follow this behavior with our system.
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@ -104,22 +104,22 @@ The app selects the first hit, starts the video, and waits for 30 seconds.
The specific video was selected to get a predictable high rate of being served random motion video ads at the start.
The \textbf{Spotify} workload starts the app searches for a common musical selection.
It starts the first suggestion and waits for 30 seconds while the audio plays with the app in the foreground.
Lastly, the \textbf{Combined} workload examines the system under additional stress.
Lastly, the \textbf{Combined} workload examines the system under commonplace additional stress.
It runs the original Facebook workload in the foreground while the Spotify app streams audio continuously in the background.
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\subsection{Screen Jank}
\Cref{fig:jank_allapps} show frame drop rates for the four workloads.
\Cref{fig:jank_allapps} shows frame drop rates for the four workloads.
These graphs address the performance aspect of claims (i) and (ii).
On all workloads, \systemname and truncated \schedutil offer nearly identical or notably better performance than regular \schedutil.
The Facebook load under \systemname costs an additional .3\%, or $\sim$.2 frames per second at 60fps.
We argue this does not noticably affect user experience and is more than acceptable given the greater than 10\% energy savings.
The results of the truncated \schedutil policies and of fixedspeed 70\% similar offer significant energy savings at small to zero cost.
The results of the truncated \schedutil policies and of fixedspeed 70\% similarly offer significant energy savings at small to zero cost.
Youtube shows a clear performance win for \systemname compared to the default.
The truncated \schedutil policies and fixed speed 70\% policy also offer improved performance to the default.
Performance under \systemname for both Spotify and the Combined workloads, like that for Facebook, costs .3\% fps compared to the default -- a cost we again argue is very minimal and acceptable.
The truncated \schedutil policies and fixed speed 70\% policy also offer improved sreendrop rates.
Performance under \systemname for both the Spotify and the Combined workloads, like that for Facebook, costs .3\% fps compared to the default -- a cost we again argue is both very minimal and acceptable.
The other non-default policies for both Spotify and Combined also offer either essentially the same or even somewhat better performance than the default.
Particularly, the increased background load of Combined does not change screendrop rate appreciably.
In summary: \systemname, with a considerably simpler policy mechanism, offers essentially the same performance, measured in user experience screendrops, to that of \systemname, in common app workloads.