on the ineffectiveness of 1/m-based interference bounds in...
TRANSCRIPT
On the Ineffectiveness of 1/m-based Interference Bounds in the
Analysis of Global EDF and FIFO Scheduling
Alessandro Biondi and Youcheng Sun
Scuola Superiore Sant’Anna, Pisa, Italy
University of Oxford, Oxford, UK
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Journal paper published in Real-Time Systems, July 2018, Volume 54, Issue 3, pp 515–536
2A. Biondi
Response-time analysis for sporadic tasks under global scheduling
• Most popular proposal due to Bertogna and Cirenei (RTSS’07)
• Extended to refine carry-in/carry-out interference
• The same analysis principle has been widely adopted as a building
block to analyze
RTA for Global Scheduling
locking protocols hierarchical scheduling
Vestal’s mixed-criticality schedulers
processor affinities
parallel tasks cache-related delays
priority assignments heterogeneous multiprocessors etc…
3A. Biondi
Response-time analysis for sporadic tasks under global scheduling
• Most popular proposal due to Bertogna and Cirenei (RTSS’07)
• Extended to refine carry-in/carry-out interference
• The same analysis principle has been widely adopted as a building
block to analyze
RTA for Global Scheduling
𝑅𝑖UB = 𝐶𝑖 +
𝟏
𝒎
othertasks 𝜏𝑗
<bound on interfering workload of 𝜏𝑗>
number of processors
Working principle: exploit work-conserving property to bound interference
locking protocols hierarchical scheduling
Vestal’s mixed-criticality schedulers
processor affinities
parallel tasks cache-related delays
priority assignments heterogeneous multiprocessors etc…
4A. Biondi
…it’s enough to sort the tasks by decreasing relative deadlines, and thenassign them to processors with any heuristic (e.g., first-fit)
Main results
If a set of sporadic real-time tasks is schedulable under
global EDF according to the Bertogna and Cirenei’s
analysis, then it is also schedulable under partitioned EDF
1
5A. Biondi
…it’s enough to sort the tasks by decreasing relative deadlines, and thenassign them to processors with any heuristic (e.g., first-fit)
Main results
If a set of sporadic real-time tasks is schedulable under
global EDF according to the Bertogna and Cirenei’s
analysis, then it is also schedulable under partitioned EDF
The same holds for global FIFO scheduling when analyzed
with a 1/m-based interference bound
1
2
E.g., relevant for multi-unit FIFO-based locking protocols
6A. Biondi
…it’s enough to sort the tasks by decreasing relative deadlines, and thenassign them to processors with any heuristic (e.g., first-fit)
Main results
If a set of sporadic real-time tasks is schedulable under
global EDF according to the Bertogna and Cirenei’s
analysis, then it is also schedulable under partitioned EDF
The same holds for global FIFO scheduling when analyzed
with a 1/m-based interference bound
Y. Sun and M. Di Natale, “Assessing the pessimism of current multicore global
fixed-priority schedulability analysis”, In Proceedings of the 33rd Annual ACM
Symposium on Applied Computing (SAC), April 9-13, 2018, Pau, France
…and also for global fixed-priority scheduling
1
2
E.g., relevant for multi-unit FIFO-based locking protocols
7A. Biondi
Take-away messages
G-EDF
P-EDF, first-fit, decreasing utilizations
utilization
sch
edu
lab
ility
rati
o• Besides the analytical
dominance, experimental
results showed that P-EDF
outperforms G-EDF withtoday’s analysis (30 heuristics
have been tested)
• The same emerged for FIFO
scheduling
(latest RTA RTSS’15)
8A. Biondi
Take-away messages
G-EDF
P-EDF, first-fit, decreasing utilizations
utilization
sch
edu
lab
ility
rati
o• Besides the analytical
dominance, experimental
results showed that P-EDF
outperforms G-EDF withtoday’s analysis (30 heuristics
have been tested)
• The same emerged for FIFO
scheduling
1/m-based analysis techniques for global scheduling are ineffective
with respect to much simpler and predictable partitioned schedulers
• Main source of pessimism is not related to carry-in and carry-out!
• What about other task models? What’s the impact on previous work?
(latest RTA RTSS’15)
9A. Biondi
Take-away messages
G-EDF
P-EDF, first-fit, decreasing utilizations
utilization
sch
edu
lab
ility
rati
o• Besides the analytical
dominance, experimental
results showed that P-EDF
outperforms G-EDF withtoday’s analysis (30 heuristics
have been tested)
• The same emerged for FIFO
scheduling
1/m-based analysis techniques for global scheduling are ineffective
with respect to much simpler and predictable partitioned schedulers
• Main source of pessimism is not related to carry-in and carry-out!
• What about other task models? What’s the impact on previous work?
Future analyses for global scheduling should always compare against
partitioned approaches
(latest RTA RTSS’15)
10A. Biondi
Take-away messages
G-EDF
P-EDF, first-fit, decreasing utilizations
utilization
sch
edu
lab
ility
rati
o• Besides the analytical
dominance, experimental
results showed that P-EDF
outperforms G-EDF withtoday’s analysis (30 heuristics
have been tested)
• The same emerged for FIFO
scheduling
1/m-based analysis techniques for global scheduling are ineffective
with respect to much simpler and predictable partitioned schedulers
• Main source of pessimism is not related to carry-in and carry-out!
• What about other task models? What’s the impact on previous work?
Future analyses for global scheduling should always compare against
partitioned approaches
Is global scheduling really the way to go? Anyway, we need new
analysis techniques…
(latest RTA RTSS’15)
Thank you!Alessandro Biondi
𝟏
𝒎
Do you want to know more about this work?
Come visiting me during the poster session!