i#6471 sched idle: Add idle time from blocking syscalls #6494
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Adds a longer waiting period on blocking syscalls using either provided output time or for instruction-based quanta a count of queue selections before a blocked input is actually selected. Since the scheduler does not have timer interrupts or regular points of control and relies on its user calling it, idle inputs are kept on the ready queue and are checked for becoming unblocked when the ready queue is queried. The wait duration is set based on the "wait time factor" which is the syscall latency divided by the context switch threshold multipled by a user-provided "block_time_scale" option which can be used to scale up or down the durations. The wait duration is erased on a direct switch to an input. Adds a new replay record type to represent idle time on replay. Augments the unit tests to include blocking high-latency syscalls to test the new feature in various sub-tests. Issue: #6471
abhinav92003
approved these changes
Dec 6, 2023
|
In further testing on large traces, I am actually having trouble getting enough idle time. I can get a number of idle periods but they never add up to a large % of the instruction count. (With large core count I can get plenty of idle time.). I can't get arbitrary idle times by raising the scale: the scheduler gets slow before I reach idle % targets. But, I think it is worth merging this as-is for now to get some base blocked-idle time in there for base testing, even if I figure out how to improve it later. |
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Adds a longer waiting period on blocking syscalls using either provided output time or for instruction-based quanta a count of queue selections before a blocked input is actually selected. Since the scheduler does not have timer interrupts or regular points of control and relies on its user calling it, idle inputs are kept on the ready queue and are checked for becoming unblocked when the ready queue is queried.
The wait duration is set based on the "wait time factor" which is the syscall latency divided by the context switch threshold multipled by a user-provided "block_time_scale" option which can be used to scale up or down the durations.
The wait duration is erased on a direct switch to an input.
Adds a new replay record type to represent idle time on replay.
Augments the unit tests to include blocking high-latency syscalls to test the new feature in various sub-tests.
Issue: #6471