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| author | Peter Zijlstra <peterz@infradead.org> | 2025-09-17 13:03:20 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-09-25 10:51:50 +0300 |
| commit | a3a70caf7906708bf9bbc80018752a6b36543808 (patch) | |
| tree | 59039c38fa935f8a4c5fc9454ffa0d134cbb97cf /include/linux | |
| parent | 4ae8d9aa9f9dc7137ea5e564d79c5aa5af1bc45c (diff) | |
| download | linux-a3a70caf7906708bf9bbc80018752a6b36543808.tar.xz | |
sched/deadline: Fix dl_server behaviour
John reported undesirable behaviour with the dl_server since commit:
cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling").
When starving fair tasks on purpose (starting spinning FIFO tasks),
his fair workload, which often goes (briefly) idle, would delay fair
invocations for a second, running one invocation per second was both
unexpected and terribly slow.
The reason this happens is that when dl_se->server_pick_task() returns
NULL, indicating no runnable tasks, it would yield, pushing any later
jobs out a whole period (1 second).
Instead simply stop the server. This should restore behaviour in that
a later wakeup (which restarts the server) will be able to continue
running (subject to the CBS wakeup rules).
Notably, this does not re-introduce the behaviour cccb45d7c4295 set
out to solve, any start/stop cycle is naturally throttled by the timer
period (no active cancel).
Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling")
Reported-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: John Stultz <jstultz@google.com>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/sched.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index f89313b150e6..e4ce0a76831e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -706,7 +706,6 @@ struct sched_dl_entity { unsigned int dl_defer : 1; unsigned int dl_defer_armed : 1; unsigned int dl_defer_running : 1; - unsigned int dl_server_idle : 1; /* * Bandwidth enforcement timer. Each -deadline task has its |