From a3a70caf7906708bf9bbc80018752a6b36543808 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 17 Sep 2025 12:03:20 +0200 Subject: 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 Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Peter Zijlstra (Intel) Tested-by: John Stultz --- include/linux/sched.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux') 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 -- cgit v1.2.3