From cccb45d7c4295bbfeba616582d0249f2d21e6df5 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 20 May 2025 11:19:30 +0200 Subject: sched/deadline: Less agressive dl_server handling Chris reported that commit 5f6bd380c7bd ("sched/rt: Remove default bandwidth control") caused a significant dip in his favourite benchmark of the day. Simply disabling dl_server cured things. His workload hammers the 0->1, 1->0 transitions, and the dl_server_{start,stop}() overhead kills it -- fairly obviously a bad idea in hind sight and all that. Change things around to only disable the dl_server when there has not been a fair task around for a whole period. Since the default period is 1 second, this ensures the benchmark never trips this, overhead gone. Fixes: 557a6bfc662c ("sched/fair: Add trivial fair server") Reported-by: Chris Mason Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Juri Lelli Acked-by: Juri Lelli Link: https://lkml.kernel.org/r/20250702121158.465086194@infradead.org --- include/linux/sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index eec6b225e9d1..4802fcf738cd 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -698,6 +698,7 @@ 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