From: Peter Zijlstra Date: Tue, 24 Feb 2026 16:36:06 +0000 (+0100) Subject: sched/hrtick: Mark hrtick timer LAZY_REARM X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0abec32a6836eca6b61ae81e4829f94abd4647c7;p=thirdparty%2Fkernel%2Flinux.git sched/hrtick: Mark hrtick timer LAZY_REARM The hrtick timer is frequently rearmed before expiry and most of the time the new expiry is past the armed one. As this happens on every context switch it becomes expensive with scheduling heavy work loads especially in virtual machines as the "hardware" reprogamming implies a VM exit. hrtimer now provide a lazy rearm mode flag which skips the reprogamming if: 1) The timer was the first expiring timer before the rearm 2) The new expiry time is farther out than the armed time This avoids a massive amount of reprogramming operations of the hrtick timer for the price of eventually taking the alredy armed interrupt for nothing. Mark the hrtick timer accordingly. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260224163429.475409346@kernel.org --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5bc446e1b3d66..2d1239a8b2306 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -998,7 +998,8 @@ static void hrtick_rq_init(struct rq *rq) { INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq); rq->hrtick_sched = HRTICK_SCHED_NONE; - hrtimer_setup(&rq->hrtick_timer, hrtick, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); + hrtimer_setup(&rq->hrtick_timer, hrtick, CLOCK_MONOTONIC, + HRTIMER_MODE_REL_HARD | HRTIMER_MODE_LAZY_REARM); } #else /* !CONFIG_SCHED_HRTICK: */ static inline void hrtick_clear(struct rq *rq) { }