From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0485C433DF for ; Wed, 1 Jul 2020 01:11:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A92C420780 for ; Wed, 1 Jul 2020 01:11:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593565862; bh=N+mVRYojS/sgF3AShn1/nfVqZdHfXdbQ40Gc/VFNccg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LEJXaq9ex7WcdHTA/tSVPTH8o9JR3VftN0fZW2Ra0P1/AX0srXrBToG8BBz/zovM+ yI6aE+8Xzz0sN6L5PqnR6IAKRnqQfRa2uN+zKnkF+9gtM+T+I7JxlgZNs0ebp4+Qma MHFFkVqymw72z7iXU0KGOXBMv/KX4IghH5HDz3TE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726842AbgGABLB (ORCPT ); Tue, 30 Jun 2020 21:11:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:57104 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbgGABKt (ORCPT ); Tue, 30 Jun 2020 21:10:49 -0400 Received: from lenoir.home (lfbn-ncy-1-996-218.w90-101.abo.wanadoo.fr [90.101.73.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9030820780; Wed, 1 Jul 2020 01:10:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593565848; bh=N+mVRYojS/sgF3AShn1/nfVqZdHfXdbQ40Gc/VFNccg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aBaweMGX+MlYORgKOWNtedK0Onh/3xY654VISkwQWX2lCCTWiwjzzpjVROyvq7SYY UB7XCxdbABHhZUdXxNTFubDysvFWDTZe/VTvm7SqeplJcBHxLDXS4z44y+2wPMU3Tt 0tX4+HbIp4PfWNPBwj32o+UI5F8MQDKHca/wmzEw= From: Frederic Weisbecker To: Thomas Gleixner Cc: LKML , Frederic Weisbecker , Anna-Maria Gleixner , Peter Zijlstra , Juri Lelli Subject: [RFC PATCH 08/10] timer: Spare timer softirq until next expiry Date: Wed, 1 Jul 2020 03:10:28 +0200 Message-Id: <20200701011030.14324-9-frederic@kernel.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200701011030.14324-1-frederic@kernel.org> References: <20200701011030.14324-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that the core timer infrastructure doesn't depend anymore on periodic base->clk increments, even when the CPU is not in NO_HZ mode, we can delay the timer softirqs until we have actual timers to expire. Some spurious softirqs can still remain since base->next_expiry doesn't keep track of canceled timers but we are still way ahead of the unconditional periodic softirqs (~15 times less of them with 1000 Hz and ~5 times less with 100 Hz). Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Anna-Maria Gleixner Cc: Juri Lelli --- kernel/time/timer.c | 49 ++++++++------------------------------------- 1 file changed, 8 insertions(+), 41 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 6c021be0e76f..95f51b646447 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1449,10 +1449,10 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head) } } -static int __collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) +static int collect_expired_timers(struct timer_base *base, + struct hlist_head *heads) { - unsigned long clk = base->clk; + unsigned long clk = base->clk = base->next_expiry; struct hlist_head *vec; int i, levels = 0; unsigned int idx; @@ -1675,40 +1675,6 @@ void timer_clear_idle(void) */ base->is_idle = false; } - -static int collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) -{ - unsigned long now = READ_ONCE(jiffies); - - /* - * NOHZ optimization. After a long idle sleep we need to forward the - * base to current jiffies. Avoid a loop by searching the bitfield for - * the next expiring timer. - */ - if ((long)(now - base->clk) > 2) { - /* - * If the next timer is ahead of time forward to current - * jiffies, otherwise forward to the next expiry time: - */ - if (time_after(base->next_expiry, now)) { - /* - * The call site will increment base->clk and then - * terminate the expiry loop immediately. - */ - base->clk = now; - return 0; - } - base->clk = base->next_expiry; - } - return __collect_expired_timers(base, heads); -} -#else -static inline int collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) -{ - return __collect_expired_timers(base, heads); -} #endif /* @@ -1741,7 +1707,7 @@ static inline void __run_timers(struct timer_base *base) struct hlist_head heads[LVL_DEPTH]; int levels; - if (!time_after_eq(jiffies, base->clk)) + if (time_before(jiffies, base->next_expiry)) return; timer_base_lock_expiry(base); @@ -1754,7 +1720,8 @@ static inline void __run_timers(struct timer_base *base) */ base->must_forward_clk = false; - while (time_after_eq(jiffies, base->clk)) { + while (time_after_eq(jiffies, base->clk) && + time_after_eq(jiffies, base->next_expiry)) { levels = collect_expired_timers(base, heads); base->clk++; @@ -1789,12 +1756,12 @@ void run_local_timers(void) hrtimer_run_queues(); /* Raise the softirq only if required. */ - if (time_before(jiffies, base->clk)) { + if (time_before(jiffies, base->next_expiry)) { if (!IS_ENABLED(CONFIG_NO_HZ_COMMON)) return; /* CPU is awake, so check the deferrable base. */ base++; - if (time_before(jiffies, base->clk)) + if (time_before(jiffies, base->next_expiry)) return; } raise_softirq(TIMER_SOFTIRQ); -- 2.26.2