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 28E93C433DF for ; Wed, 1 Jul 2020 01:10:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E242420771 for ; Wed, 1 Jul 2020 01:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593565847; bh=mr+rQe0l8XSIekeEQFmG7I8vyIFw4b1KDVO2WDIE5lc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0JIPYlCuvdmIN1hJiXSW5v2IwHynQ4qVowKSNbLiElKxc8p6pj2KiysO/AnS5MbiB hY3Ex96ZetryKVtqZSDwEM9mplVSX9PyRhvPDhaqjY7qpicaViUYxo1g6M642ws+gC gXt0aaLF4k5LSJcMSkauH5/7UyAstuonKg5nbsLE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726649AbgGABKp (ORCPT ); Tue, 30 Jun 2020 21:10:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:56972 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726555AbgGABKn (ORCPT ); Tue, 30 Jun 2020 21:10:43 -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 4516520780; Wed, 1 Jul 2020 01:10:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593565842; bh=mr+rQe0l8XSIekeEQFmG7I8vyIFw4b1KDVO2WDIE5lc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wJZDTK6GDUNZbV4QtJGgNeRrtwxFjmld8mukrjb6nZXFlYINfDhiIvYgoSwlFJCgh y12cc4o2EEvmteqk9Gvm6QRBh6fq7s67WzXfketN+hfnObaCPvtJmO+StBEH/+So88 E6jzhF6mJDuwDsgoE8EjPiDdXqZEAjj6h5MWBDSc= From: Frederic Weisbecker To: Thomas Gleixner Cc: LKML , Frederic Weisbecker , Anna-Maria Gleixner , Peter Zijlstra , Juri Lelli Subject: [RFC PATCH 04/10] timer: Optimize _next_timer_interrupt() level iteration Date: Wed, 1 Jul 2020 03:10:24 +0200 Message-Id: <20200701011030.14324-5-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 If a level has a timer that expires before we reach the next level, there is no need to iterate further. The next level is reached when the 3 lower bits of the current level are cleared. If the next event happens before/during that, the next levels won't give us an earlier expiration. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Anna-Maria Gleixner Cc: Juri Lelli --- kernel/time/timer.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index b4838d63a016..4aa74aafdd33 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1515,6 +1515,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) clk = base->clk; for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) { int pos = next_pending_bucket(base, offset, clk & LVL_MASK); + unsigned long lvl_clk = clk & LVL_CLK_MASK; if (pos >= 0) { unsigned long tmp = clk + (unsigned long) pos; @@ -1522,6 +1523,13 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) tmp <<= LVL_SHIFT(lvl); if (time_before(tmp, next)) next = tmp; + + /* + * If the next expiration happens before we reach + * the next level, no need to check further. + */ + if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK)) + break; } /* * Clock for the next level. If the current level clock lower @@ -1559,7 +1567,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) * So the simple check whether the lower bits of the current * level are 0 or not is sufficient for all cases. */ - adj = clk & LVL_CLK_MASK ? 1 : 0; + adj = lvl_clk ? 1 : 0; clk >>= LVL_CLK_SHIFT; clk += adj; } -- 2.26.2