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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 2C398C433DF for ; Wed, 22 Jul 2020 18:05:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0342220787 for ; Wed, 22 Jul 2020 18:05:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="D6XVPjQC"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ZhTW850k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731727AbgGVSFZ (ORCPT ); Wed, 22 Jul 2020 14:05:25 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:51030 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbgGVSFY (ORCPT ); Wed, 22 Jul 2020 14:05:24 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1595441122; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HatAk6RLCg4BmgwgUUTlkbbDJ6PjhNZBQ9Tw9yFbT4I=; b=D6XVPjQCLKSWZPpdI6cMRuDA9c/iFta9Hfe/N1dPr6/12SHs+OIA610WTO40fMTDT8z6ge /RSxszDgWdBIe799CF4MT8UstcEUOjilZhXdTVMDCtHgBF49wKhzs+SX1twfEd1A+j0yUL 5iNnObdWMRql4ZklLvAd0b4nsx+W9xAFA/K9ZEDoRbhRTH9MwAdKrglBp+0fj1daIz4DrX mI26ifz6kZLk8C17WN0sSlmJNPHNhRgk2VX74Qmu95rjX4q+6pY4QV0Z1WXkJdIWdzqnoY 5fU87CNL8G/bikUObRBX5loS26/YRmfX5giqK5yLUdGDOMUW7aGjBmprriSjEg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1595441122; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HatAk6RLCg4BmgwgUUTlkbbDJ6PjhNZBQ9Tw9yFbT4I=; b=ZhTW850ki2WWzZ/FyUzSmrmqxZoHdvwjEDV12BXjtl4VwAvQTYr1aerN3GKu9kzCRfeuXu UhUMe1c0p5Oo4zAg== To: qianjun.kernel@gmail.com, peterz@infradead.org, will@kernel.org, luto@kernel.org, linux-kernel@vger.kernel.org, urezki@gmail.com Cc: laoar.shao@gmail.com, jun qian Subject: Re: [RFC PATCH v2] Softirq:avoid large sched delay from the pending softirqs In-Reply-To: <1595250506-9769-1-git-send-email-qianjun.kernel@gmail.com> References: <1595250506-9769-1-git-send-email-qianjun.kernel@gmail.com> Date: Wed, 22 Jul 2020 20:05:22 +0200 Message-ID: <87eep32zod.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org qianjun.kernel@gmail.com writes: > + > + end = ktime_get(); > + delta = ktime_to_us(end - start); What's the point of this conversion? That's a division for no value because you can simply define the maximum time in nanoseconds with the same effect, i.e. ktime_t end = ktime_get() + MAX_SOFTIRQ_TIME_NS; if (need_resched() && ktime_get() > end) break; So you can spare all that start, delta and conversion dance and keep the code simple. Also notice that need_resched() wants to be evaluated first because there is no point to do the more expensive time read if need_resched() is false. Thanks, tglx