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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 38FA3ECDFB0 for ; Fri, 13 Jul 2018 12:01:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E7E60208E2 for ; Fri, 13 Jul 2018 12:01:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E7E60208E2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729785AbeGMMQQ (ORCPT ); Fri, 13 Jul 2018 08:16:16 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:47088 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727608AbeGMMQQ (ORCPT ); Fri, 13 Jul 2018 08:16:16 -0400 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] helo=[10.100.61.71]) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1fdwle-00036d-02; Fri, 13 Jul 2018 14:01:46 +0200 Date: Fri, 13 Jul 2018 14:01:45 +0200 (CEST) From: Anna-Maria Gleixner To: Haris Okanovic cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, harisokn@gmail.com, bigeasy@linutronix.de, tglx@linutronix.de, julia.cartwright@ni.com, gratian.crisan@ni.com, daniel@bristot.me, efault@gmx.de Subject: Re: [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick In-Reply-To: <20180628164036.27378-1-haris.okanovic@ni.com> Message-ID: References: <7d21ff63-3dce-b8ea-a0f1-81d53617747d@ni.com> <20180628164036.27378-1-haris.okanovic@ni.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Haris, On Thu, 28 Jun 2018, Haris Okanovic wrote: > Collect expired timers in interrupt context to avoid overhead of waking > ktimersoftd on every scheduler tick. > > This is implemented by storing lists of expired timers in the timer_base > struct, which is updated by the interrupt routing on each tick in > run_local_timers(). TIMER softirq (ktimersoftd) is then raised only when > one or more expired timers are collected. > > Performance impact on a 2core Intel Atom E3825 system: > * reduction in small latency spikes measured by cyclictest > * ~30% fewer context-switches measured by perf > * run_local_timers() execution time increases by 0.2 measured by TSC > I'm also working on timer improvements at the moment. When I fixed all my bugs in my implementation (there is a last horrible one), I'm very interested in integrating your patches into my testing to be able to give you a tested-by. Thanks, Anna-Maria