From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anna-Maria Gleixner Subject: Re: [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick Date: Fri, 13 Jul 2018 14:01:45 +0200 (CEST) Message-ID: References: <7d21ff63-3dce-b8ea-a0f1-81d53617747d@ni.com> <20180628164036.27378-1-haris.okanovic@ni.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 To: Haris Okanovic Return-path: In-Reply-To: <20180628164036.27378-1-haris.okanovic@ni.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.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