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Date:   Fri, 13 Jul 2018 14:01:45 +0200 (CEST)
From:   Anna-Maria Gleixner <anna-maria@linutronix.de>
To:     Haris Okanovic <haris.okanovic@ni.com>
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>
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References: <7d21ff63-3dce-b8ea-a0f1-81d53617747d@ni.com> <20180628164036.27378-1-haris.okanovic@ni.com>
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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