linux-kernel - Re: [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick

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Date:   Fri, 13 Jul 2018 09:37:52 -0500
From:   Haris Okanovic <haris.okanovic@...com>
To:     Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        harisokn@...il.com, bigeasy@...utronix.de, tglx@...utronix.de,
        julia.cartwright@...com, gratian.crisan@...com, daniel@...stot.me,
        efault@....de
Subject: Re: [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick

Sounds good. I'll keep an eye out for your patch set and try it on my 
boards as well. CC me if you can.

-- Haris


On 07/13/2018 07:01 AM, Anna-Maria Gleixner wrote:
> 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
>