linux-kernel - Re: [patch V3 38/38] posix-cpu-timers: Utilize timerqueue for storage

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Message-ID: <20190827222340.GB25843@lenoir>
Date:   Wed, 28 Aug 2019 00:23:41 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <john.stultz@...aro.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Christoph Hellwig <hch@....de>
Subject: Re: [patch V3 38/38] posix-cpu-timers: Utilize timerqueue for storage

On Tue, Aug 27, 2019 at 09:31:02PM +0200, Thomas Gleixner wrote:
> Using a linear O(N) search for timer insertion affects execution time and
> D-cache footprint badly with a larger number of timers.
> 
> Switch the storage to a timerqueue which is already used for hrtimers and
> alarmtimers. It does not affect the size of struct k_itimer as it.alarm is
> still larger.
> 
> The extra list head for the expiry list will go away later once the expiry
> is moved into task work context.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V2: Adopt to the per clock base struct
> V3: Fixup memset() and clear cputtimer::head in cleanup_timerqueue()

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>