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From:   Lorenzo Colitti <lorenzo@google.com>
Date:   Tue, 20 Apr 2021 17:15:03 +0900
Message-ID: <CAKD1Yr1o=zN5K9PaB3wag5xOS2oY6AzEsV6dmL7pnTysK_GOhA@mail.gmail.com>
Subject: Re: [PATCH] hrtimer: Update softirq_expires_next correctly after __hrtimer_get_next_event()
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        =?UTF-8?Q?Maciej_=C5=BBenczykowski?= <zenczykowski@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>,
        mikael.beckius@windriver.com,
        =?UTF-8?Q?Maciej_=C5=BBenczykowski?= <maze@google.com>
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On Fri, Apr 16, 2021 at 1:47 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> Enable tracing and enable the following tracepoints:
> [...]

Sorry for the delay. I had to learn a bit about how to use the tracing
infrastructure. I don't know if I can post here, but to my untrained
eye, one big difference between the old (fast) code and the new (slow)
code is that the new code calls tick_program_event() much more. It
looks like that makes most of the difference.

With the old code, hrtimer_start_range_ns almost never calls
tick_program_event at all, but the new code seems to call it twice on
every timer update.