From: viresh kumar <viresh.kumar@linaro.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linaro-kernel@lists.linaro.org, patches@linaro.org,
bigeasy@linutronix.de, rostedt@goodmis.org, tj@kernel.org,
mingo@redhat.com, peterz@infradead.org,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
john.stultz@linaro.org, paulmck@linux.vnet.ibm.com
Subject: Re: [RFC] Timer: Migrate running timers
Date: Wed, 20 Nov 2013 19:57:29 +0530 [thread overview]
Message-ID: <528CC6D1.9010209@linaro.org> (raw)
In-Reply-To: <alpine.DEB.2.02.1311201148272.30673@ionos.tec.linutronix.de>
On Wednesday 20 November 2013 05:12 PM, Thomas Gleixner wrote:
> Viresh,
>
> On Wed, 20 Nov 2013, Viresh Kumar wrote:
>
>> Migration of timers from idle cores to non-idle ones for power saving is very
>> well working and really saves a lot of power for us. What's currently not
>> working is the migration of running timers Or timers which re-arms themselves.
>>
>> There are complications with migrating timers which schedules themselves again
>> from their handler. del_timer_sync() can't detect that the timer's handler
>> yet has not finished.
>
> Because you try to violate the semantics of the existing code. There
> is a reason why we enforce that running timers must be requeued on the
> base they are running on.
>
> Now you try to duct tape it into submission. That's not going to fly.
>
> The timer wheel code is not designed to allow that and it has lots of
> other short comings and historic burdens. I'm not going to accept more
> duct tape and fragile hackery into that code.
>
> I'm already working on a complete replacement infrastructure, which
> avoids all the short comings of the current timer implementation
> including this one.
>
> It's going to be a massive effort to convert everything over to the
> new infrastructure so we can kill the timer wheel, but that's less
> scary and less risky than trying to add more fragility to the existing
> code.
Thanks for the feedback. I Atleast know now that this patch doesn't have a future :)
prev parent reply other threads:[~2013-11-20 14:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 9:49 [RFC] Timer: Migrate running timers Viresh Kumar
2013-11-20 11:42 ` Thomas Gleixner
2013-11-20 14:27 ` viresh kumar [this message]
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