linux-kernel - Re: [patch 4 15/22] timer: Remove slack leftovers

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Message-ID: <CAHmME9pYtiUPT4JKg3qxvY=qpRM=oNL8ezXeB3NHFQ2dpZikZA@mail.gmail.com>
Date:	Fri, 22 Jul 2016 17:18:04 +0200
From:	"Jason A. Donenfeld" <Jason@...c4.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Chris Mason <clm@...com>,
	Arjan van de Ven <arjan@...radead.org>, rt@...utronix.de,
	Rik van Riel <riel@...hat.com>,
	George Spelvin <linux@...encehorizons.net>,
	Len Brown <lenb@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [patch 4 15/22] timer: Remove slack leftovers

Hi Thomas,

On Fri, Jul 22, 2016 at 3:04 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Well, this really depends on the TIMEOUT value you have. The code now does
> implicit batching for larger timeouts by queueing the timers into wheels with
> coarse grained granularity. As long as your new TIMEOUT value ends up in the
> same bucket then that's equivalent to the slack thing.
>
> Can you give me a ballpark of your TIMEOUT value?

Generally either 5 seconds, 10 seconds, or 25 seconds.

Are these okay? Is the 25 case substantially different from the 5 case?


> When you take the slow (queueing) path, it's still expensive, not as bad as
> the previous one, but not really cheap either.

Hmm, okay.