linux-kernel - [patch 0/2] Introduce round_jiffies() to save spurious wakeups

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Date:	Tue, 10 Oct 2006 18:02:45 +0200
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...l.org, mingo@...e.hu
Subject: [patch 0/2] Introduce round_jiffies() to save spurious wakeups

Hi,

the following 2 patches will introduce the round_jiffies() api and users
thereof. 

The general idea is that by rounding the jiffies for certain timers to
the next whole second will make those timers all happen at the same
time; and thus reduce the number of times the cpu has to wake up to
service timers (this assumes a tickless kernel)

Obviously only timers where the exact time of firing isn't so important
can do this; several of the recurring "always live" timers of the kernel
are of this kind, they want "about once a second" or "about once every 4
seconds" and such, and don't really care about the exact jiffy in which
they fire.

An alternative would have been to introduce mod_timer_rounded() or
somesuch APIs (but there's many variants that take jiffies); I feel that
an explicit caller based rounding actually is quite reasonable.

Greetings,
   Arjan van de Ven
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