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From: Jean Tourrilhes <jt@bougret.hpl.hp.com>
To: Linux kernel mailing list <linux-kernel@vger.kernel.org>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: [QUESTION] Micro-Second timers in kernel ?
Date: Fri, 15 Mar 2002 16:48:45 -0800	[thread overview]
Message-ID: <20020315164845.A15889@bougret.hpl.hp.com> (raw)

	Hi,

	I'm wondering what is the lowest resolution of timers that can
be get in Linux across all platforms. The goal : I need to do
microsecond resolution delay in the hard_xmit function of the IrDA-USB
driver, and don't want to just grab the CPU.

	The function sys_nanosleep() seems to indicate that under 2ms,
we should not even bother using a timer. Well, on a modern CPU, 2ms is
a very long time (on the other hand, it seems OK for PDAs).
	The definition of "tick" in timer.c indicate that the timer_bh
is called at a maximum of HZ time per second (which is consistent with
the definition of jiffies). On i386, this would be one tick every
10ms.
	Well... I'm stuck. 10ms is a very long time at 4Mb/s. So, I
guess I'll continue to busy wait before sending each packet. Ugh !

	Regards,

	Jean

             reply	other threads:[~2002-03-16  0:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-03-16  0:48 Jean Tourrilhes [this message]
2002-03-16  2:42 ` george anzinger
2002-03-20 20:44   ` Kasper Dupont
2002-03-29  9:24     ` george anzinger

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