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Date: Tue, 23 Sep 2003 03:51:18 -0700
From: "David S. Miller" <davem@redhat.com>
To: Peter Chubb <peter@chubb.wattle.id.au>
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Subject: Re: NS83820 2.6.0-test5 driver seems unstable on IA64
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On Tue, 23 Sep 2003 20:40:05 +1000
Peter Chubb <peter@chubb.wattle.id.au> wrote:

> How expensive is it to take the trap and do a fix up, compared to
> making an aligned copy?  As it involves raising and handling a fault
> disassembling the instruction that caused the fault, etc., I'd be
> surprised if it's much less than 1000 cycles, even without the printk,
> although I haven't measured it yet, and can't find enough info in the
> architecture manuals to know what it is.

A cache miss can cause 100 or so cycles. :)

And unlike the fixup trap, the printk wakes up a process and
causes disk activity as syslogd writes to the kernel message
log file.