From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Date: Tue, 23 Sep 2003 10:51:18 +0000 Subject: Re: NS83820 2.6.0-test5 driver seems unstable on IA64 Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Tue, 23 Sep 2003 20:40:05 +1000 Peter Chubb 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.