Date: Mon, 26 May 2003 18:17:34 -0700 (PDT)
Message-Id: <20030526.181734.68129361.davem@redhat.com>
To: davej@codemonkey.org.uk
Cc: andrea@suse.de, akpm@digeo.com, davidsen@tmr.com, haveblue@us.ibm.com,
       habanero@us.ibm.com, mbligh@aracnet.com, linux-kernel@vger.kernel.org
Subject: Re: userspace irq balancer
From: "David S. Miller" <davem@redhat.com>
In-Reply-To: <20030527011620.GB7135@suse.de>
References: <20030526.174841.116378513.davem@redhat.com>
	<20030527010903.GF3767@dualathlon.random>
	<20030527011620.GB7135@suse.de>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 954
Lines: 24

   From: Dave Jones <davej@codemonkey.org.uk>
   Date: Tue, 27 May 2003 02:16:20 +0100

   On Tue, May 27, 2003 at 03:09:03AM +0200, Andrea Arcangeli wrote:
   
    > rdtsc could do it very well, irqs and softirqs can't be rescheduled so
    > you can tick measure how long you take in each cpu
   
   On CPUs that vary frequency, this will break, unless TSC scales
   with frequency. You cannot assume that this will be the case.

This is an important issue, for another reason.

The networking packet scheduler layer wants an accurate (but
cheap) high frequency time source too.

I keep forgetting to go back and deal with fixing up all of
those hairy macros in pkt_sched.h, I've added this to my TODO
list.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/