From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Luck Date: Sun, 22 Jan 2006 20:59:02 +0000 Subject: Re: [PATCH] disable per cpu intr in /proc/stat Message-Id: <12c511ca0601221259i25f26410l5c94871b7495283f@mail.gmail.com> List-Id: References: <20060122202204.GA26295@suse.de> <20060122123150.3a289ac3.akpm@osdl.org> In-Reply-To: <20060122123150.3a289ac3.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrew Morton Cc: Olaf Hering , linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org On 1/22/06, Andrew Morton wrote: > Olaf Hering wrote: > > Don't compute and display the per-irq sums on ia64 either, too much > > overhead for mostly useless figures. > > We'd need a big ack from the ia64 team for this, please. This was found early in December. I proposed: http://marc.theaimsgroup.com/?l=linux-kernel&m3398553428807&w=2 dropping it for all architectures, but got no response. The problem is the horribly cache unfriendly scan of all percpu structures ... not too much of a problem for low cpu count, but really bad when the count gets high (just configured high is enough to cause the problem in a CONFIG_HOTPLUG_CPU kernel ... even if the cpu isn't present we still scan). An alternative if someone really is using these values would be to compute the sums earlier in the function ... but that would require a memory allocation to save the per-irq sums. Unless someone comes up soon with the name of an existing application that depends on these per-irq sums, consider this Acked-by: Tony Luck -Tony