lkml.org 
[lkml]   [2006]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] percpu data: only iterate over possible CPUs
Andrew Morton a écrit :
> Andi Kleen <ak@muc.de> wrote:
>> On Thursday 09 February 2006 19:04, Andrew Morton wrote:
>>> Ashok Raj <ashok.raj@intel.com> wrote:
>>>> The problem was with ACPI just simply looking at the namespace doesnt
>>>> exactly give us an idea of how many processors are possible in this platform.
>>> We need to fix this asap - the performance penalty for HOTPLUG_CPU=y,
>>> NR_CPUS=lots will be appreciable.
>> What is this performance penalty exactly?
>
> All those for_each_cpu() loops will hit NR_CPUS cachelines instead of
> hweight(cpu_possible_map) cachelines.

You mean NR_CPUS bits, mostly all included in a single cacheline, and even in
a single long word :) for most cases (NR_CPUS <= 32 or 64)



-
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/

\
 
 \ /
  Last update: 2006-02-10 12:13    [W:0.240 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site