lkml.org 
[lkml]   [2010]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 34/35] x86: use num_processors for possible cpus
On 02/18/2010 11:48 AM, Christoph Lameter wrote:
>>
>> Yes, and I have repeatedly requested that we allocate the memory on the
>> first up of a disabled CPU rather than eagerly, but in *most*
>> configurations the amount is relatively small.
>
> The size of the static per cpu segment is likely around 30k and you will
> likely add another 30k in dynamic allocations.
>
> As I have also repeatedly stated: Dynamic percpu data allocation when
> onlining / offlining processors will complicate locking (cannot rely on
> percpu be present anymore) and introduce numerous additional
> hotplug notifiers into subsystems.

I did state explicitly "on first up". Trying to free it would be
insane. There are a couple of subsystems which are percpu memory
pigs... so far it's not clear any of them actually matters in a
production kernel. 60K * 16 phantom processors is still ~ 1 MB, which
probably isn't enough to worry about but isn't great.

-hpa


\
 
 \ /
  Last update: 2010-02-18 20:57    [W:0.113 / U:0.572 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site