lkml.org 
[lkml]   [2012]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] x86: don't ever patch back to UP if we unplug cpus.
From
Date
On Mon, 2012-07-30 at 11:40 +0930, Rusty Russell wrote:
> We still patch SMP instructions to UP variants if we boot with a
> single CPU, but not at any other time. In particular, not if we
> unplug CPUs to return to a single cpu.
>
> Paul McKenney points out:
>
> mean offline overhead is 6251/48=130.2 milliseconds.
>
> If I remove the alternatives_smp_switch() from the offline
> path [...] the mean offline overhead is 550/42=13.1 milliseconds
>
> Basically, we're never going to get those 120ms back, and the code is
> pretty messy.
>
> We get rid of:
> 1) The "smp-alt-once" boot option. It's actually "smp-alt-boot", the
> documentation is wrong. It's now the default.
> 2) The skip_smp_alternatives flag used by suspend.
> 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end()
> which were only used to set this one flag.
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>



\
 
 \ /
  Last update: 2012-07-30 19:41    [W:0.113 / U:0.944 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site