lkml.org 
[lkml]   [2015]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off
On Thu, 15 Jan 2015 21:27:14 -0600 (CST)
Christoph Lameter <cl@linux.com> wrote:

>
> The %gs register is not used since the address of the per cpu area is
> available as one of the first fields in the per cpu areas.

Have you disassembled your code?

Looking at put_cpu_partial() from 3.19-rc3 where it does:

oldpage = this_cpu_read(s->cpu_slab->partial);

I get:

mov %gs:0x18(%rax),%rdx

Looks to me that %gs is used.


I haven't done benchmarks in a while, so perhaps accessing the %gs
segment isn't as expensive as I saw it before. I'll have to profile
function tracing on my i7 and see where things are slow again.


-- Steve


\
 
 \ /
  Last update: 2015-01-16 05:01    [W:0.143 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site