lkml.org 
[lkml]   [2021]   [Feb]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm/slub: embed __slab_alloc to its caller
From
Date
On 2/3/21 2:41 AM, Abel Wu wrote:
>> On Feb 2, 2021, at 6:11 PM, Christoph Lameter <cl@linux.com> wrote:
>>
>> On Tue, 2 Feb 2021, Abel Wu wrote:
>>
>>> Since slab_alloc_node() is the only caller of __slab_alloc(), embed
>>> __slab_alloc() to its caller to save function call overhead. This
>>> will also expand the caller's code block size a bit, but hackbench
>>> tests on both host and guest didn't show a difference w/ or w/o
>>> this patch.
>>
>> slab_alloc_node is an always_inline function. It is intentional that only
>> the fast path was inlined and not the slow path.
>
> Oh I got it. Thanks for your excellent explanation.

BTW, there's a script in the Linux source to nicely see the effect of such changes:

./scripts/bloat-o-meter slub.o.before mm/slub.o
add/remove: 0/1 grow/shrink: 9/0 up/down: 1660/-1130 (530)
Function old new delta
__slab_alloc 127 1130 +1003
__kmalloc_track_caller 877 965 +88
__kmalloc 878 966 +88
kmem_cache_alloc 778 862 +84
__kmalloc_node_track_caller 996 1080 +84
kmem_cache_alloc_node_trace 813 896 +83
kmem_cache_alloc_node 800 881 +81
kmem_cache_alloc_trace 786 862 +76
__kmalloc_node 998 1071 +73
___slab_alloc 1130 - -1130
Total: Before=57782, After=58312, chg +0.92%

And yeah, bloating all the entry points wouldn't be nice.
Thanks,
Vlastimil

\
 
 \ /
  Last update: 2021-02-05 14:11    [W:0.055 / U:3.660 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site