github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-22 22:22:08 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

mm/vmalloc: use __this_cpu_try_cmpxchg() in preload_this_cpu_lock()

Browse Source 
Use __this_cpu_try_cmpxchg() instead of __this_cpu_cmpxchg (*ptr, old,
new) == old in preload_this_cpu_lock().  x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg.

The generated code improves from:

    4bb6:	48 85 f6             	test   %rsi,%rsi
    4bb9:	0f 84 10 fa ff ff    	je     45cf <...>
    4bbf:	4c 89 e8             	mov    %r13,%rax
    4bc2:	65 48 0f b1 35 00 00 	cmpxchg %rsi,%gs:0x0(%rip)
    4bc9:	00 00
    4bcb:	48 85 c0             	test   %rax,%rax
    4bce:	0f 84 fb f9 ff ff    	je     45cf <...>

to:

    4bb6:	48 85 f6             	test   %rsi,%rsi
    4bb9:	0f 84 10 fa ff ff    	je     45cf <...>
    4bbf:	4c 89 e8             	mov    %r13,%rax
    4bc2:	65 48 0f b1 35 00 00 	cmpxchg %rsi,%gs:0x0(%rip)
    4bc9:	00 00
    4bcb:	0f 84 fe f9 ff ff    	je     45cf <...>

No functional change intended.

Link: https://lkml.kernel.org/r/20240528144345.5980-2-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Uros Bizjak 2024-05-28 16:43:14 +02:00 committed by Andrew Morton
parent 21664442be
commit f56810c94c
1 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
mm/vmalloc.c
View File

@ -1816,7 +1816,7 @@ static void free_vmap_area(struct vmap_area *va)
static inline void
preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
{
struct vmap_area *va = NULL;
struct vmap_area *va = NULL, *tmp;
/*
* Preload this CPU with one extra vmap_area object. It is used
@ -1832,7 +1832,8 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
spin_lock(lock);
if (va && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, va))
tmp = NULL;
if (va && !__this_cpu_try_cmpxchg(ne_fit_preload_node, &tmp, va))
kmem_cache_free(vmap_area_cachep, va);
}