| Message ID | 20240523080136.9863-2-ubizjak@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] percpu: Add __this_cpu_try_cmpxchg() | expand |
> 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. > Just a small note. Can you also add a tiny difference in assembly language where it is visible? I mean update a commit message. -- Uladzislau Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 6641be0ca80b..0120faee5471 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -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); }
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. No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Uladzislau Rezki <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> --- mm/vmalloc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)