* [PATCH v2] mm/mremap_pages: Save a few cycles in get_dev_pagemap()
@ 2022-09-02 16:39 Christophe JAILLET
0 siblings, 0 replies; only message in thread
From: Christophe JAILLET @ 2022-09-02 16:39 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, kernel-janitors, Christophe JAILLET, linux-mm
Use 'percpu_ref_tryget_live_rcu()' instead of 'percpu_ref_tryget_live()' to
save a few cycles when it is known that the rcu lock is already
taken/released.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Matthew Wilcox <willy@infradead.org> commented on v1 that it is just a slow
path... but it is also just an easy patch :)
If considered as useless, let me know and I'll drop it from my WIP list.
Changes in v2:
* (no code change)
* synch with latest -next
v1:
https://lore.kernel.org/all/b4a47154877853cc64be3a35dcfd594d40cc2bce.1635975283.git.christophe.jaillet@wanadoo.fr/
---
mm/memremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/memremap.c b/mm/memremap.c
index 58b20c3c300b..25029a474d30 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -454,7 +454,7 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
/* fall back to slow path lookup */
rcu_read_lock();
pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
- if (pgmap && !percpu_ref_tryget_live(&pgmap->ref))
+ if (pgmap && !percpu_ref_tryget_live_rcu(&pgmap->ref))
pgmap = NULL;
rcu_read_unlock();
--
2.34.1
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