* [PATCH] mm/rmap: use atomic_try_cmpxchg in set_tlb_ubc_flush_pending
@ 2023-02-27 21:42 Uros Bizjak
0 siblings, 0 replies; only message in thread
From: Uros Bizjak @ 2023-02-27 21:42 UTC (permalink / raw)
To: linux-mm, linux-kernel; +Cc: Uros Bizjak, Andrew Morton
Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old in
set_tlb_ubc_flush_pending. 86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move instruction in
front of cmpxchg).
Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
mm/rmap.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 15ae24585fc4..f964c197fc3c 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -644,7 +644,7 @@ void try_to_unmap_flush_dirty(void)
static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
{
struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
- int batch, nbatch;
+ int batch;
arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
tlb_ubc->flush_required = true;
@@ -662,11 +662,8 @@ static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
* overflow. Reset `pending' and `flushed' to be 1 and 0 if
* `pending' becomes large.
*/
- nbatch = atomic_cmpxchg(&mm->tlb_flush_batched, batch, 1);
- if (nbatch != batch) {
- batch = nbatch;
+ if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1))
goto retry;
- }
} else {
atomic_inc(&mm->tlb_flush_batched);
}
--
2.39.2
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