From: Nicholas Piggin <npiggin@gmail.com>
To: linux-mm@kvack.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH 3/3] mm: skip page_cpupid_reset_last atomic update if the value is already reset
Date: Sun, 20 Dec 2020 15:03:40 +1000 [thread overview]
Message-ID: <20201220050340.849754-3-npiggin@gmail.com> (raw)
In-Reply-To: <20201220050340.849754-1-npiggin@gmail.com>
Improves performance of a PROT_READ -> PROT_READ|PROT_WRITE -> store
microbenchmark (which goes via the wp_page_reuse fault path) by about
10% on a POWER9.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
include/linux/mm.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6ece500464e0..c0a9e8de0738 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1382,6 +1382,9 @@ static inline void __page_cpupid_reset_last(struct page *page)
static inline void page_cpupid_reset_last(struct page *page)
{
+ if (page_cpupid_last(page) == (-1 & LAST_CPUPID_MASK))
+ return;
+
page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
}
--
2.23.0
next prev parent reply other threads:[~2020-12-20 5:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-20 5:03 [PATCH 1/3] mm: prefix page_cpupid_reset_last as non-atomic Nicholas Piggin
2020-12-20 5:03 ` [PATCH 2/3] mm: add page_cpupid_reset_last atomic variant Nicholas Piggin
2020-12-20 5:03 ` Nicholas Piggin [this message]
2020-12-21 1:53 ` [PATCH 1/3] mm: prefix page_cpupid_reset_last as non-atomic huang ying
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