From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Jan Kara <jack@suse.cz>, Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Vinayak Menon <vinmenon@codeaurora.org>,
Hugh Dickins <hughd@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
kernel-team@android.com
Subject: [PATCH v4 3/8] arm64: mm: Implement arch_wants_old_prefaulted_pte()
Date: Wed, 20 Jan 2021 17:36:07 +0000 [thread overview]
Message-ID: <20210120173612.20913-4-will@kernel.org> (raw)
In-Reply-To: <20210120173612.20913-1-will@kernel.org>
On CPUs with hardware AF/DBM, initialising prefaulted PTEs as 'old'
improves vmscan behaviour and does not appear to introduce any overhead
elsewhere.
Implement arch_wants_old_prefaulted_pte() to return 'true' if we detect
hardware access flag support at runtime. This can be extended in future
based on MIDR matching if necessary.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/pgtable.h | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 501562793ce2..e17b96d0e4b5 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -980,7 +980,17 @@ static inline bool arch_faults_on_old_pte(void)
return !cpu_has_hw_af();
}
-#define arch_faults_on_old_pte arch_faults_on_old_pte
+#define arch_faults_on_old_pte arch_faults_on_old_pte
+
+/*
+ * Experimentally, it's cheap to set the access flag in hardware and we
+ * benefit from prefaulting mappings as 'old' to start with.
+ */
+static inline bool arch_wants_old_prefaulted_pte(void)
+{
+ return !arch_faults_on_old_pte();
+}
+#define arch_wants_old_prefaulted_pte arch_wants_old_prefaulted_pte
#endif /* !__ASSEMBLY__ */
--
2.30.0.284.gd98b1dd5eaa7-goog
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Nick Desaulniers <ndesaulniers@google.com>,
kernel-team@android.com, Jan Kara <jack@suse.cz>,
Minchan Kim <minchan@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, Vinayak Menon <vinmenon@codeaurora.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 3/8] arm64: mm: Implement arch_wants_old_prefaulted_pte()
Date: Wed, 20 Jan 2021 17:36:07 +0000 [thread overview]
Message-ID: <20210120173612.20913-4-will@kernel.org> (raw)
In-Reply-To: <20210120173612.20913-1-will@kernel.org>
On CPUs with hardware AF/DBM, initialising prefaulted PTEs as 'old'
improves vmscan behaviour and does not appear to introduce any overhead
elsewhere.
Implement arch_wants_old_prefaulted_pte() to return 'true' if we detect
hardware access flag support at runtime. This can be extended in future
based on MIDR matching if necessary.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/pgtable.h | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 501562793ce2..e17b96d0e4b5 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -980,7 +980,17 @@ static inline bool arch_faults_on_old_pte(void)
return !cpu_has_hw_af();
}
-#define arch_faults_on_old_pte arch_faults_on_old_pte
+#define arch_faults_on_old_pte arch_faults_on_old_pte
+
+/*
+ * Experimentally, it's cheap to set the access flag in hardware and we
+ * benefit from prefaulting mappings as 'old' to start with.
+ */
+static inline bool arch_wants_old_prefaulted_pte(void)
+{
+ return !arch_faults_on_old_pte();
+}
+#define arch_wants_old_prefaulted_pte arch_wants_old_prefaulted_pte
#endif /* !__ASSEMBLY__ */
--
2.30.0.284.gd98b1dd5eaa7-goog
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next prev parent reply other threads:[~2021-01-20 19:00 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 17:36 [PATCH v4 0/8] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 1/8] mm: Cleanup faultaround and finish_fault() codepaths Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 2/8] mm: Allow architectures to request 'old' entries when prefaulting Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 17:36 ` Will Deacon [this message]
2021-01-20 17:36 ` [PATCH v4 3/8] arm64: mm: Implement arch_wants_old_prefaulted_pte() Will Deacon
2021-01-20 17:36 ` [PATCH v4 4/8] mm: Move immutable fields of 'struct vm_fault' into anonymous struct Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 18:13 ` Nick Desaulniers
2021-01-20 18:13 ` Nick Desaulniers
2021-01-20 18:13 ` Nick Desaulniers
2021-01-21 12:48 ` Will Deacon
2021-01-21 12:48 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 5/8] mm: Pass 'address' to map to do_set_pte() and drop FAULT_FLAG_PREFAULT Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 6/8] mm: Avoid modifying vmf.address in __collapse_huge_page_swapin() Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 7/8] mm: Use static initialisers for immutable fields of 'struct vm_fault' Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 18:21 ` Nick Desaulniers
2021-01-20 18:21 ` Nick Desaulniers
2021-01-20 18:21 ` Nick Desaulniers
2021-01-21 12:50 ` Will Deacon
2021-01-21 12:50 ` Will Deacon
2021-01-20 17:36 ` [PATCH v4 8/8] mm: Mark anonymous struct field of 'struct vm_fault' as 'const' Will Deacon
2021-01-20 17:36 ` Will Deacon
2021-01-20 18:27 ` Nick Desaulniers
2021-01-20 18:27 ` Nick Desaulniers
2021-01-20 18:27 ` Nick Desaulniers
2021-01-20 19:02 ` Linus Torvalds
2021-01-20 19:02 ` Linus Torvalds
2021-01-20 19:02 ` Linus Torvalds
2021-01-21 13:11 ` Will Deacon
2021-01-21 13:11 ` Will Deacon
2021-01-21 19:24 ` Nick Desaulniers
2021-01-21 19:24 ` Nick Desaulniers
2021-01-21 19:24 ` Nick Desaulniers
2021-01-21 21:28 ` Will Deacon
2021-01-21 21:28 ` Will Deacon
2021-01-22 19:10 ` Nick Desaulniers
2021-01-22 19:10 ` Nick Desaulniers
2021-01-22 19:10 ` Nick Desaulniers
2021-01-22 19:27 ` Will Deacon
2021-01-22 19:27 ` Will Deacon
2021-01-22 17:47 ` Linus Torvalds
2021-01-22 17:47 ` Linus Torvalds
2021-01-22 17:47 ` Linus Torvalds
2021-01-26 23:08 ` [PATCH v4 0/8] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag Will Deacon
2021-01-26 23:08 ` Will Deacon
2021-01-26 23:28 ` Hugh Dickins
2021-01-26 23:28 ` Hugh Dickins
2021-01-26 23:28 ` Hugh Dickins
2021-01-27 17:16 ` Will Deacon
2021-01-27 17:16 ` Will Deacon
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