From: Mike Rapoport <rppt@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Christopher Lameter <cl@linux.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Elena Reshetova <elena.reshetova@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
James Bottomley <jejb@linux.ibm.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Mark Rutland <mark.rutland@arm.com>,
Michal Hocko <mhocko@suse.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Mike Rapoport <rppt@kernel.org>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Peter Zijlstra <peterz@infradead.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Roman Gushchin <guro@fb.com>, Shakeel B utt <shakeelb@google.com>,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
Yury Norov <yury.norov@gmail.com>,
linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org,
x86@kernel.org, kernel test robot <oliver.sang@intel.com>
Subject: [PATCH v3 2/2] secretmem: optimize page_is_secretmem()
Date: Tue, 20 Apr 2021 18:00:49 +0300 [thread overview]
Message-ID: <20210420150049.14031-3-rppt@kernel.org> (raw)
In-Reply-To: <20210420150049.14031-1-rppt@kernel.org>
From: Mike Rapoport <rppt@linux.ibm.com>
Kernel test robot reported -4.2% regression of will-it-scale.per_thread_ops
due to commit "mm: introduce memfd_secret system call to create "secret"
memory areas".
The perf profile of the test indicated that the regression is caused by
page_is_secretmem() called from gup_pte_range() (inlined by gup_pgd_range):
27.76 +2.5 30.23 perf-profile.children.cycles-pp.gup_pgd_range
0.00 +3.2 3.19 ± 2% perf-profile.children.cycles-pp.page_mapping
0.00 +3.7 3.66 ± 2% perf-profile.children.cycles-pp.page_is_secretmem
Further analysis showed that the slow down happens because neither
page_is_secretmem() nor page_mapping() are not inline and moreover,
multiple page flags checks in page_mapping() involve calling
compound_head() several times for the same page.
Make page_is_secretmem() inline and replace page_mapping() with page flag
checks that do not imply page-to-head conversion.
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
include/linux/secretmem.h | 26 +++++++++++++++++++++++++-
mm/secretmem.c | 12 +-----------
2 files changed, 26 insertions(+), 12 deletions(-)
diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
index 907a6734059c..b842b38cbeb1 100644
--- a/include/linux/secretmem.h
+++ b/include/linux/secretmem.h
@@ -4,8 +4,32 @@
#ifdef CONFIG_SECRETMEM
+extern const struct address_space_operations secretmem_aops;
+
+static inline bool page_is_secretmem(struct page *page)
+{
+ struct address_space *mapping;
+
+ /*
+ * Using page_mapping() is quite slow because of the actual call
+ * instruction and repeated compound_head(page) inside the
+ * page_mapping() function.
+ * We know that secretmem pages are not compound and LRU so we can
+ * save a couple of cycles here.
+ */
+ if (PageCompound(page) || !PageLRU(page))
+ return false;
+
+ mapping = (struct address_space *)
+ ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
+
+ if (mapping != page->mapping)
+ return false;
+
+ return page->mapping->a_ops == &secretmem_aops;
+}
+
bool vma_is_secretmem(struct vm_area_struct *vma);
-bool page_is_secretmem(struct page *page);
bool secretmem_active(void);
#else
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 3b1ba3991964..0bcd15e1b549 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -151,22 +151,12 @@ static void secretmem_freepage(struct page *page)
clear_highpage(page);
}
-static const struct address_space_operations secretmem_aops = {
+const struct address_space_operations secretmem_aops = {
.freepage = secretmem_freepage,
.migratepage = secretmem_migratepage,
.isolate_page = secretmem_isolate_page,
};
-bool page_is_secretmem(struct page *page)
-{
- struct address_space *mapping = page_mapping(page);
-
- if (!mapping)
- return false;
-
- return mapping->a_ops == &secretmem_aops;
-}
-
static struct vfsmount *secretmem_mnt;
static struct file *secretmem_file_create(unsigned long flags)
--
2.28.0
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next prev parent reply other threads:[~2021-04-20 15:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 15:00 [PATCH v3 0/2] secretmem: optimize page_is_secretmem() Mike Rapoport
2021-04-20 15:00 ` [PATCH v3 1/2] secretmem/gup: don't check if page is secretmem without reference Mike Rapoport
2021-04-20 15:17 ` David Hildenbrand
2021-04-20 15:00 ` Mike Rapoport [this message]
2021-05-07 15:01 ` [PATCH v3 2/2] secretmem: optimize page_is_secretmem() Matthew Wilcox
2021-05-08 17:51 ` rppt
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