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Date:   Wed, 14 Oct 2020 00:53:10 +0000
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Subject: [PATCH v4 5/5] x86: mremap speedup - Enable HAVE_MOVE_PUD
From:   Kalesh Singh <kaleshsingh@google.com>
Cc:     surenb@google.com, minchan@google.com, joelaf@google.com,
        lokeshgidra@google.com, kaleshsingh@google.com,
        kernel-team@android.com,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, x86@kernel.org,
        Shuah Khan <shuah@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Sami Tolvanen <samitolvanen@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Hassan Naveed <hnaveed@wavecomp.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Gavin Shan <gshan@redhat.com>, Mike Rapoport <rppt@kernel.org>,
        Steven Price <steven.price@arm.com>,
        Jia He <justin.he@arm.com>, John Hubbard <jhubbard@nvidia.com>,
        Ram Pai <linuxram@us.ibm.com>,
        Sandipan Das <sandipan@linux.ibm.com>, Zi Yan <ziy@nvidia.com>,
        Mina Almasry <almasrymina@google.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Brian Geffon <bgeffon@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        SeongJae Park <sjpark@amazon.de>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org
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HAVE_MOVE_PUD enables remapping pages at the PUD level if both the
source and destination addresses are PUD-aligned.

With HAVE_MOVE_PUD enabled it can be inferred that there is approximately
a 13x improvement in performance on x86. (See data below).

------- Test Results ---------

The following results were obtained using a 5.4 kernel, by remapping
a PUD-aligned, 1GB sized region to a PUD-aligned destination.
The results from 10 iterations of the test are given below:

Total mremap times for 1GB data on x86. All times are in nanoseconds.

Control        HAVE_MOVE_PUD

180394         15089
235728         14056
238931         25741
187330         13838
241742         14187
177925         14778
182758         14728
160872         14418
205813         15107
245722         13998

205721.5       15594    <-- Mean time in nanoseconds

A 1GB mremap completion time drops from ~205 microseconds
to ~15 microseconds on x86. (~13x speed up).

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
---
Changes in v4:
  - Add Kirill's Acked-by.

 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 835d93006bd6..e199760d54fc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -198,6 +198,7 @@ config X86
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_MOVE_PMD
+	select HAVE_MOVE_PUD
 	select HAVE_NMI
 	select HAVE_OPROFILE
 	select HAVE_OPTPROBES
-- 
2.28.0.1011.ga647a8990f-goog