linux-kernel - [PATCH v2 6/6] x86: mremap speedup

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Date:   Fri,  2 Oct 2020 16:20:51 +0000
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     surenb@...gle.com, minchan@...gle.com, joelaf@...gle.com,
        lokeshgidra@...gle.com, kaleshsingh@...gle.com,
        kernel-team@...roid.com, Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Hassan Naveed <hnaveed@...ecomp.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Mike Rapoport <rppt@...nel.org>, Gavin Shan <gshan@...hat.com>,
        Zhenyu Ye <yezhenyu2@...wei.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Jia He <justin.he@....com>, John Hubbard <jhubbard@...dia.com>,
        Zi Yan <ziy@...dia.com>, Dave Hansen <dave.hansen@...el.com>,
        Mina Almasry <almasrymina@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ram Pai <linuxram@...ibm.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Sandipan Das <sandipan@...ux.ibm.com>,
        Brian Geffon <bgeffon@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        SeongJae Park <sjpark@...zon.de>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH v2 6/6] x86: mremap speedup - Enable HAVE_MOVE_PUD

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@...gle.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7101ac64bb20..ff6e2755cab8 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
-- 
2.28.0.806.g8561365e88-goog