linux-kernel - Re: [PATCH v4 5/5] x86: mremap speedup

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Date:   Wed, 14 Oct 2020 17:53:18 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Kalesh Singh <kaleshsingh@...gle.com>
Cc:     surenb@...gle.com, minchan@...gle.com, joelaf@...gle.com,
        lokeshgidra@...gle.com, kernel-team@...roid.com,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        Shuah Khan <shuah@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Hassan Naveed <hnaveed@...ecomp.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mark Rutland <mark.rutland@....com>,
        Gavin Shan <gshan@...hat.com>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        Jia He <justin.he@....com>, John Hubbard <jhubbard@...dia.com>,
        Ram Pai <linuxram@...ibm.com>,
        Sandipan Das <sandipan@...ux.ibm.com>, Zi Yan <ziy@...dia.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Dave Hansen <dave.hansen@...el.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: Re: [PATCH v4 5/5] x86: mremap speedup - Enable HAVE_MOVE_PUD


* Kalesh Singh <kaleshsingh@...gle.com> wrote:

> 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>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: H. Peter Anvin <hpa@...or.com>

Nice!

Assuming it's all correct code:

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo