linux-kernel - Re: [PATCH 0/5] Speed up mremap on large regions

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Message-ID: <20200930223207.5xepuvu6wr6xw5bb@black.fi.intel.com>
Date:   Thu, 1 Oct 2020 01:32:07 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Kalesh Singh <kaleshsingh@...gle.com>
Cc:     surenb@...gle.com, minchan@...gle.com, joelaf@...gle.com,
        lokeshgidra@...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>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Frederic Weisbecker <frederic@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Hassan Naveed <hnaveed@...ecomp.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...nel.org>, Gavin Shan <gshan@...hat.com>,
        Zhenyu Ye <yezhenyu2@...wei.com>, Jia He <justin.he@....com>,
        John Hubbard <jhubbard@...dia.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Sandipan Das <sandipan@...ux.ibm.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Ram Pai <linuxram@...ibm.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Brian Geffon <bgeffon@...gle.com>,
        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 0/5] Speed up mremap on large regions

On Wed, Sep 30, 2020 at 10:21:17PM +0000, Kalesh Singh wrote:
> mremap time can be optimized by moving entries at the PMD/PUD level if
> the source and destination addresses are PMD/PUD-aligned and
> PMD/PUD-sized. Enable moving at the PMD and PUD levels on arm64 and
> x86. Other architectures where this type of move is supported and known to
> be safe can also opt-in to these optimizations by enabling HAVE_MOVE_PMD
> and HAVE_MOVE_PUD.
> 
> Observed Performance Improvements for remapping a PUD-aligned 1GB-sized
> region on x86 and arm64:
> 
>     - HAVE_MOVE_PMD is already enabled on x86 : N/A
>     - Enabling HAVE_MOVE_PUD on x86   : ~13x speed up
> 
>     - Enabling HAVE_MOVE_PMD on arm64 : ~ 8x speed up
>     - Enabling HAVE_MOVE_PUD on arm64 : ~19x speed up
> 
>           Altogether, HAVE_MOVE_PMD and HAVE_MOVE_PUD
>           give a total of ~150x speed up on arm64.

Is there a *real* workload that benefit from HAVE_MOVE_PUD?

-- 
 Kirill A. Shutemov