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Date: Wed, 30 Sep 2020 19:03:26 -0400 From: Kalesh Singh <kaleshsingh@...gle.com> To: Joel Fernandes <joelaf@...gle.com> Cc: Lokesh Gidra <lokeshgidra@...gle.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Suren Baghdasaryan <surenb@...gle.com>, Minchan Kim <minchan@...gle.com>, "Cc: Android Kernel" <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>, "the arch/x86 maintainers" <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 <linux-kernel@...r.kernel.org>, "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" <linux-arm-kernel@...ts.infradead.org>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>, "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org> Subject: Re: [PATCH 0/5] Speed up mremap on large regions On Wed, Sep 30, 2020 at 6:47 PM Joel Fernandes <joelaf@...gle.com> wrote: > > On Wed, Sep 30, 2020 at 6:42 PM Lokesh Gidra <lokeshgidra@...gle.com> wrote: > > > > On Wed, Sep 30, 2020 at 3:32 PM Kirill A. Shutemov > > <kirill.shutemov@...ux.intel.com> wrote: > > > > > > 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? > > > > > We have a Java garbage collector under development which requires > > moving physical pages of multi-gigabyte heap using mremap. During this > > move, the application threads have to be paused for correctness. It is > > critical to keep this pause as short as possible to avoid jitters > > during user interaction. This is where HAVE_MOVE_PUD will greatly > > help. > > And that detail should totally have gone into the commit message :-/ Hi Joel, The patch that introduces HAVE_MOVE_PUD in the series mentions the Android garbage collection use case. I can add these details there in the next version. Thanks, Kalesh > > Thanks, > > - Joel
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