linux-kernel - Re: [PATCH v1 0/8] arm64: MMU enabled kexec relocation

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Message-ID: <CA+CK2bD6e2WGxuPG+jX8c_qyHNZOC=8NZ-wVZXQuMS2ncBNndg@mail.gmail.com>
Date:   Thu, 15 Aug 2019 13:16:20 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>,
        James Morris <jmorris@...ei.org>,
        Sasha Levin <sashal@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        kexec mailing list <kexec@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>, will@...nel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <marc.zyngier@....com>,
        James Morse <james.morse@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v1 0/8] arm64: MMU enabled kexec relocation

Hi,

It is been two weeks, and no review activity yet. Please help with
reviewing this work.

Thank you,
Pasha

On Thu, Aug 8, 2019 at 2:44 PM Pavel Tatashin <pasha.tatashin@...een.com> wrote:
>
> Just a friendly reminder, please send your comments on this series.
> It's been a week since I sent out these patches, and no feedback yet.
> Also, I'd appreciate if anyone could test this series on vhe hardware
> with vhe kernel, it does not look like QEMU can emulate it yet
>
> Thank you,
> Pasha
>
> On Thu, Aug 1, 2019 at 11:24 AM Pavel Tatashin
> <pasha.tatashin@...een.com> wrote:
> >
> > Enable MMU during kexec relocation in order to improve reboot performance.
> >
> > If kexec functionality is used for a fast system update, with a minimal
> > downtime, the relocation of kernel + initramfs takes a significant portion
> > of reboot.
> >
> > The reason for slow relocation is because it is done without MMU, and thus
> > not benefiting from D-Cache.
> >
> > Performance data
> > ----------------
> > For this experiment, the size of kernel plus initramfs is small, only 25M.
> > If initramfs was larger, than the improvements would be greater, as time
> > spent in relocation is proportional to the size of relocation.
> >
> > Previously:
> > kernel shutdown 0.022131328s
> > relocation      0.440510736s
> > kernel startup  0.294706768s
> >
> > Relocation was taking: 58.2% of reboot time
> >
> > Now:
> > kernel shutdown 0.032066576s
> > relocation      0.022158152s
> > kernel startup  0.296055880s
> >
> > Now: Relocation takes 6.3% of reboot time
> >
> > Total reboot is x2.16 times faster.
> >
> > Previous approaches and discussions
> > -----------------------------------
> > https://lore.kernel.org/lkml/20190709182014.16052-1-pasha.tatashin@soleen.com
> > reserve space for kexec to avoid relocation, involves changes to generic code
> > to optimize a problem that exists on arm64 only:
> >
> > https://lore.kernel.org/lkml/20190716165641.6990-1-pasha.tatashin@soleen.com
> > The first attempt to enable MMU, some bugs that prevented performance
> > improvement. The page tables unnecessary configured idmap for the whole
> > physical space.
> >
> > https://lore.kernel.org/lkml/20190731153857.4045-1-pasha.tatashin@soleen.com
> > No linear copy, bug with EL2 reboots.
> >
> > Pavel Tatashin (8):
> >   kexec: quiet down kexec reboot
> >   arm64, mm: transitional tables
> >   arm64: hibernate: switch to transtional page tables.
> >   kexec: add machine_kexec_post_load()
> >   arm64, kexec: move relocation function setup and clean up
> >   arm64, kexec: add expandable argument to relocation function
> >   arm64, kexec: configure transitional page table for kexec
> >   arm64, kexec: enable MMU during kexec relocation
> >
> >  arch/arm64/Kconfig                     |   4 +
> >  arch/arm64/include/asm/kexec.h         |  51 ++++-
> >  arch/arm64/include/asm/pgtable-hwdef.h |   1 +
> >  arch/arm64/include/asm/trans_table.h   |  68 ++++++
> >  arch/arm64/kernel/asm-offsets.c        |  14 ++
> >  arch/arm64/kernel/cpu-reset.S          |   4 +-
> >  arch/arm64/kernel/cpu-reset.h          |   8 +-
> >  arch/arm64/kernel/hibernate.c          | 261 ++++++-----------------
> >  arch/arm64/kernel/machine_kexec.c      | 199 ++++++++++++++----
> >  arch/arm64/kernel/relocate_kernel.S    | 196 +++++++++---------
> >  arch/arm64/mm/Makefile                 |   1 +
> >  arch/arm64/mm/trans_table.c            | 273 +++++++++++++++++++++++++
> >  kernel/kexec.c                         |   4 +
> >  kernel/kexec_core.c                    |   8 +-
> >  kernel/kexec_file.c                    |   4 +
> >  kernel/kexec_internal.h                |   2 +
> >  16 files changed, 758 insertions(+), 340 deletions(-)
> >  create mode 100644 arch/arm64/include/asm/trans_table.h
> >  create mode 100644 arch/arm64/mm/trans_table.c
> >
> > --
> > 2.22.0
> >