From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Sasha Levin <sashal@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
Catalin Marinas <catalin.marinas@arm.com>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
kexec mailing list <kexec@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
James Morris <jmorris@namei.org>,
Eric Biederman <ebiederm@xmission.com>,
will@kernel.org,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [v1 0/5] allow to reserve memory for normal kexec kernel
Date: Tue, 9 Jul 2019 06:55:43 -0400 [thread overview]
Message-ID: <CA+CK2bBrwBHhD-PFO_gVnDYoFi0Su6t456WNdtBWpOe4qM+oww@mail.gmail.com> (raw)
In-Reply-To: <CACi5LpNGWhTnXyM8gB0Tn=682+08s-ppfDpX2SawfxMvue1GTQ@mail.gmail.com>
On Tue, Jul 9, 2019 at 6:36 AM Bhupesh Sharma <bhsharma@redhat.com> wrote:
>
> Hi Pavel,
>
> On Tue, Jul 9, 2019 at 2:46 AM Pavel Tatashin <pasha.tatashin@soleen.com> wrote:
> >
> > Currently, it is only allowed to reserve memory for crash kernel, because
> > it is a requirement in order to be able to boot into crash kernel without
> > touching memory of crashed kernel is to have memory reserved.
> >
> > The second benefit for having memory reserved for kexec kernel is
> > that it does not require a relocation after segments are loaded into
> > memory.
> >
> > If kexec functionality is used for a fast system update, with a minimal
> > downtime, the relocation of kernel + initramfs might take a significant
> > portion of reboot.
> >
> > In fact, on the machine that we are using, that has ARM64 processor
> > it takes 0.35s to relocate during kexec, thus taking 52% of kernel reboot
> > time:
> >
> > kernel shutdown 0.03s
> > relocation 0.35s
> > kernel startup 0.29s
> >
> > Image: 13M and initramfs is 24M. If initramfs increases, the relocation
> > time increases proportionally.
> >
> > While, it is possible to add 'kexeckernel=' parameters support to other
> > architectures by modifying reserve_crashkernel(), in this series this is
> > done for arm64 only.
> >
> > Pavel Tatashin (5):
> > kexec: quiet down kexec reboot
> > kexec: add resource for normal kexec region
> > kexec: export common crashkernel/kexeckernel parser
> > kexec: use reserved memory for normal kexec reboot
> > arm64, kexec: reserve kexeckernel region
> >
> > .../admin-guide/kernel-parameters.txt | 7 ++
> > arch/arm64/kernel/setup.c | 5 ++
> > arch/arm64/mm/init.c | 83 ++++++++++++-------
> > include/linux/crash_core.h | 6 ++
> > include/linux/ioport.h | 1 +
> > include/linux/kexec.h | 6 +-
> > kernel/crash_core.c | 27 +++---
> > kernel/kexec_core.c | 50 +++++++----
> > 8 files changed, 127 insertions(+), 58 deletions(-)
> >
> > --
> > 2.22.0
>
> This seems like an issue with time spent while doing sha256
> verification while in purgatory.
>
> Can you please try the following two patches which enable D-cache in
> purgatory before SHA verification and disable it before switching to
> kernel:
>
> http://lists.infradead.org/pipermail/kexec/2017-May/018839.html
> http://lists.infradead.org/pipermail/kexec/2017-May/018840.html
Hi Bhupesh,
The verification was taking 2.31s. This is why it is disabled via
kexec's '-i' flag. Therefore 0.35s is only the relocation part where
time is spent, and with my patches the time is completely gone.
Actually, I am glad you showed these patches to me because I might
pull them and enable verification for our needs.
>
> Note that these were not accepted upstream but are included in several
> distros in some form or the other :)
Enabling MMU and D-Cache for relocation would essentially require the
same changes in kernel. Could you please share exactly why these were
not accepted upstream into kexec-tools?
Thank you,
Pasha
>
> Thanks,
> Bhupesh
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next prev parent reply other threads:[~2019-07-09 10:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 21:15 [v1 0/5] allow to reserve memory for normal kexec kernel Pavel Tatashin
2019-07-08 21:15 ` [v1 1/5] kexec: quiet down kexec reboot Pavel Tatashin
2019-07-08 21:15 ` [v1 2/5] kexec: add resource for normal kexec region Pavel Tatashin
2019-07-08 21:15 ` [v1 3/5] kexec: export common crashkernel/kexeckernel parser Pavel Tatashin
2019-07-08 21:15 ` [v1 4/5] kexec: use reserved memory for normal kexec reboot Pavel Tatashin
2019-07-08 21:15 ` [v1 5/5] arm64, kexec: reserve kexeckernel region Pavel Tatashin
2019-07-08 23:53 ` [v1 0/5] allow to reserve memory for normal kexec kernel Eric W. Biederman
2019-07-09 0:09 ` Pavel Tatashin
2019-07-09 10:18 ` James Morse
2019-07-09 10:36 ` Bhupesh Sharma
2019-07-09 10:55 ` Pavel Tatashin [this message]
2019-07-09 11:59 ` James Morse
2019-07-09 13:07 ` Pavel Tatashin
2019-07-10 15:19 ` James Morse
2019-07-10 15:56 ` Pavel Tatashin
2019-07-11 8:12 ` Vladimir Murzin
2019-07-11 12:26 ` Pavel Tatashin
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