From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: James Morris <jmorris@namei.org>, Sasha Levin <sashal@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
kexec mailing list <kexec@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Catalin Marinas <catalin.marinas@arm.com>,
will@kernel.org,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Marc Zyngier <marc.zyngier@arm.com>,
James Morse <james.morse@arm.com>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
Bhupesh Sharma <bhsharma@redhat.com>
Subject: Re: [RFC v2 0/8] arm64: MMU enabled kexec relocation
Date: Wed, 31 Jul 2019 13:04:08 -0400 [thread overview]
Message-ID: <CA+CK2bBOSC0iYjq_A18DNaNCYskTTJJTkM4N-WAqssoxpxuNPg@mail.gmail.com> (raw)
In-Reply-To: <20190731165007.GJ39768@lakrids.cambridge.arm.com>
On Wed, Jul 31, 2019 at 12:50 PM Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Wed, Jul 31, 2019 at 12:40:51PM -0400, Pavel Tatashin wrote:
> > On Wed, Jul 31, 2019 at 12:33 PM Mark Rutland <mark.rutland@arm.com> wrote:
> > >
> > > Hi Pavel,
> > >
> > > Generally, the cover letter should state up-front what the goal is (or
> > > what problem you're trying to solve). It would be really helpful to have
> > > that so that we understand what you're trying to achieve, and why.
>
> [...]
>
> > > > Here is the current data from the real hardware:
> > > > (because of bug, I forced EL1 mode by setting el2_switch always to zero in
> > > > cpu_soft_restart()):
> > > >
> > > > For this experiment, the size of kernel plus initramfs is 25M. If initramfs
> > > > was larger, than the improvements would be even 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
> > >
> > > In total this takes ~0.76s...
> > >
> > > >
> > > > Relocation was taking: 58.2% of reboot time
> > > >
> > > > Now:
> > > > kernel shutdown 0.032066576s
> > > > relocation 0.022158152s
> > > > kernel startup 0.296055880s
> > >
> > > ... and this takes ~0.35s
> > >
> > > So do we really need this complexity for a few blinks of an eye?
> >
> > Yes, we have an extremely tight reboot budget, 0.35s is not an acceptable waste.
>
> Could you please elaborate on your use-case?
>
> Understanfin what you're trying to achieve would help us to understand
> which solutions make sense.
An extremely high availability device with an update story utilizing
kexec functionality for a faster kernel update and also for being able
to preserve some state in memory without wasting the time of copying
it to and from a backing storage. We at Microsoft will be using a
fleet of these devices. The total reboot budget is less than half a
second, out of which 0.44s is currently spent in kexec relocation.
Pasha
>
> Thanks,
> Mark.
next prev parent reply other threads:[~2019-07-31 17:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 15:38 [RFC v2 0/8] arm64: MMU enabled kexec relocation Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 1/8] kexec: quiet down kexec reboot Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 2/8] arm64, mm: transitional tables Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 3/8] arm64: hibernate: switch to transtional page tables Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 4/8] kexec: add machine_kexec_post_load() Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 5/8] arm64, kexec: move relocation function setup and clean up Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 6/8] arm64, kexec: add expandable argument to relocation function Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 7/8] arm64, kexec: configure transitional page table for kexec Pavel Tatashin
2019-07-31 15:38 ` [RFC v2 8/8] arm64, kexec: enable MMU during kexec relocation Pavel Tatashin
2019-07-31 15:50 ` Mark Rutland
2019-07-31 16:01 ` Pavel Tatashin
2019-07-31 16:32 ` [RFC v2 0/8] arm64: MMU enabled " Mark Rutland
2019-07-31 16:40 ` Pavel Tatashin
2019-07-31 16:50 ` Mark Rutland
2019-07-31 17:04 ` Pavel Tatashin [this message]
2019-08-01 13:24 ` Pavel Tatashin
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