On Tue, Jul 9, 2019 at 6:36 AM Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote: > > Hi Pavel, > > On Tue, Jul 9, 2019 at 2:46 AM Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> 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
