Hello Baoquan,
Hi,
On 02/21/22 at 02:16pm, Sourabh Jain wrote:
On hotplug event (CPU/memory) the CPU information prepared for the kdump kernel
becomes stale unless it is prepared again. To keep the CPU information
up-to-date a kdump service reload is triggered via the udev rule.
The above approach has two downsides:
1) The udev rules are prone to races if hotplug event is frequent. The time is
taken to settle down all the kdump service reload requested is significant
when multiple CPU/memory hotplug is performed at the same time. This creates
a window where kernel crash might not lead to successfully dump collection.
2) Unnecessary CPU cycles are consumed to reload all the kdump components
including initrd, vmlinux, FDT, etc. whereas only one component needs to
update that is FDT.
I roughly went through this sereis, while haven't read the code
carefully. Seems the issue and the approach are similar to what below
patchset is doing. Do you notice below patchset from Oracle engineer?
And is there stuff the ppc code can be rebased on and reused?
[PATCH v4 00/10] crash: Kernel handling of CPU and memory hot un/plug
https://lore.kernel.org/all/20220209195706.51522-1-eric.devolder@xxxxxxxxxx/T/#u
Thanks for the suggestion. I have seen earlier versions of this patch series
but since it did not have support for kexec_load system call we tried
implementing
something from scratch.
Since Eric's added support for kexec_load and has a generic handler for
CPU and
memory hotplug let me see if I can rebase my PowerPC changes on top of
his patches.
The major difference across the distro is that on PowerPC we need to
update FDT instead
of elfcorehdr on hotplug event.
Thanks,
Sourabh Jain
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