Messages in this thread | | | Date | Thu, 3 Mar 2022 09:31:40 -0600 | Subject | Re: [PATCH v4 02/10] crash hp: Introduce CRASH_HOTPLUG configuration options | From | Eric DeVolder <> |
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On 3/3/22 06:08, Baoquan He wrote: > On 03/03/22 at 12:36pm, David Hildenbrand wrote: >> On 03.03.22 11:22, Baoquan He wrote: >>> On 03/02/22 at 10:20am, David Hildenbrand wrote: >>>> On 01.03.22 21:04, Eric DeVolder wrote: >>>>> >>>>> >>>>> On 2/22/22 21:25, Baoquan He wrote: >>>>>> On 02/09/22 at 02:56pm, Eric DeVolder wrote: >>>>>>> Support for CPU and memory hotplug for crash is controlled by the >>>>>>> CRASH_HOTPLUG configuration option, introduced by this patch. >>>>>>> >>>>>>> The CRASH_HOTPLUG_ELFCOREHDR_SZ related configuration option is >>>>>>> also introduced with this patch. >>>>>>> >>>>>>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> >>>>>>> --- >>>>>>> arch/x86/Kconfig | 26 ++++++++++++++++++++++++++ >>>>>>> 1 file changed, 26 insertions(+) >>>>>>> >>>>>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>>>>>> index ebe8fc76949a..4e3374edab02 100644 >>>>>>> --- a/arch/x86/Kconfig >>>>>>> +++ b/arch/x86/Kconfig >>>>>>> @@ -2060,6 +2060,32 @@ config CRASH_DUMP >>>>>>> (CONFIG_RELOCATABLE=y). >>>>>>> For more details see Documentation/admin-guide/kdump/kdump.rst >>>>>>> >>>>>>> +config CRASH_HOTPLUG >>>>>>> + bool "kernel updates of crash elfcorehdr" >>>>>>> + depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) && KEXEC_FILE >>>>>>> + help >>>>>>> + Enable the kernel to update the crash elfcorehdr (which contains >>>>>>> + the list of CPUs and memory regions) directly when hot plug/unplug >>>>>>> + of CPUs or memory. Otherwise userspace must monitor these hot >>>>>>> + plug/unplug change notifications via udev in order to >>>>>>> + unload-then-reload the crash kernel so that the list of CPUs and >>>>>>> + memory regions is kept up-to-date. Note that the udev CPU and >>>>>>> + memory change notifications still occur (however, userspace is not >>>>>>> + required to monitor for crash dump purposes). >>>>>>> + >>>>>>> +config CRASH_HOTPLUG_ELFCOREHDR_SZ >>>>>>> + depends on CRASH_HOTPLUG >>>>>>> + int >>>>>>> + default 131072 >>>>>>> + help >>>>>>> + Specify the maximum size of the elfcorehdr buffer/segment. >>>>>>> + The 128KiB default is sized so that it can accommodate 2048 >>>>>>> + Elf64_Phdr, where each Phdr represents either a CPU or a >>>>>>> + region of memory. >>>>>>> + For example, this size can accommodate hotplugging a machine >>>>>>> + with up to 1024 CPUs and up to 1024 memory regions (e.g. 1TiB >>>>>>> + with 1024 1GiB memory DIMMs). >>>>>> >>>>>> This example of memory could be a little misleading. The memory regions >>>>>> may not be related to memory DIMMs. System could split them into many >>>>>> smaller regions during bootup. >>>>> >>>>> I changed "with 1024 1GiB memory DIMMs" to "with 1024 1GiB hotplug memories". >>>>> eric >>>> >>>> It's still not quite precise. Essentially it's the individual "System >>>> RAM" entries in /proc/iomem >>>> >>>> Boot memory (i.e., a single DIMM) might be represented by multiple >>>> entries due to rearranged holes (by the BIOS). >>>> >>>> While hoplugged DIMMs (under virt!) are usually represented using a >>>> single range, it can be different on physical machines. Last but not >>>> least, dax/kmem and virtio-mem behave in a different way. >>> >>> Right. How about only mentioning the 'System RAM' entries in /proc/iomem >>> as below? It's just giving an example, talking about the details of >>> memory regions from each type may not be necessry here. People >>> interested can refer to code or document related to get it. >>> >>> >>> + default 131072 >>> + help >>> + Specify the maximum size of the elfcorehdr buffer/segment. >>> + The 128KiB default is sized so that it can accommodate 2048 >>> + Elf64_Phdr, where each Phdr represents either a CPU or a >>> + region of memory. >>> + For example, this size can accommodate hotplugging a machine >>> + with up to 1024 CPUs and up to 1024 memory regions which are >>> represented by 'System RAM' entries in /proc/iomem. >> >> Maybe changing the last paragraph to: >> >> "For example, this size can accommodate a machine with up to 1024 CPUs >> and up to 1024 memory regions, for example, as represented by 'System >> RAM' entries in /proc/iomem." > > Yeah, this looks good. Can the 2nd 'for example' be removed or replaced > with 'e.g'? Please ignore it if it's normal to have two 'for example' in > one sentence, just gentlely ask. > Great, I will make the change to the text as agreed upon here! eric
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