Messages in this thread | | | Date | Fri, 22 Jul 2022 19:37:19 +0800 | Subject | Re: [PATCH 0/2] kexec: accumulate and release the size of crashkernel | From | Carlo Bai <> |
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On 2022/7/5 9:56, Baoquan He wrote: > On 07/04/22 at 07:41pm, Kaihao Bai wrote: >> Currently x86 and arm64 support to reserve low memory range for >> crashkernel. When crashkernel=Y,low is defined, the main kernel would >> reserve another memblock (instead of crashkernel=X,high, which stored >> in crashk_res) for crashkernel and store it in crashk_low_res. >> >> The implementations of get_crash_size and crash_shrink_size do not >> consider the extra reserved memory range if it exists. Thus, firstly >> accumulate this range on the size of crashkernel and export the size >> by /sys/kernel/kexec_crash_size. >> >> If getting the input of /sys/kernel/kexec_crash_size, both reserved ranges >> might be released if the new size is smaller than current size. The order >> of release is (crashk_res -> crashk_low_res). Only if the new size defined >> by the user is smaller than the size of low memory range, continue to >> release the reserved low memory range after completely releasing the high >> memory range. > > Sorry, I don't like this patchset. > > I bet you don't encounter a real problem in your product environment. > Regarding crashkernel=,high|low, the ,low memory is for DMA and > requirement from memory under lower range. The ,high meomry is for > kernel/initrd loading, kernel data, user space program running. When > you configure crashkernel= in your system, you need evaluate what > value is suitable. /sys/kernel/kexec_crash_size is an interface you > can make use of to tune the memory usage. People are not suggested to > free all crashkernel reservation via the interface. > > So, please leave this as is, unless you have a real case where this > change is needed. > > Thanks > Baoquan
Sorry for the late reply.
Sincerely thanks for your reviewing, I don't have a real problem which needs to release part/all of the reserved low memory range of crashkernel. All I think is to change the interface more compatible with the reserved low memory range.
Besides, I think it's still confusing if we have actually reserved low memory range of crashkernel, but it does not reflect by the size of kexec_crash_size.
Thanks, Kaihao Bai
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