On 04/27/2017 at 11:06 AM, Dave Young wrote:
> [snip]
>>>>>
>>>>> static int __init crash_save_vmcoreinfo_init(void)
>>>>> {
>>>>> + /* One page should be enough for VMCOREINFO_BYTES under all archs */
>>>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
>>>> page assumption?
>>>>
>>>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
>>> Yes, I considered this before, but VMCOREINFO_BYTES is also used by
>>> VMCOREINFO_NOTE_SIZE
>>> definition which is exported to sysfs, also some platform has larger page
>>> size(64KB), so
>>> I didn't touch this 4096 value.
>>>
>>> I think I should use kmalloc() to allocate both of them, then move this
>>> comment to Patch3
>>> kimage_crash_copy_vmcoreinfo().
>> But on the other hand, using a separate page for them seems safer compared
>> with
>> using frequently-used slab, what's your opinion?
> I feel current page based way is better.
>
> For 64k page the vmcore note size will increase it seems fine. Do you
> have concern in mind?
Since tools are supposed to acquire vmcoreinfo note size from sysfs, it should
be safe to do so,
except that there is some waste in memory for larger PAGE_SIZE.
Regards,
Xunlei
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