Are there some potential problems that I should be aware of if I allocate the memory which doesn't have any relation to peripheral hardwares(i.e. DMA, PCI, serial port and etc) by vmalloc() instead of kmalloc()?

[Greg KH]

On Fri, Jun 26, 2020 at 11:36:05PM +0800, 孙世龙 sunshilong wrote:
> Thank you for your attention to this matter.
> 
> >Why are you having so many issues in allocating memory?
> I often saw the page allocation failure recently. I must resolve this problem.

What code is causing that failure by asking for memory that you do not
have?  Please fix that up, the core kernel should be fine.

> I have no choice other than disabling these options
> (i.e. CONFIG-MIGRATION and CONFIG-COMPACTION)
> since I am using a real-time OS.

As was already stated, the use of "real-time" has nothing to do with
those options, or memory allocation, or anything else here.  Please do
not get confused about the determinisitic operation of
interrupts/scheduling vs. anything else.

> It's easier to encounter such a problem since the said options are disabled.

Then fix your broken driver that is asking for so much memory on a
system that does not have it.  Do you have a pointer to your driver
anywhere so we can review it?

good luck!

greg k-h