On Jul 13, 2022, at 1:26 PM, Peter Zijlstra [off-list ref] wrote:

On Wed, Jul 13, 2022 at 03:48:35PM +0000, Song Liu wrote:

quoted

quoted

So how about instead we separate them? Then much of the problem goes
away, you don't need to track these 2M chunks at all.

If we manage the memory in < 2MiB granularity, either 4kB or smaller, 
we still need some way to track which parts are being used, no? I mean
the bitmap.  

I was thinking the vmalloc vmap_area tree could help out there.

Interesting. vmap_area tree indeed keeps a lot of useful information. 

Currently, powerpc supports CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC, 
which leaves module_alloc just for module text. If this works, we get
separation between RO+X and RW memory. What would it take to enable
CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC for x86_64? 

Thanks,
Song