Hi Matthew,
On 2024/2/5 02:51, Matthew Wilcox wrote:
On Thu, Feb 01, 2024 at 04:05:40PM +0800, Qi Zheng wrote:
For kernel PTE page, we do not need to allocate and initialize its split
ptlock, but as a page table page, it's still necessary to add PG_table
flag and NR_PAGETABLE statistics for it.
No, this is wrong.
We do not account _kernel_ page tables to the _user_. Just because
the kernel, say, called vmalloc() doesn't mean we should charge the
task for it. Moreover, one task may call vmalloc() and a different task
would then call vfree().
Got it. Thanks for providing this information!
This is a can of worms you don't want to open. Why did you want to do
this?
Ah, just because generic {pmd|pud}_alloc_one() has opened it. ;) And
When I looked through the commits (e.g. commit 1d40a5ea01d5), I couldn't
find the information you provided above. And that is why I CC'd you to
double check this, in case I might have overlooked some important
background information.
So we should actually fix generic {pmd|pud}_alloc_one() (and maybe some
implementation in the arch), right? And it would be better to add some
comments to clarify.
Thanks.
