Re: [RFC] mm: why vfree() do not free page table memory?

[Vlastimil Babka]

On 12/29/2017 09:58 AM, Xishi Qiu wrote:
> When calling vfree(), it calls unmap_vmap_area() to clear page table,
> but do not free the memory of page table, why? just for performance?

I guess it's expected that the free virtual range and associated page
tables it might be reused later.

> If a driver use vmalloc() and vfree() frequently, we will lost much
> page table memory, maybe oom later.

If it's reused, then not really.

Did you notice an actual issue, or is this just theoretical concern.

> Thanks,
> Xishi Qiu
>