Re: [PATCH] mm: add statistics for PUD level pagetable

[Vishal Moola]

On Mon, Sep 18, 2023 at 02:31:42PM +0800, Baolin Wang wrote:
> Recently, we found that cross-die access to pagetable pages on ARM64
> machines can cause performance fluctuations in our business. Currently,
> there are no PMU events available to track this situation on our ARM64
> machines, so an accurate pagetable accounting can help to analyze this
> issue, but now the PUD level pagetable accounting is missed.
> 
> So introducing pagetable_pud_ctor/dtor() to help to get an accurate
> PUD pagetable accounting, as well as converting the architectures with
> using generic PUD pagatable allocation to add corresponding PUD pagetable
> accounting. Moreover this patch will also mark the PUD level pagetable
> with PG_table flag, which will help to do sanity validation in unpoison_memory().
> 
> On my testing machine, I can see more pagetables statistics after the patch
> with page-types tool:
> 
> Before patch:
>         flags           page-count      MB  symbolic-flags                     long-symbolic-flags
> 0x0000000004000000           27326      106  __________________________g_________________       pgtable
> After patch:
> 0x0000000004000000           27541      107  __________________________g_________________       pgtable
> 
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Acked-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>