On 28 Apr 2025, at 14:29, Nico Pache wrote:
> Now that we have defer to globally disable THPs at fault time, lets add
> a defer setting to the mTHP options. This will allow khugepaged to
> operate at that order, while avoiding it at PF time.
>
> Signed-off-by: Nico Pache <npache@xxxxxxxxxx>
> ---
> include/linux/huge_mm.h | 5 +++++
> mm/huge_memory.c | 38 +++++++++++++++++++++++++++++++++-----
> mm/khugepaged.c | 8 ++++----
> 3 files changed, 42 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 57e6c962afb1..a877c59bea67 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -96,6 +96,7 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr;
> #define TVA_SMAPS (1 << 0) /* Will be used for procfs */
> #define TVA_IN_PF (1 << 1) /* Page fault handler */
> #define TVA_ENFORCE_SYSFS (1 << 2) /* Obey sysfs configuration */
> +#define TVA_IN_KHUGEPAGE ((1 << 2) | (1 << 3)) /* Khugepaged defer support */
Why is TVA_IN_KHUGEPAGE a superset of TVA_ENFORCE_SYSFS? Because khugepaged
also obeys sysfs configuration?
I wonder if explicitly coding the behavior is better. For example,
in __thp_vma_allowable_orders(), enforce_sysfs = tva_flags & (TVA_ENFORCE_SYSFS | TVA_IN_KHUGEPAGE).
>
> #define thp_vma_allowable_order(vma, vm_flags, tva_flags, order) \
> (!!thp_vma_allowable_orders(vma, vm_flags, tva_flags, BIT(order)))
> @@ -182,6 +183,7 @@ extern unsigned long transparent_hugepage_flags;
> extern unsigned long huge_anon_orders_always;
> extern unsigned long huge_anon_orders_madvise;
> extern unsigned long huge_anon_orders_inherit;
> +extern unsigned long huge_anon_orders_defer;
>
> static inline bool hugepage_global_enabled(void)
> {
> @@ -306,6 +308,9 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
> /* Optimization to check if required orders are enabled early. */
> if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) {
And code here becomes tva_flags & (TVA_ENFORCE_SYSFS | TVA_IN_KHUGEPAGE).
Otherwise, LGTM. Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
--
Best Regards,
Yan, Zi
