Re: [PATCH v4 15/20] powerpc/mm: Avoid useless lock with single page fragments

[Aneesh Kumar K.V]

On 9/18/18 10:27 PM, Christophe Leroy wrote:
> There is no point in taking the page table lock as
> pte_frag is always NULL when we have only one fragment.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
>   arch/powerpc/mm/pgtable-frag.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
> index bc924822dcd6..ab4910e92aaf 100644
> --- a/arch/powerpc/mm/pgtable-frag.c
> +++ b/arch/powerpc/mm/pgtable-frag.c
> @@ -85,6 +85,9 @@ static pte_t *get_pte_from_cache(struct mm_struct *mm)
>   {
>   	void *pte_frag, *ret;
>
> +	if (PTE_FRAG_NR == 1)
> +		return NULL;
> +
>   	spin_lock(&mm->page_table_lock);
>   	ret = mm->context.pte_frag;
>   	if (ret) {

May be update get_pmd_from_cache too?

-aneesh