Liu Ping Fan <kernelf...@gmail.com> writes:
> The period check of _PAGE_NUMA can probably trigger the check on
> the correctly placed page. For this case, we can just insert hpte and
> do fast exception return.
I still don't understand why we need to handle numa faults in hash
page ? Are you trying to optimize the code path ? If so can you explain
the benefits ? Some numbers showing it is helping ?
>
> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/hash_utils_64.c | 34 +++++++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 9bf1195..735678c 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -965,6 +965,10 @@ int hash_page(unsigned long ea, unsigned long access,
> unsigned long trap)
> const struct cpumask *tmp;
> int rc, user_region = 0, local = 0;
> int psize, ssize;
> + pte_t old, new;
> + struct vm_area_struct *vma;
> + int page_nid, target_nid;
> + struct page *test_page;
>
> DBG_LOW("hash_page(ea=%016lx, access=%lx, trap=%lx\n",
> ea, access, trap);
> @@ -1033,12 +1037,40 @@ int hash_page(unsigned long ea, unsigned long access,
> unsigned long trap)
>
> /* Get PTE and page size from page tables */
> ptep = find_linux_pte_or_hugepte(pgdir, ea, &hugeshift);
> - if (ptep == NULL || !pte_present(*ptep) || pte_numa(*ptep)) {
> + if (ptep == NULL || !pte_present(*ptep)) {
> DBG_LOW(" no PTE !\n");
> rc = 1;
> goto bail;
> }
>
> + old = pte_val(*ptep);
> + if (pte_numa(old)) {
> + /* If fail to lock, let do_page_fault() to handle it */
> + if (down_read_trylock(&mm->mmap_sem)) {
hmm is that something we want to do in hash_page ?
> + vma = find_vma(mm, ea);
> + up_read(&mm->mmap_sem);
> + test_page = pte_page(old);
> + page_nid = page_to_nid(test_page);
> + target_nid = numa_migrate_prep(test_page, vma, ea,
> + page_nid);
> + if (target_nid < 0) {
> + new = pte_mknonnuma(old);
> + /* If ptep is modified under us,
> + * just retry the access
> + */
> + if (unlikely(cmpxchg(ptep, old, new) != old)) {
> + put_page(test_page);
> + return 0;
> + }
> + put_page(test_page);
> + }
> + } else {
> + put_page(test_page);
> + rc = 1;
> + goto bail;
> + }
> + }
> +
> /* Add _PAGE_PRESENT to the required access perm */
> access |= _PAGE_PRESENT;
>
-aneesh
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