On Thu, Dec 5, 2013 at 6:58 PM, Aneesh Kumar K.V
aneesh.ku...@linux.vnet.ibm.com wrote:
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 ?
When return from hash_page(), we will take fast_exc_return_irq, while
from do_page_fault(), we take ret_from_except.
As the fast implies that there are more complicated logic to sync
the interrupt states in ret_from_except, which cost much.
Do you think so?
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 ?
Yes, the function has no relation with hash. But I think it depends on
whether it is worth to optimize or not.
Thanks and regards,
Pingfan
+ 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
___
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
