在 2024/7/8 19:02, Barry Song 写道:
On Mon, Jul 8, 2024 at 9:04 PM Zhiguo Jiang <justinjiang@xxxxxxxx> wrote:
The releasing process of the non-shared anonymous folio mapped solely by
an exiting process may go through two flows: 1) the anonymous folio is
firstly is swaped-out into swapspace and transformed into a swp_entry
in shrink_folio_list; 2) then the swp_entry is released in the process
exiting flow. This will increase the cpu load of releasing a non-shared
anonymous folio mapped solely by an exiting process, because the folio
go through swap-out and the releasing the swapspace and swp_entry.
When system is low memory, it is more likely to occur, because more
backend applidatuions will be killed.
The modification is that shrink skips the non-shared anonymous folio
solely mapped by an exting process and the folio is only released
directly in the process exiting flow, which will save swap-out time
and alleviate the load of the process exiting.
Signed-off-by: Zhiguo Jiang <justinjiang@xxxxxxxx>
---
Change log:
v4->v5:
1.Modify to skip non-shared anonymous folio only.
2.Update comments for pra->referenced = -1.
v3->v4:
1.Modify that the unshared folios mapped only in exiting task are skip.
v2->v3:
Nothing.
v1->v2:
1.The VM_EXITING added in v1 patch is removed, because it will fail
to compile in 32-bit system.
mm/rmap.c | 13 +++++++++++++
mm/vmscan.c | 7 ++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 26806b49a86f..5b5281d71dbb
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -843,6 +843,19 @@ static bool folio_referenced_one(struct folio *folio,
int referenced = 0;
unsigned long start = address, ptes = 0;
+ /*
+ * Skip the non-shared anonymous folio mapped solely by
+ * the single exiting process, and release it directly
+ * in the process exiting.
+ */
+ if ((!atomic_read(&vma->vm_mm->mm_users) ||
+ test_bit(MMF_OOM_SKIP, &vma->vm_mm->flags)) &&
+ folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_likely_mapped_shared(folio)) {
+ pra->referenced = -1;
+ return false;
+ }
+
while (page_vma_mapped_walk(&pvmw)) {
address = pvmw.address;
Sure, I agree with your modification suggestions. This way, using PTL
indeed sure
that the folio is mapped by this process.
Thanks
As David suggested, what about the below?
@@ -883,6 +870,21 @@ static bool folio_referenced_one(struct folio *folio,
continue;
}
+ /*
+ * Skip the non-shared anonymous folio mapped solely by
+ * the single exiting process, and release it directly
+ * in the process exiting.
+ */
+ if ((!atomic_read(&vma->vm_mm->mm_users) ||
+ test_bit(MMF_OOM_SKIP,
&vma->vm_mm->flags)) &&
+ folio_test_anon(folio) &&
folio_test_swapbacked(folio) &&
+ !folio_likely_mapped_shared(folio)) {
+ pra->referenced = -1;
+ page_vma_mapped_walk_done(&pvmw);
+ return false;
+ }
+
if (pvmw.pte) {
if (lru_gen_enabled() &&
pte_young(ptep_get(pvmw.pte))) {
By the way, I am not convinced that using test_bit(MMF_OOM_SKIP,
&vma->vm_mm->flags) is
correct (I think it is wrong). For example, global_init can directly have it:
if (is_global_init(p)) {
can_oom_reap = false;
set_bit(MMF_OOM_SKIP, &mm->flags);
pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
task_pid_nr(victim), victim->comm,
task_pid_nr(p), p->comm);
continue;
}
And exit_mmap() automatically has MMF_OOM_SKIP.
What is the purpose of this check? Is there a better way to determine
if a process is an
OOM target? What about check_stable_address_space() ?
1.Sorry, I overlook the situation with if (is_global_init(p)),
MMF_OOM_SKIP is indeed not suitable.
2.check_stable_address_space() can indicate oom_reaper, but it seems
unable to identify the situation where the process exits normally. What
about task_is_dying()? static inline bool task_is_dying(void) { return
tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
(current->flags & PF_EXITING); } Thanks
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0761f91b407f..bae7a8bf6b3d
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -863,7 +863,12 @@ static enum folio_references folio_check_references(struct folio *folio,
if (vm_flags & VM_LOCKED)
return FOLIOREF_ACTIVATE;
- /* rmap lock contention: rotate */
+ /*
+ * There are two cases to consider.
+ * 1) Rmap lock contention: rotate.
+ * 2) Skip the non-shared anonymous folio mapped solely by
+ * the single exiting process.
+ */
if (referenced_ptes == -1)
return FOLIOREF_KEEP;
--
2.39.0
Thanks
Barry
