zhiguojiang 于 2024年7月9日周二 00:25写道： > > > 在 2024/7/8 20:17, zhiguojiang 写道: > > > > > > 在 2024/7/8 19:02, Barry Song 写道: > >> On Mon, Jul 8, 2024 at 9:04 PM Zhiguo Jiang > >> 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 > >>> --- > >>> > >>> 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 > We can migrate task_is_dying() from mm/memcontrol.c to include/linux/oom.h > > static inline bool task_is_dying(void) > > { > > return tsk_is_oom_victim(current) || fatal_signal_pending(current) || > > (current->flags & PF_EXITING); > > } > no. current is kswapd. > >> > >> > >>> 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 > > > >