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p0mlcuN41np50wQ5ru/zCQ4A57JKK63ViZOsPHt2gKD892eyqjlhsKjuuJriwQT4hix48PYs/qXa4qgROu0gmTgiqbec96IBfQGuyQ5h4MVGT3tkk7LIJ4LUE2z18BO7a2K9C0C1rwfJ9f54byrlVOa2Z73h4mRWyvU8XzwDFptWYYhqcw+qyf5VPgGvQSiDbnmabeTkyiqTwSNBGTYElAqkfGSGXUi08mSyUqCPzaIRjfbXmeT+hY+aViaCF0v4cF0bNh8iBJi9Ts6cQ+c1CFTCKlZC047s4/EqK1h27iLT+61O63z1dPWVxv07um+UqyPrVhPGg7druT8Crkqbo3JXkKiRulSHjzdZNEKmBTONuQIuxbRB+cLXxZw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2024/7/8 20:41, Barry Song 写道: > > > 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. Hi Barry, It seems feasible for check_stable_address_space() replacing MMF_OOM_SKIP. check_stable_address_space() can indicate oom kill, and !atomic_read(&vma->vm_mm->mm_users) can indicate the normal process exiting.         /*          * 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) ||             check_stable_address_space(vma->vm_mm)) &&             folio_test_anon(folio) && folio_test_swapbacked(folio) &&             !folio_likely_mapped_shared(folio)) {             pra->referenced = -1;             page_vma_mapped_walk_done(&pvmw);             return false;         } Thanks Zhiguo > > > >> > >> > >>> 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 > > >