Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 2/6] mm: mlocking in try_to_unmap_one | Date | Fri, 13 Nov 2009 17:16:27 +0900 (JST) |
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> On Wed, 11 Nov 2009, KOSAKI Motohiro wrote: > > Though it doesn't quite answer your question, > I'll just reinsert the last paragraph of my description here... > > > > try_to_unmap_file()'s TTU_MUNLOCK nonlinear handling was particularly > > > amusing: once unravelled, it turns out to have been choosing between > > > two different ways of doing the same nothing. Ah, no, one way was > > > actually returning SWAP_FAIL when it meant to return SWAP_SUCCESS. > > ... > > > @@ -1081,45 +1053,23 @@ static int try_to_unmap_file(struct page > ... > > > > > > - if (list_empty(&mapping->i_mmap_nonlinear)) > > > + /* We don't bother to try to find the munlocked page in nonlinears */ > > > + if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK) > > > goto out; > > > > I have dumb question. > > Does this shortcut exiting code makes any behavior change? > > Not dumb. My intention was to make no behaviour change with any of > this patch; but in checking back before completing the description, > I suddenly realized that that shortcut intentionally avoids the > > if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ > ret = SWAP_FAIL; > goto out; > } > > (which doesn't show up in the patch: you'll have to look at rmap.c), > which used to have the effect of try_to_munlock() returning SWAP_FAIL > in the case when there were one or more VM_NONLINEAR vmas of the file, > but none of them (and none of the covering linear vmas) VM_LOCKED. > > That should have been a SWAP_SUCCESS case, or with my changes > another SWAP_AGAIN, either of which would make munlock_vma_page() > count_vm_event(UNEVICTABLE_PGMUNLOCKED); > which would be correct; but the SWAP_FAIL meant that count was not > incremented in this case.
Ah, correct. Then, we lost the capability unevictability of non linear mapping pages, right. if so, following additional patch makes more consistent?
> > Actually, I've double-fixed that, because I also changed > munlock_vma_page() to increment the count whenever ret != SWAP_MLOCK; > which seemed more appropriate, but would have been a no-op if > try_to_munlock() only returned SWAP_SUCCESS or SWAP_AGAIN or SWAP_MLOCK > as it claimed. > > But I wasn't very inclined to boast of fixing that bug, since my testing > didn't give confidence that those /proc/vmstat unevictable_pgs_*lock* > counts are being properly maintained anyway - when I locked the same > pages in two vmas then unlocked them in both, I ended up with mlocked > bigger than munlocked (with or without my 2/6 patch); which I suspect > is wrong, but rather off my present course towards KSM swapping...
Ah, vmstat inconsistent is weird. I'll try to debug it later. Thanks this notice.
---------------------------------- From 3fd3bc58dc6505af73ecf92c981609ecf8b6ac40 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Date: Fri, 13 Nov 2009 16:52:03 +0900 Subject: [PATCH] [RFC] mm: non linear mapping page don't mark as PG_mlocked
Now, try_to_unmap_file() lost the capability to treat VM_NONLINEAR. Then, mlock() shouldn't mark the page of non linear mapping as PG_mlocked. Otherwise the page continue to drinker walk between evictable and unevictable lru.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- mm/mlock.c | 37 +++++++++++++++++++++++-------------- 1 files changed, 23 insertions(+), 14 deletions(-)
diff --git a/mm/mlock.c b/mm/mlock.c index 48691fb..4187f9c 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -266,25 +266,34 @@ long mlock_vma_pages_range(struct vm_area_struct *vma, if (vma->vm_flags & (VM_IO | VM_PFNMAP)) goto no_mlock; - if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) || + if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) || is_vm_hugetlb_page(vma) || - vma == get_gate_vma(current))) { + vma == get_gate_vma(current)) { + + /* + * User mapped kernel pages or huge pages: + * make these pages present to populate the ptes, but + * fall thru' to reset VM_LOCKED--no need to unlock, and + * return nr_pages so these don't get counted against task's + * locked limit. huge pages are already counted against + * locked vm limit. + */ + make_pages_present(start, end); + goto no_mlock; + } + if (vma->vm_flags & VM_NONLINEAR) + /* + * try_to_munmap() doesn't treat VM_NONLINEAR. let's make + * consist. + */ + make_pages_present(start, end); + else __mlock_vma_pages_range(vma, start, end); - /* Hide errors from mmap() and other callers */ - return 0; - } + /* Hide errors from mmap() and other callers */ + return 0; - /* - * User mapped kernel pages or huge pages: - * make these pages present to populate the ptes, but - * fall thru' to reset VM_LOCKED--no need to unlock, and - * return nr_pages so these don't get counted against task's - * locked limit. huge pages are already counted against - * locked vm limit. - */ - make_pages_present(start, end); no_mlock: vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */ -- 1.6.2.5
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