Messages in this thread | | | Date | Tue, 24 Jun 2008 02:15:06 +0800 | From | "Jeff Chua" <> | Subject | Re: [patch 2/5] Reinstate ZERO_PAGE optimization in get_user_pages() and fix XIP |
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On Tue, Jun 24, 2008 at 1:27 AM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On the other hand, if you add a trace to the "use_zero_page()" function to > print out the vm_flags and other details, that probably would help.
Let me know if you still want me to test this.
> That said, since the previous patch _did_ work, I bet that one that does > both VM_LOCKED and VM_SHARED works too. There was a reason I wanted > to do that VM_SHARED test. I think the VM_SHARED test is sane, unlike the > VM_LOCKED test (that is a fairly dubious hack for mlock). > So here's the final version. I bet it works.
Yeh, it works great! Thank you.
Jeff.
> mm/memory.c | 23 +++++++++++++++++++++-- > 1 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 9aefaae..423e0e7 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1045,6 +1045,26 @@ no_page_table: > return page; > } > > +/* Can we do the FOLL_ANON optimization? */ > +static inline int use_zero_page(struct vm_area_struct *vma) > +{ > + /* > + * We don't want to optimize FOLL_ANON for make_pages_present() > + * when it tries to page in a VM_LOCKED region. As to VM_SHARED, > + * we want to get the page from the page tables to make sure > + * that we serialize and update with any other user of that > + * mapping. > + */ > + if (vma->vm_flags & (VM_LOCKED | VM_SHARED)) > + return 0; > + /* > + * And if we have a fault or a nopfn routine, it's not an > + * anonymous region. > + */ > + return !vma->vm_ops || > + (!vma->vm_ops->fault && !vma->vm_ops->nopfn); > +} > + > int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > unsigned long start, int len, int write, int force, > struct page **pages, struct vm_area_struct **vmas) > @@ -1119,8 +1139,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > foll_flags = FOLL_TOUCH; > if (pages) > foll_flags |= FOLL_GET; > - if (!write && !(vma->vm_flags & VM_LOCKED) && > - (!vma->vm_ops || !vma->vm_ops->fault)) > + if (!write && use_zero_page(vma)) > foll_flags |= FOLL_ANON; > > do { >
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