On Wed, Jul 23, 2014 at 10:27:45AM -0400, Matthew Wilcox wrote:
> On Wed, Jul 23, 2014 at 05:20:48PM +0300, Kirill A. Shutemov wrote:
> > On Wed, Jul 23, 2014 at 09:52:22AM -0400, Matthew Wilcox wrote:
> > > I'd love to use a lighter-weight weapon! What would you recommend using,
> > > zap_pte_range()?
> >
> > The most straight-forward way: extract body of pte cycle from
> > zap_pte_range() to separate function -- zap_pte() -- and use it.
>
> OK, I can do that. What about the other parts of zap_page_range(),
> do I need to call them?
>
> lru_add_drain();
No, I guess..
> tlb_gather_mmu(&tlb, mm, address, end);
> tlb_finish_mmu(&tlb, address, end);
New zap_pte() should tolerate tlb == NULL and does flush_tlb_page() or
pte_clear_*flush or something.
> update_hiwater_rss(mm);
No: you cannot end up with lower rss after replace, iiuc.
> mmu_notifier_invalidate_range_start(mm, address, end);
> mmu_notifier_invalidate_range_end(mm, address, end);
mmu_notifier_invalidate_page() should be enough.
> > > if ((fd = open(argv[1], O_CREAT|O_RDWR, 0666)) < 0) {
> > > perror(argv[1]);
> > > exit(1);
> > > }
> > >
> > > if (ftruncate(fd, 4096) < 0) {
> >
> > Shouldn't this be ftruncate(fd, 0)? Otherwise the memcpy() below will
> > fault in page from backing storage, not hole and write will not replace
> > anything.
>
> Ah, it was starting with a new file, hence the O_CREAT up above.
Do you mean you pointed to new file all the time? O_CREAT doesn't truncate
file if it exists, iirc.
--
Kirill A. Shutemov
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