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:

quoted

On Wed, Jul 23, 2014 at 09:52:22AM -0400, Matthew Wilcox wrote:

quoted

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.

quoted

quoted

	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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