Messages in this thread | | | Date | Mon, 20 Jun 2005 01:45:04 -0400 | From | Mauricio Lin <> | Subject | How to identify cow (copy-on-write) pages during kernel execution? |
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Hi all,
I would like to know if there is a way to identify struct page that is cow (copy-on-write).
The way I figured out to identify cow pages is when copy-on-write happens. I mean I identify cow pages inside the do_wp_page(), the function that handles copy-on-write. I have checked do_no_page() as well.
I have included a field (is_cow) in the struct page to identify cow page.
struct page { ... atomic_t is_cow; }
But I wonder if it is possible to identify cow pages before copy-on-write happens. So identify cow pages in advance before any process tries to write to a cow page.
I have checked the do_fork(), copy_process() and copy_mm() function to try to identify cow pages during the process creation, but no success. In copy_mm(), just the mm (of current process) is provided to the child process, but there are no references to struct pages related to mm and its VMAs.
So when a page struct is considered a cow in the kernel and its count variable is updated? Certainly the counter page (page->_count) is updated when a page is shared because of copy-on-write feature. How can I identify cow pages when it becomes cow? Is there any feasible way to perform that?
BR,
Mauricio Lin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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