Messages in this thread | | | Date | Tue, 3 Jan 2006 13:22:38 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: page refcounts? |
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On Thu, 29 Dec 2005, Avishay Traeger wrote:
> How does the kernel determine when a page is unused? I see that > __get_free_pages() returns pages that have no refcount and no flags > indicating that they should not be reclaimed. > > The first page that is returned looks like: > flags:0x80000000 mapping:00000000 mapcount:0 count:1 > > And the subsequent pages look like: > flags:0x80000000 mapping:00000000 mapcount:0 count:0 > > I am printing this out exactly the way bad_page() does. How does the > kernel know not to mess around with pages that have no refcount or any > flags to indicate that they are in use? I've already searched google > and checked a couple books, and couldn't find an answer.
The kernel knows that a page is free if count == 0 in the first page. All pages of a higher order allocation are managed through the status of the first page. - 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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