Messages in this thread | | | Date | Wed, 13 May 2015 13:59:41 +0300 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH v2 1/3] pagemap: add mmap-exclusive bit for marking pages mapped only here |
| |
On 12.05.2015 13:40, Kirill A. Shutemov wrote: > On Tue, May 12, 2015 at 12:43:03PM +0300, Konstantin Khlebnikov wrote: >> This patch sets bit 56 in pagemap if this page is mapped only once. >> It allows to detect exclusively used pages without exposing PFN: >> >> present file exclusive state >> 0 0 0 non-present >> 1 1 0 file page mapped somewhere else >> 1 1 1 file page mapped only here >> 1 0 0 anon non-CoWed page (shared with parent/child) >> 1 0 1 anon CoWed page (or never forked) > > Probably, worth noting that file-private pages are anon in this context. >
You mean there's another kind of CoW pages? Yep, but from the kernel point of view these pages are the same. Anyway Userspace could look into /proc/*/maps and see is there any file beyond anon vma.
-- Konstantin
| |