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tools/vm/page-types.c: support KPF_SOFTDIRTY bit

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Soft dirty bit allows us to track which pages are written since the last
clear_ref (by "echo 4 > /proc/pid/clear_refs".) This is useful for
userspace applications to know their memory footprints.

Note that the kernel exposes this flag via bit[55] of /proc/pid/pagemap,
and the semantics is not a default one (scheduled to be the default in the
near future.) However, it shifts to the new semantics at the first
clear_ref, and the users of soft dirty bit always do it before utilizing
the bit, so that's not a big deal.  Users must avoid relying on the bit in
page-types before the first clear_ref.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Naoya Horiguchi 2013-11-12 15:07:50 -08:00 • committed by Linus Torvalds
parent ec8e41aec1
commit 46c77e2bb0
2 changed files with 21 additions and 12 deletions
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1
include/linux/kernel-page-flags.h
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@ -15,5 +15,6 @@
#define KPF_OWNER_PRIVATE 37
#define KPF_ARCH 38
#define KPF_UNCACHED 39
#define KPF_SOFTDIRTY 40
#endif /* LINUX_KERNEL_PAGE_FLAGS_H */