Commit 1c676e0d authored by SeongJae Park's avatar SeongJae Park Committed by Linus Torvalds
Browse files

mm/idle_page_tracking: make PG_idle reusable 

PG_idle and PG_young allow the two PTE Accessed bit users, Idle Page
Tracking and the reclaim logic concurrently work while not interfering
with each other.  That is, when they need to clear the Accessed bit, they
set PG_young to represent the previous state of the bit, respectively.
And when they need to read the bit, if the bit is cleared, they further
read the PG_young to know whether the other has cleared the bit meanwhile
or not.

For yet another user of the PTE Accessed bit, we could add another page
flag, or extend the mechanism to use the flags.  For the DAMON usecase,
however, we don't need to do that just yet.  IDLE_PAGE_TRACKING and DAMON
are mutually exclusive, so there's only ever going to be one user of the
current set of flags.

In this commit, we split out the CONFIG options to allow for the use of
PG_young and PG_idle outside of idle page tracking.

In the next commit, DAMON's reference implementation of the virtual memory
address space monitoring primitives will use it.

[sjpark@amazon.de: set PAGE_EXTENSION for non-64BIT]
  Link: https://lkml.kernel.org/r/20210806095153.6444-1-sj38.park@gmail.com
[akpm@linux-foundation.org: tweak Kconfig text]
[sjpark@amazon.de: hide PAGE_IDLE_FLAG from users]
  Link: https://lkml.kernel.org/r/20210813081238.34705-1-sj38.park@gmail.com

Link: https://lkml.kernel.org/r/20210716081449.22187-5-sj38.park@gmail.com


Signed-off-by: default avatarSeongJae Park <sjpark@amazon.de>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarFernand Sieber <sieberf@amazon.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b9a6ac4e

include/linux/page-flags.h

+2 −2
Original line number Diff line number Diff line
@@ -131,7 +131,7 @@ enum pageflags { 
#ifdef CONFIG_MEMORY_FAILURE

	PG_hwpoison,		/* hardware poisoned page. Don't touch */

#endif

#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)

#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)

	PG_young,

	PG_idle,

#endif
@@ -441,7 +441,7 @@ PAGEFLAG_FALSE(HWPoison) 
#define __PG_HWPOISON 0

#endif



#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)

#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)

TESTPAGEFLAG(Young, young, PF_ANY)

SETPAGEFLAG(Young, young, PF_ANY)

TESTCLEARFLAG(Young, young, PF_ANY)

include/linux/page_ext.h

+1 −1
Original line number Diff line number Diff line
@@ -19,7 +19,7 @@ struct page_ext_operations { 
enum page_ext_flags {

	PAGE_EXT_OWNER,

	PAGE_EXT_OWNER_ALLOCATED,

#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)

#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)

	PAGE_EXT_YOUNG,

	PAGE_EXT_IDLE,

#endif

include/linux/page_idle.h

+3 −3
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ 
#include <linux/page-flags.h>

#include <linux/page_ext.h>



#ifdef CONFIG_IDLE_PAGE_TRACKING

#ifdef CONFIG_PAGE_IDLE_FLAG



#ifdef CONFIG_64BIT

static inline bool page_is_young(struct page *page)
@@ -106,7 +106,7 @@ static inline void clear_page_idle(struct page *page) 
}

#endif /* CONFIG_64BIT */



#else /* !CONFIG_IDLE_PAGE_TRACKING */

#else /* !CONFIG_PAGE_IDLE_FLAG */



static inline bool page_is_young(struct page *page)

{
@@ -135,6 +135,6 @@ static inline void clear_page_idle(struct page *page) 
{

}



#endif /* CONFIG_IDLE_PAGE_TRACKING */

#endif /* CONFIG_PAGE_IDLE_FLAG */



#endif /* _LINUX_MM_PAGE_IDLE_H */

include/trace/events/mmflags.h

+1 −1
Original line number Diff line number Diff line
@@ -75,7 +75,7 @@ 
#define IF_HAVE_PG_HWPOISON(flag,string)

#endif



#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)

#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)

#define IF_HAVE_PG_IDLE(flag,string) ,{1UL << flag, string}

#else

#define IF_HAVE_PG_IDLE(flag,string)

mm/Kconfig

+9 −1
Original line number Diff line number Diff line
@@ -739,10 +739,18 @@ config DEFERRED_STRUCT_PAGE_INIT 
	  lifetime of the system until these kthreads finish the

	  initialisation.



config PAGE_IDLE_FLAG

	bool

	select PAGE_EXTENSION if !64BIT

	help

	  This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed

	  bit writers can set the state of the bit in the flags so that PTE

	  Accessed bit readers may avoid disturbance.



config IDLE_PAGE_TRACKING

	bool "Enable idle page tracking"

	depends on SYSFS && MMU

	select PAGE_EXTENSION if !64BIT

	select PAGE_IDLE_FLAG

	help

	  This feature allows to estimate the amount of user pages that have

	  not been touched during a given period of time. This information can