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.

Link: https://lkml.kernel.org/r/20210716081449.22187-5-sj38.park@gmail.com
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Fernand 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 62dc61db9165ad478fc85952b15caf52adb5a0f5..b34486156926e81a3272f9f66e3eda6e81ace5e5 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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)

diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index aff81ba31bd8bdbe845cb2852aebffdea66c1bbb..fabb2e1e087f49923cfce32bcc063284161214c1 100644 (file)
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -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

diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h
index 1e894d34bdceb2a91318bd1ea7796a17deeddf8b..d8a6aecf99cb9f0fc63bc49126b06fe5936d82e4 100644 (file)
--- a/include/linux/page_idle.h
+++ b/include/linux/page_idle.h
@@ -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 */

diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index f160484afc5ce624e424f33f4b35d04a78858d47..a26dbefdf294b5a11027d69d45a756786981158b 100644 (file)
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -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)

diff --git a/mm/Kconfig b/mm/Kconfig
index 504336de9a1e0c314095abf1510fc710e80d7bbe..d0b85dc1242916c48a1276cce57efa444aaa5b5e 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -739,10 +739,18 @@ config DEFERRED_STRUCT_PAGE_INIT
          lifetime of the system until these kthreads finish the
          initialisation.
 
+config PAGE_IDLE_FLAG
+       bool "Add PG_idle and PG_young flags"
+       help
+         This feature adds PG_idle and PG_young flags in 'struct page'.  PTE
+         Accessed bit writers can set the state of the bit in the flags to let
+         other PTE Accessed bit readers don't disturbed.
+
 config IDLE_PAGE_TRACKING
        bool "Enable idle page tracking"
        depends on SYSFS && MMU && BROKEN
        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

diff --git a/mm/page_ext.c b/mm/page_ext.c
index 293b2685fc489d9767a3736c7e0acf8075ca77a3..dfb91653d359eecb15cc57f5e36d702d3b4b13a9 100644 (file)
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -58,11 +58,21 @@
  * can utilize this callback to initialize the state of it correctly.
  */
 
+#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
+static bool need_page_idle(void)
+{
+       return true;
+}
+struct page_ext_operations page_idle_ops = {
+       .need = need_page_idle,
+};
+#endif
+
 static struct page_ext_operations *page_ext_ops[] = {
 #ifdef CONFIG_PAGE_OWNER
        &page_owner_ops,
 #endif
-#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
+#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
        &page_idle_ops,
 #endif
 };

diff --git a/mm/page_idle.c b/mm/page_idle.c
index 64e5344a992ca9d3bc52838130b3e26dd781f2eb..edead6a8a5f91807d6a8b39c9ce947fedacb5f8f 100644 (file)
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -207,16 +207,6 @@ static const struct attribute_group page_idle_attr_group = {
        .name = "page_idle",
 };
 
-#ifndef CONFIG_64BIT
-static bool need_page_idle(void)
-{
-       return true;
-}
-struct page_ext_operations page_idle_ops = {
-       .need = need_page_idle,
-};
-#endif
-
 static int __init page_idle_init(void)
 {
        int err;