From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-mm@kvack.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH] mm/compaction: Disable compact_unevictable_allowed on RT
Date: Wed, 15 Jan 2020 17:10:35 +0100 [thread overview]
Message-ID: <20200115161035.893221-1-bigeasy@linutronix.de> (raw)
Since commit
5bbe3547aa3ba ("mm: allow compaction of unevictable pages")
it is allowed to examine mlocked pages and compact them by default.
On -RT even minor pagefaults are problematic because it may take a few
100us to resolve them and until then the task is blocked.
Make compact_unevictable_allowed = 0 default and remove it from /proc on
RT.
Link: https://lore.kernel.org/linux-mm/20190710144138.qyn4tuttdq6h7kqx@linutronix.de/
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/sysctl.c | 3 ++-
mm/compaction.c | 4 ++++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 70665934d53e2..d08bd51a0fbc3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1488,6 +1488,7 @@ static struct ctl_table vm_table[] = {
.extra1 = &min_extfrag_threshold,
.extra2 = &max_extfrag_threshold,
},
+#ifndef CONFIG_PREEMPT_RT
{
.procname = "compact_unevictable_allowed",
.data = &sysctl_compact_unevictable_allowed,
@@ -1497,7 +1498,7 @@ static struct ctl_table vm_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
-
+#endif
#endif /* CONFIG_COMPACTION */
{
.procname = "min_free_kbytes",
diff --git a/mm/compaction.c b/mm/compaction.c
index 672d3c78c6abf..b2c804c35ae56 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1590,7 +1590,11 @@ typedef enum {
* Allow userspace to control policy on scanning the unevictable LRU for
* compactable pages.
*/
+#ifdef CONFIG_PREEMPT_RT
+#define sysctl_compact_unevictable_allowed 0
+#else
int sysctl_compact_unevictable_allowed __read_mostly = 1;
+#endif
static inline void
update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
--
2.25.0.rc2
next reply other threads:[~2020-01-15 16:10 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 16:10 Sebastian Andrzej Siewior [this message]
2020-01-15 22:04 ` [PATCH] mm/compaction: Disable compact_unevictable_allowed on RT Vlastimil Babka
2020-01-16 10:22 ` Sebastian Andrzej Siewior
2020-03-02 17:35 ` [PATCH v2] " Sebastian Andrzej Siewior
2020-03-02 21:25 ` Andrew Morton
2020-03-03 17:59 ` Sebastian Andrzej Siewior
2020-03-03 20:20 ` [PATCH 1/2] =?UTF-8?q?mm/compaction:=20Really=20limit=20compact?= =?UTF-8?q?=5Funevictable=5Fallowed=20to=200=E2=80=A61?= Sebastian Andrzej Siewior
2020-03-03 20:22 ` [PATCH 2/2 v3] mm/compaction: Disable compact_unevictable_allowed on RT Sebastian Andrzej Siewior
2020-03-03 23:56 ` Andrew Morton
2020-03-04 8:19 ` Vlastimil Babka
2020-03-04 9:27 ` Sebastian Andrzej Siewior
2020-03-19 16:39 ` [PATCH 2/2 v4] " Sebastian Andrzej Siewior
2020-03-19 16:49 ` Vlastimil Babka
2020-03-19 16:55 ` [PATCH 2/2 v5] " Sebastian Andrzej Siewior
2020-03-04 8:18 ` [PATCH 2/2 v3] " Vlastimil Babka
2020-03-04 9:25 ` Sebastian Andrzej Siewior
2020-03-04 9:11 ` Mel Gorman
2020-03-04 8:12 ` [PATCH 1/2] mm/compaction: Really limit compact_unevictable_allowed to 0…1 Vlastimil Babka
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