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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2020-04-01 21:10:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:31 -0700
commit6923aa0d8c629a7853822626877dcb11f4f1d354 (patch)
tree6057c6d23a9dc137a70aef7358bb6c26222306f1 /kernel/sysctl.c
parent964b692daf3018ae4b45285c3bcbb2d897cb4b40 (diff)
mm/compaction: Disable compact_unevictable_allowed on RT
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 issue a warning on RT if it is changed. [bigeasy@linutronix.de: v5] Link: https://lore.kernel.org/linux-mm/20190710144138.qyn4tuttdq6h7kqx@linutronix.de/ Link: http://lkml.kernel.org/r/20200319165536.ovi75tsr2seared4@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Iurii Zaikin <yzaikin@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Link: https://lore.kernel.org/linux-mm/20190710144138.qyn4tuttdq6h7kqx@linutronix.de/ Link: http://lkml.kernel.org/r/20200303202225.nhqc3v5gwlb7x6et@linutronix.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
-rw-r--r--kernel/sysctl.c29
1 files changed, 28 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cb650bb9da68..8a176d8727a3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -212,6 +212,11 @@ static int proc_do_cad_pid(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
static int proc_taint(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
+#ifdef CONFIG_COMPACTION
+static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table,
+ int write, void __user *buffer,
+ size_t *lenp, loff_t *ppos);
+#endif
#endif
#ifdef CONFIG_PRINTK
@@ -1467,7 +1472,7 @@ static struct ctl_table vm_table[] = {
.data = &sysctl_compact_unevictable_allowed,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax_warn_RT_change,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
@@ -2555,6 +2560,28 @@ int proc_dointvec(struct ctl_table *table, int write,
return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL);
}
+#ifdef CONFIG_COMPACTION
+static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table,
+ int write, void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ int ret, old;
+
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT) || !write)
+ return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+ old = *(int *)table->data;
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret)
+ return ret;
+ if (old != *(int *)table->data)
+ pr_warn_once("sysctl attribute %s changed by %s[%d]\n",
+ table->procname, current->comm,
+ task_pid_nr(current));
+ return ret;
+}
+#endif
+
/**
* proc_douintvec - read a vector of unsigned integers
* @table: the sysctl table