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mm/compaction: Disable compact_unevictable_allowed on RT

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Since commit 5bbe3547aa ("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>
This commit is contained in:
Sebastian Andrzej Siewior
2020-04-01 21:10:42 -07:00
committed by Linus Torvalds
parent 964b692daf
commit 6923aa0d8c
3 changed files with 35 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/sysctl.c
+28 -1
View File
@@ -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