[v3,3/3] mm, migrc: Add a sysctl knob to enable/disable MIGRC mechanism
Commit Message
Add a sysctl knob, '/proc/sys/vm/migrc_enable' to switch on/off migrc.
Signed-off-by: Byungchul Park <byungchul@sk.com>
---
mm/migrate.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 43 insertions(+), 1 deletion(-)
Comments
> On Oct 30, 2023, at 9:25 AM, Byungchul Park <byungchul@sk.com> wrote:
>
> Add a sysctl knob, '/proc/sys/vm/migrc_enable' to switch on/off migrc.
Please explain how users are expected to use this knob.
I suspect that the knob and the config option are not useful. You probably
used them for your evaluation or as a “chicken-bit”, but they are not
useful anymore.
On Mon, Oct 30, 2023 at 08:51:35AM +0000, Nadav Amit wrote:
>
> > On Oct 30, 2023, at 9:25 AM, Byungchul Park <byungchul@sk.com> wrote:
> >
> > Add a sysctl knob, '/proc/sys/vm/migrc_enable' to switch on/off migrc.
>
> Please explain how users are expected to use this knob.
>
> I suspect that the knob and the config option are not useful. You probably
> used them for your evaluation or as a “chicken-bit”, but they are not
> useful anymore.
Okay. We can add the sysctl knob when we need it. Will remove it for now.
However, I'm not sure if it'd be okay without CONFIG_MIGRC. I'd like to
see more opinion on it before going with it.
Byungchul
@@ -58,6 +58,48 @@
#include "internal.h"
#ifdef CONFIG_MIGRC
+static int sysctl_migrc_enable = 1;
+#ifdef CONFIG_SYSCTL
+static int sysctl_migrc_enable_handler(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table t;
+ int err;
+ int enabled = sysctl_migrc_enable;
+
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ t = *table;
+ t.data = &enabled;
+ err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+ if (err < 0)
+ return err;
+ if (write)
+ sysctl_migrc_enable = enabled;
+ return err;
+}
+
+static struct ctl_table migrc_sysctls[] = {
+ {
+ .procname = "migrc_enable",
+ .data = NULL, /* filled in by handler */
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = sysctl_migrc_enable_handler,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+ {}
+};
+
+static int __init migrc_sysctl_init(void)
+{
+ register_sysctl_init("vm", migrc_sysctls);
+ return 0;
+}
+late_initcall(migrc_sysctl_init);
+#endif
atomic_t migrc_gen;
@@ -242,7 +284,7 @@ static inline bool migrc_stopped_pending(void)
static bool can_migrc_system(void)
{
- return !migrc_stopped_pending();
+ return sysctl_migrc_enable && !migrc_stopped_pending();
}
#else
static inline void migrc_mark_folios(struct folio *fsrc, struct folio *fdst) {}