Re: [PATCH] sched: select 'idle' cfs_rq per task-group to prevent tg-internal imbalance

From: Peter Zijlstra
Date: Wed Jul 02 2014 - 09:15:23 EST

On Wed, Jul 02, 2014 at 02:49:18PM +0200, Peter Zijlstra wrote:
> Clearly I need to go take out all these things because people don't seem
> to know this and SCHED_DEBUG isn't a big enough hint. Tedious.

Maybe this would be enough clue?

---
include/linux/kernel.h | 1 +
include/linux/sched/sysctl.h | 6 +++++
kernel/panic.c | 2 ++
kernel/sched/core.c | 59 +++++++++++++++++++++++++++++++++++---------
kernel/sched/fair.c | 3 +++
kernel/sched/sched.h | 2 ++
kernel/sysctl.c | 18 +++++++-------
7 files changed, 70 insertions(+), 21 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4c52907a6d8b..e2dd5ca9e6bf 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -470,6 +470,7 @@ extern enum system_states {
#define TAINT_FIRMWARE_WORKAROUND 11
#define TAINT_OOT_MODULE 12
#define TAINT_UNSIGNED_MODULE 13
+#define TAINT_DEBUG 14

extern const char hex_asc[];
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 596a0e007c62..9d8f04bc555d 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -60,6 +60,12 @@ extern unsigned int sysctl_sched_time_avg;
extern unsigned int sysctl_timer_migration;
extern unsigned int sysctl_sched_shares_window;

+int sched_debug_proc_dointvec_minmax(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
+int sched_debug_proc_doulongvec_minmax(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
int sched_proc_update_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length,
loff_t *ppos);
diff --git a/kernel/panic.c b/kernel/panic.c
index 62e16cef9cc2..e407bf59546c 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -224,6 +224,7 @@ static const struct tnt tnts[] = {
{ TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
{ TAINT_OOT_MODULE, 'O', ' ' },
{ TAINT_UNSIGNED_MODULE, 'E', ' ' },
+ { TAINT_DEBUG, 'G', ' ' },
};

/**
@@ -243,6 +244,7 @@ static const struct tnt tnts[] = {
* 'I' - Working around severe firmware bug.
* 'O' - Out-of-tree module has been loaded.
* 'E' - Unsigned module has been loaded.
+ * 'G' - The user fiddled with nonstandard settings.
*
* The string is overwritten by the next call to print_tainted().
*/
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f11515cf070b..851f6bf6abea 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -159,6 +159,36 @@ const_debug unsigned int sysctl_sched_features =
#undef SCHED_FEAT

#ifdef CONFIG_SCHED_DEBUG
+void sched_debug_taint(void)
+{
+ static bool once;
+
+ if (once)
+ return;
+
+ once = true;
+ add_taint(TAINT_DEBUG, true);
+ printk(KERN_WARN "Tained kernel 'G' -- poking at debug settings.\n");
+}
+
+int sched_debug_proc_dointvec_minmax(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ if (write)
+ sched_debug_taint();
+
+ return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+}
+
+int sched_debug_proc_doulongvec_minmax(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ if (write)
+ sched_debug_taint();
+
+ return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+}
+
#define SCHED_FEAT(name, enabled) \
#name ,

@@ -246,6 +276,8 @@ sched_feat_write(struct file *filp, const char __user *ubuf,
char *cmp;
int i;

+ sched_debug_taint();
+
if (cnt > 63)
cnt = 63;

@@ -1855,6 +1887,9 @@ int sysctl_numa_balancing(struct ctl_table *table, int write,
int err;
int state = numabalancing_enabled;

+ if (write)
+ sched_debug_taint();
+
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;

@@ -4956,31 +4991,31 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
return NULL;

set_table_entry(&table[0], "min_interval", &sd->min_interval,
- sizeof(long), 0644, proc_doulongvec_minmax, false);
+ sizeof(long), 0644, sched_debug_proc_doulongvec_minmax, false);
set_table_entry(&table[1], "max_interval", &sd->max_interval,
- sizeof(long), 0644, proc_doulongvec_minmax, false);
+ sizeof(long), 0644, sched_debug_proc_doulongvec_minmax, false);
set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
- sizeof(int), 0644, proc_dointvec_minmax, true);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, true);
set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
- sizeof(int), 0644, proc_dointvec_minmax, true);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, true);
set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
- sizeof(int), 0644, proc_dointvec_minmax, true);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, true);
set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
- sizeof(int), 0644, proc_dointvec_minmax, true);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, true);
set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
- sizeof(int), 0644, proc_dointvec_minmax, true);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, true);
set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
- sizeof(int), 0644, proc_dointvec_minmax, false);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, false);
set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
- sizeof(int), 0644, proc_dointvec_minmax, false);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, false);
set_table_entry(&table[9], "cache_nice_tries",
&sd->cache_nice_tries,
- sizeof(int), 0644, proc_dointvec_minmax, false);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, false);
set_table_entry(&table[10], "flags", &sd->flags,
- sizeof(int), 0644, proc_dointvec_minmax, false);
+ sizeof(int), 0644, sched_debug_proc_dointvec_minmax, false);
set_table_entry(&table[11], "max_newidle_lb_cost",
&sd->max_newidle_lb_cost,
- sizeof(long), 0644, proc_doulongvec_minmax, false);
+ sizeof(long), 0644, sched_debug_proc_doulongvec_minmax, false);
set_table_entry(&table[12], "name", sd->name,
CORENAME_MAX_SIZE, 0444, proc_dostring, false);
/* &table[13] is terminator */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 923fe32db6b3..e09202eb348f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -577,6 +577,9 @@ int sched_proc_update_handler(struct ctl_table *table, int write,
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
int factor = get_update_sysctl_factor();

+ if (write)
+ sched_debug_taint();
+
if (ret || !write)
return ret;

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0191ed563bdd..fa880ca9ee4a 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -874,6 +874,8 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
# define const_debug const
#endif

+extern void sched_debug_taint(void);
+
extern const_debug unsigned int sysctl_sched_features;

#define SCHED_FEAT(name, enabled) \
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7de6555cfea0..f9810984f3ca 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -328,35 +328,35 @@ static struct ctl_table kern_table[] = {
.data = &sysctl_sched_migration_cost,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "sched_nr_migrate",
.data = &sysctl_sched_nr_migrate,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "sched_time_avg_ms",
.data = &sysctl_sched_time_avg,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "sched_shares_window_ns",
.data = &sysctl_sched_shares_window,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "timer_migration",
.data = &sysctl_timer_migration,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
.extra1 = &zero,
.extra2 = &one,
},
@@ -367,28 +367,28 @@ static struct ctl_table kern_table[] = {
.data = &sysctl_numa_balancing_scan_delay,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "numa_balancing_scan_period_min_ms",
.data = &sysctl_numa_balancing_scan_period_min,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "numa_balancing_scan_period_max_ms",
.data = &sysctl_numa_balancing_scan_period_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "numa_balancing_scan_size_mb",
.data = &sysctl_numa_balancing_scan_size,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sched_debug_proc_dointvec_minmax,
},
{
.procname = "numa_balancing",

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