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Subject[PATCH 1/3] mm, sysctl: make VM stats configurable
Date
This patch adds a tunable interface that allows VM stats configurable, as
suggested by Dave Hansen and Ying Huang.

When performance becomes a bottleneck and you can tolerate some possible
tool breakage and some decreased counter precision (e.g. numa counter), you
can do:
echo [C|c]oarse > /proc/sys/vm/vmstat_mode

When performance is not a bottleneck and you want all tooling to work, you
can do:
echo [S|s]trict > /proc/sys/vm/vmstat_mode

We recommend automatic detection of virtual memory statistics by system,
this is also system default configuration, you can do:
echo [A|a]uto > /proc/sys/vm/vmstat_mode

The next patch handles numa statistics distinctively based-on different VM
stats mode.

Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Suggested-by: Ying Huang <ying.huang@intel.com>
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
---
include/linux/vmstat.h | 14 ++++++++++
kernel/sysctl.c | 7 +++++
mm/vmstat.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index ade7cb5..c3634c7 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -9,6 +9,20 @@

extern int sysctl_stat_interval;

+/*
+ * vmstat_mode:
+ * 0 = auto mode of vmstat, automatic detection of VM statistics.
+ * 1 = strict mode of vmstat, keep all VM statistics.
+ * 2 = coarse mode of vmstat, ignore unimportant VM statistics.
+ */
+#define VMSTAT_AUTO_MODE 0
+#define VMSTAT_STRICT_MODE 1
+#define VMSTAT_COARSE_MODE 2
+#define VMSTAT_MODE_LEN 16
+extern char sysctl_vmstat_mode[];
+extern int sysctl_vmstat_mode_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+
#ifdef CONFIG_VM_EVENT_COUNTERS
/*
* Light weight per cpu counter implementation.
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6648fbb..f5b813b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1234,6 +1234,13 @@ static struct ctl_table kern_table[] = {

static struct ctl_table vm_table[] = {
{
+ .procname = "vmstat_mode",
+ .data = &sysctl_vmstat_mode,
+ .maxlen = VMSTAT_MODE_LEN,
+ .mode = 0644,
+ .proc_handler = sysctl_vmstat_mode_handler,
+ },
+ {
.procname = "overcommit_memory",
.data = &sysctl_overcommit_memory,
.maxlen = sizeof(sysctl_overcommit_memory),
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4bb13e7..e675ad2 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -32,6 +32,76 @@

#define NUMA_STATS_THRESHOLD (U16_MAX - 2)

+int vmstat_mode = VMSTAT_AUTO_MODE;
+char sysctl_vmstat_mode[VMSTAT_MODE_LEN] = "auto";
+static const char *vmstat_mode_name[3] = {"auto", "strict", "coarse"};
+static DEFINE_MUTEX(vmstat_mode_lock);
+
+
+static int __parse_vmstat_mode(char *s)
+{
+ const char *str = s;
+
+ if (strcmp(str, "auto") == 0 || strcmp(str, "Auto") == 0)
+ vmstat_mode = VMSTAT_AUTO_MODE;
+ else if (strcmp(str, "strict") == 0 || strcmp(str, "Strict") == 0)
+ vmstat_mode = VMSTAT_STRICT_MODE;
+ else if (strcmp(str, "coarse") == 0 || strcmp(str, "Coarse") == 0)
+ vmstat_mode = VMSTAT_COARSE_MODE;
+ else {
+ pr_warn("Ignoring invalid vmstat_mode value: %s\n", s);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+int sysctl_vmstat_mode_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ char old_string[VMSTAT_MODE_LEN];
+ int ret, oldval;
+
+ mutex_lock(&vmstat_mode_lock);
+ if (write)
+ strncpy(old_string, (char *)table->data, VMSTAT_MODE_LEN);
+ ret = proc_dostring(table, write, buffer, length, ppos);
+ if (ret || !write) {
+ mutex_unlock(&vmstat_mode_lock);
+ return ret;
+ }
+
+ oldval = vmstat_mode;
+ if (__parse_vmstat_mode((char *)table->data)) {
+ /*
+ * invalid sysctl_vmstat_mode value, restore saved string
+ */
+ strncpy((char *)table->data, old_string, VMSTAT_MODE_LEN);
+ vmstat_mode = oldval;
+ } else {
+ /*
+ * check whether vmstat mode changes or not
+ */
+ if (vmstat_mode == oldval) {
+ /* no change */
+ mutex_unlock(&vmstat_mode_lock);
+ return 0;
+ } else if (vmstat_mode == VMSTAT_AUTO_MODE)
+ pr_info("vmstat mode changes from %s to auto mode\n",
+ vmstat_mode_name[oldval]);
+ else if (vmstat_mode == VMSTAT_STRICT_MODE)
+ pr_info("vmstat mode changes from %s to strict mode\n",
+ vmstat_mode_name[oldval]);
+ else if (vmstat_mode == VMSTAT_COARSE_MODE)
+ pr_info("vmstat mode changes from %s to coarse mode\n",
+ vmstat_mode_name[oldval]);
+ else
+ pr_warn("invalid vmstat_mode:%d\n", vmstat_mode);
+ }
+
+ mutex_unlock(&vmstat_mode_lock);
+ return 0;
+}
+
#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
EXPORT_PER_CPU_SYMBOL(vm_event_states);
--
2.7.4
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