3 files changed, 203 insertions, 2 deletions

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 8b21786490ee..736d73801cb6 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -26,6 +26,15 @@ void cpuset_update_current_mems_allowed(void);
 int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl);
 extern int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask);
 extern int cpuset_excl_nodes_overlap(const struct task_struct *p);
+
+#define cpuset_memory_pressure_bump()                           \
+        do {                                                    \
+                if (cpuset_memory_pressure_enabled)             \
+                        __cpuset_memory_pressure_bump();        \
+        } while (0)
+extern int cpuset_memory_pressure_enabled;
+extern void __cpuset_memory_pressure_bump(void);
+
 extern struct file_operations proc_cpuset_operations;
 extern char *cpuset_task_status_allowed(struct task_struct *task, char *buffer);
 
@@ -60,6 +69,8 @@ static inline int cpuset_excl_nodes_overlap(const struct task_struct *p)
         return 1;
 }
 
+static inline void cpuset_memory_pressure_bump(void) {}
+
 static inline char *cpuset_task_status_allowed(struct task_struct *task,
                                                         char *buffer)
 {
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 6503c6da4c4f..5a06fef669f8 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -56,6 +56,15 @@
 
 #define CPUSET_SUPER_MAGIC              0x27e0eb
 
+/* See "Frequency meter" comments, below. */
+
+struct fmeter {
+        int cnt;                /* unprocessed events count */
+        int val;                /* most recent output value */
+        time_t time;            /* clock (secs) when val computed */
+        spinlock_t lock;        /* guards read or write of above */
+};
+
 struct cpuset {
         unsigned long flags;            /* "unsigned long" so bitops work */
         cpumask_t cpus_allowed;         /* CPUs allowed to tasks in cpuset */
@@ -80,7 +89,9 @@ struct cpuset {
          * Copy of global cpuset_mems_generation as of the most
          * recent time this cpuset changed its mems_allowed.
          */
-         int mems_generation;
+        int mems_generation;
+
+        struct fmeter fmeter;           /* memory_pressure filter */
 };
 
 /* bits in struct cpuset flags field */
@@ -149,7 +160,7 @@ static struct cpuset top_cpuset = {
 };
 
 static struct vfsmount *cpuset_mount;
-static struct super_block *cpuset_sb = NULL;
+static struct super_block *cpuset_sb;
 
 /*
  * We have two global cpuset semaphores below.  They can nest.
@@ -807,6 +818,19 @@ static int update_nodemask(struct cpuset *cs, char *buf)
 }
 
 /*
+ * Call with manage_sem held.
+ */
+
+static int update_memory_pressure_enabled(struct cpuset *cs, char *buf)
+{
+        if (simple_strtoul(buf, NULL, 10) != 0)
+                cpuset_memory_pressure_enabled = 1;
+        else
+                cpuset_memory_pressure_enabled = 0;
+        return 0;
+}
+
+/*
  * update_flag - read a 0 or a 1 in a file and update associated flag
  * bit: the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE,
  *                              CS_NOTIFY_ON_RELEASE, CS_MEMORY_MIGRATE)
@@ -848,6 +872,104 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
 }
 
 /*
+ * Frequency meter - How fast is some event occuring?
+ *
+ * These routines manage a digitally filtered, constant time based,
+ * event frequency meter.  There are four routines:
+ *   fmeter_init() - initialize a frequency meter.
+ *   fmeter_markevent() - called each time the event happens.
+ *   fmeter_getrate() - returns the recent rate of such events.
+ *   fmeter_update() - internal routine used to update fmeter.
+ *
+ * A common data structure is passed to each of these routines,
+ * which is used to keep track of the state required to manage the
+ * frequency meter and its digital filter.
+ *
+ * The filter works on the number of events marked per unit time.
+ * The filter is single-pole low-pass recursive (IIR).  The time unit
+ * is 1 second.  Arithmetic is done using 32-bit integers scaled to
+ * simulate 3 decimal digits of precision (multiplied by 1000).
+ *
+ * With an FM_COEF of 933, and a time base of 1 second, the filter
+ * has a half-life of 10 seconds, meaning that if the events quit
+ * happening, then the rate returned from the fmeter_getrate()
+ * will be cut in half each 10 seconds, until it converges to zero.
+ *
+ * It is not worth doing a real infinitely recursive filter.  If more
+ * than FM_MAXTICKS ticks have elapsed since the last filter event,
+ * just compute FM_MAXTICKS ticks worth, by which point the level
+ * will be stable.
+ *
+ * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
+ * arithmetic overflow in the fmeter_update() routine.
+ *
+ * Given the simple 32 bit integer arithmetic used, this meter works
+ * best for reporting rates between one per millisecond (msec) and
+ * one per 32 (approx) seconds.  At constant rates faster than one
+ * per msec it maxes out at values just under 1,000,000.  At constant
+ * rates between one per msec, and one per second it will stabilize
+ * to a value N*1000, where N is the rate of events per second.
+ * At constant rates between one per second and one per 32 seconds,
+ * it will be choppy, moving up on the seconds that have an event,
+ * and then decaying until the next event.  At rates slower than
+ * about one in 32 seconds, it decays all the way back to zero between
+ * each event.
+ */
+
+#define FM_COEF 933             /* coefficient for half-life of 10 secs */
+#define FM_MAXTICKS ((time_t)99) /* useless computing more ticks than this */
+#define FM_MAXCNT 1000000       /* limit cnt to avoid overflow */
+#define FM_SCALE 1000           /* faux fixed point scale */
+
+/* Initialize a frequency meter */
+static void fmeter_init(struct fmeter *fmp)
+{
+        fmp->cnt = 0;
+        fmp->val = 0;
+        fmp->time = 0;
+        spin_lock_init(&fmp->lock);
+}
+
+/* Internal meter update - process cnt events and update value */
+static void fmeter_update(struct fmeter *fmp)
+{
+        time_t now = get_seconds();
+        time_t ticks = now - fmp->time;
+
+        if (ticks == 0)
+                return;
+
+        ticks = min(FM_MAXTICKS, ticks);
+        while (ticks-- > 0)
+                fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
+        fmp->time = now;
+
+        fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
+        fmp->cnt = 0;
+}
+
+/* Process any previous ticks, then bump cnt by one (times scale). */
+static void fmeter_markevent(struct fmeter *fmp)
+{
+        spin_lock(&fmp->lock);
+        fmeter_update(fmp);
+        fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
+        spin_unlock(&fmp->lock);
+}
+
+/* Process any previous ticks, then return current value. */
+static int fmeter_getrate(struct fmeter *fmp)
+{
+        int val;
+
+        spin_lock(&fmp->lock);
+        fmeter_update(fmp);
+        val = fmp->val;
+        spin_unlock(&fmp->lock);
+        return val;
+}
+
+/*
  * Attack task specified by pid in 'pidbuf' to cpuset 'cs', possibly
  * writing the path of the old cpuset in 'ppathbuf' if it needs to be
  * notified on release.
@@ -931,6 +1053,8 @@ typedef enum {
         FILE_CPU_EXCLUSIVE,
         FILE_MEM_EXCLUSIVE,
         FILE_NOTIFY_ON_RELEASE,
+        FILE_MEMORY_PRESSURE_ENABLED,
+        FILE_MEMORY_PRESSURE,
         FILE_TASKLIST,
 } cpuset_filetype_t;
 
@@ -984,6 +1108,12 @@ static ssize_t cpuset_common_file_write(struct file *file, const char __user *us
         case FILE_MEMORY_MIGRATE:
                 retval = update_flag(CS_MEMORY_MIGRATE, cs, buffer);
                 break;
+        case FILE_MEMORY_PRESSURE_ENABLED:
+                retval = update_memory_pressure_enabled(cs, buffer);
+                break;
+        case FILE_MEMORY_PRESSURE:
+                retval = -EACCES;
+                break;
         case FILE_TASKLIST:
                 retval = attach_task(cs, buffer, &pathbuf);
                 break;
@@ -1087,6 +1217,12 @@ static ssize_t cpuset_common_file_read(struct file *file, char __user *buf,
         case FILE_MEMORY_MIGRATE:
                 *s++ = is_memory_migrate(cs) ? '1' : '0';
                 break;
+        case FILE_MEMORY_PRESSURE_ENABLED:
+                *s++ = cpuset_memory_pressure_enabled ? '1' : '0';
+                break;
+        case FILE_MEMORY_PRESSURE:
+                s += sprintf(s, "%d", fmeter_getrate(&cs->fmeter));
+                break;
         default:
                 retval = -EINVAL;
                 goto out;
@@ -1440,6 +1576,16 @@ static struct cftype cft_memory_migrate = {
         .private = FILE_MEMORY_MIGRATE,
 };
 
+static struct cftype cft_memory_pressure_enabled = {
+        .name = "memory_pressure_enabled",
+        .private = FILE_MEMORY_PRESSURE_ENABLED,
+};
+
+static struct cftype cft_memory_pressure = {
+        .name = "memory_pressure",
+        .private = FILE_MEMORY_PRESSURE,
+};
+
 static int cpuset_populate_dir(struct dentry *cs_dentry)
 {
         int err;
@@ -1456,6 +1602,8 @@ static int cpuset_populate_dir(struct dentry *cs_dentry)
                 return err;
         if ((err = cpuset_add_file(cs_dentry, &cft_memory_migrate)) < 0)
                 return err;
+        if ((err = cpuset_add_file(cs_dentry, &cft_memory_pressure)) < 0)
+                return err;
         if ((err = cpuset_add_file(cs_dentry, &cft_tasks)) < 0)
                 return err;
         return 0;
@@ -1491,6 +1639,7 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode)
         INIT_LIST_HEAD(&cs->children);
         atomic_inc(&cpuset_mems_generation);
         cs->mems_generation = atomic_read(&cpuset_mems_generation);
+        fmeter_init(&cs->fmeter);
 
         cs->parent = parent;
 
@@ -1580,6 +1729,7 @@ int __init cpuset_init(void)
         top_cpuset.cpus_allowed = CPU_MASK_ALL;
         top_cpuset.mems_allowed = NODE_MASK_ALL;
 
+        fmeter_init(&top_cpuset.fmeter);
         atomic_inc(&cpuset_mems_generation);
         top_cpuset.mems_generation = atomic_read(&cpuset_mems_generation);
 
@@ -1601,6 +1751,9 @@ int __init cpuset_init(void)
         top_cpuset.dentry = root;
         root->d_inode->i_op = &cpuset_dir_inode_operations;
         err = cpuset_populate_dir(root);
+        /* memory_pressure_enabled is in root cpuset only */
+        if (err == 0)
+                err = cpuset_add_file(root, &cft_memory_pressure_enabled);
 out:
         return err;
 }
@@ -1891,6 +2044,42 @@ done:
 }
 
 /*
+ * Collection of memory_pressure is suppressed unless
+ * this flag is enabled by writing "1" to the special
+ * cpuset file 'memory_pressure_enabled' in the root cpuset.
+ */
+
+int cpuset_memory_pressure_enabled;
+
+/**
+ * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
+ *
+ * Keep a running average of the rate of synchronous (direct)
+ * page reclaim efforts initiated by tasks in each cpuset.
+ *
+ * This represents the rate at which some task in the cpuset
+ * ran low on memory on all nodes it was allowed to use, and
+ * had to enter the kernels page reclaim code in an effort to
+ * create more free memory by tossing clean pages or swapping
+ * or writing dirty pages.
+ *
+ * Display to user space in the per-cpuset read-only file
+ * "memory_pressure".  Value displayed is an integer
+ * representing the recent rate of entry into the synchronous
+ * (direct) page reclaim by any task attached to the cpuset.
+ **/
+
+void __cpuset_memory_pressure_bump(void)
+{
+        struct cpuset *cs;
+
+        task_lock(current);
+        cs = current->cpuset;
+        fmeter_markevent(&cs->fmeter);
+        task_unlock(current);
+}
+
+/*
  * proc_cpuset_show()
  *  - Print tasks cpuset path into seq_file.
  *  - Used for /proc/<pid>/cpuset.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ad3d0202cdef..e0e84924171b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -976,6 +976,7 @@ rebalance:
         cond_resched();
 
         /* We now go into synchronous reclaim */
+        cpuset_memory_pressure_bump();
         p->flags |= PF_MEMALLOC;
         reclaim_state.reclaimed_slab = 0;
         p->reclaim_state = &reclaim_state;