[POWERPC] spufs: Implement /proc/spu_loadavg

Provide load average information for spu context.  The format
is identical to /proc/loadavg, which is also where a lot of code
and concepts is borrowed from.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 127 insertions, 8 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/context.c b/arch/powerpc/platforms/cell/spufs/context.c
index 6ff2a75589f3..f623d963fdc7 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -23,10 +23,14 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <asm/atomic.h>
 #include <asm/spu.h>
 #include <asm/spu_csa.h>
 #include "spufs.h"
 
+
+atomic_t nr_spu_contexts = ATOMIC_INIT(0);
+
 struct spu_context *alloc_spu_context(struct spu_gang *gang)
 {
         struct spu_context *ctx;
@@ -55,6 +59,8 @@ struct spu_context *alloc_spu_context(struct spu_gang *gang)
                 spu_gang_add_ctx(gang, ctx);
         ctx->cpus_allowed = current->cpus_allowed;
         spu_set_timeslice(ctx);
+
+        atomic_inc(&nr_spu_contexts);
         goto out;
 out_free:
         kfree(ctx);
@@ -74,6 +80,7 @@ void destroy_spu_context(struct kref *kref)
         if (ctx->gang)
                 spu_gang_remove_ctx(ctx->gang, ctx);
         BUG_ON(!list_empty(&ctx->rq));
+        atomic_dec(&nr_spu_contexts);
         kfree(ctx);
 }
 
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 540067550e88..9fc09306c9ae 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -36,6 +36,9 @@
 #include <linux/mutex.h>
 #include <linux/notifier.h>
 #include <linux/kthread.h>
+#include <linux/pid_namespace.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
@@ -50,8 +53,11 @@ struct spu_prio_array {
         spinlock_t runq_lock;
         struct list_head active_list[MAX_NUMNODES];
         struct mutex active_mutex[MAX_NUMNODES];
+        int nr_active[MAX_NUMNODES];
+        int nr_waiting;
 };
 
+static unsigned long spu_avenrun[3];
 static struct spu_prio_array *spu_prio;
 static struct task_struct *spusched_task;
 static struct timer_list spusched_timer;
@@ -169,14 +175,18 @@ static int node_allowed(struct spu_context *ctx, int node)
  */
 static void spu_add_to_active_list(struct spu *spu)
 {
-        mutex_lock(&spu_prio->active_mutex[spu->node]);
-        list_add_tail(&spu->list, &spu_prio->active_list[spu->node]);
-        mutex_unlock(&spu_prio->active_mutex[spu->node]);
+        int node = spu->node;
+
+        mutex_lock(&spu_prio->active_mutex[node]);
+        spu_prio->nr_active[node]++;
+        list_add_tail(&spu->list, &spu_prio->active_list[node]);
+        mutex_unlock(&spu_prio->active_mutex[node]);
 }
 
 static void __spu_remove_from_active_list(struct spu *spu)
 {
         list_del_init(&spu->list);
+        spu_prio->nr_active[spu->node]--;
 }
 
 /**
@@ -275,6 +285,7 @@ static void __spu_add_to_rq(struct spu_context *ctx)
 {
         int prio = ctx->prio;
 
+        spu_prio->nr_waiting++;
         list_add_tail(&ctx->rq, &spu_prio->runq[prio]);
         set_bit(prio, spu_prio->bitmap);
 }
@@ -283,8 +294,10 @@ static void __spu_del_from_rq(struct spu_context *ctx)
 {
         int prio = ctx->prio;
 
-        if (!list_empty(&ctx->rq))
+        if (!list_empty(&ctx->rq)) {
                 list_del_init(&ctx->rq);
+                spu_prio->nr_waiting--;
+        }
         if (list_empty(&spu_prio->runq[prio]))
                 clear_bit(prio, spu_prio->bitmap);
 }
@@ -567,10 +580,56 @@ static void spusched_tick(struct spu_context *ctx)
         }
 }
 
+/**
+ * count_active_contexts - count nr of active tasks
+ *
+ * Return the number of tasks currently running or waiting to run.
+ *
+ * Note that we don't take runq_lock / active_mutex here.  Reading
+ * a single 32bit value is atomic on powerpc, and we don't care
+ * about memory ordering issues here.
+ */
+static unsigned long count_active_contexts(void)
+{
+        int nr_active = 0, node;
+
+        for (node = 0; node < MAX_NUMNODES; node++)
+                nr_active += spu_prio->nr_active[node];
+        nr_active += spu_prio->nr_waiting;
+
+        return nr_active;
+}
+
+/**
+ * spu_calc_load - given tick count, update the avenrun load estimates.
+ * @tick:       tick count
+ *
+ * No locking against reading these values from userspace, as for
+ * the CPU loadavg code.
+ */
+static void spu_calc_load(unsigned long ticks)
+{
+        unsigned long active_tasks; /* fixed-point */
+        static int count = LOAD_FREQ;
+
+        count -= ticks;
+
+        if (unlikely(count < 0)) {
+                active_tasks = count_active_contexts() * FIXED_1;
+                do {
+                        CALC_LOAD(spu_avenrun[0], EXP_1, active_tasks);
+                        CALC_LOAD(spu_avenrun[1], EXP_5, active_tasks);
+                        CALC_LOAD(spu_avenrun[2], EXP_15, active_tasks);
+                        count += LOAD_FREQ;
+                } while (count < 0);
+        }
+}
+
 static void spusched_wake(unsigned long data)
 {
         mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
         wake_up_process(spusched_task);
+        spu_calc_load(SPUSCHED_TICK);
 }
 
 static int spusched_thread(void *unused)
@@ -598,13 +657,52 @@ static int spusched_thread(void *unused)
         return 0;
 }
 
+#define LOAD_INT(x) ((x) >> FSHIFT)
+#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
+
+static int show_spu_loadavg(struct seq_file *s, void *private)
+{
+        int a, b, c;
+
+        a = spu_avenrun[0] + (FIXED_1/200);
+        b = spu_avenrun[1] + (FIXED_1/200);
+        c = spu_avenrun[2] + (FIXED_1/200);
+
+        /*
+         * Note that last_pid doesn't really make much sense for the
+         * SPU loadavg (it even seems very odd on the CPU side..),
+         * but we include it here to have a 100% compatible interface.
+         */
+        seq_printf(s, "%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
+                LOAD_INT(a), LOAD_FRAC(a),
+                LOAD_INT(b), LOAD_FRAC(b),
+                LOAD_INT(c), LOAD_FRAC(c),
+                count_active_contexts(),
+                atomic_read(&nr_spu_contexts),
+                current->nsproxy->pid_ns->last_pid);
+        return 0;
+}
+
+static int spu_loadavg_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, show_spu_loadavg, NULL);
+}
+
+static const struct file_operations spu_loadavg_fops = {
+        .open           = spu_loadavg_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
 int __init spu_sched_init(void)
 {
-        int i;
+        struct proc_dir_entry *entry;
+        int err = -ENOMEM, i;
 
         spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
         if (!spu_prio)
-                return -ENOMEM;
+                goto out;
 
         for (i = 0; i < MAX_PRIO; i++) {
                 INIT_LIST_HEAD(&spu_prio->runq[i]);
@@ -619,14 +717,25 @@ int __init spu_sched_init(void)
 
         spusched_task = kthread_run(spusched_thread, NULL, "spusched");
         if (IS_ERR(spusched_task)) {
-                kfree(spu_prio);
-                return PTR_ERR(spusched_task);
+                err = PTR_ERR(spusched_task);
+                goto out_free_spu_prio;
         }
 
+        entry = create_proc_entry("spu_loadavg", 0, NULL);
+        if (!entry)
+                goto out_stop_kthread;
+        entry->proc_fops = &spu_loadavg_fops;
+
         pr_debug("spusched: tick: %d, min ticks: %d, default ticks: %d\n",
                         SPUSCHED_TICK, MIN_SPU_TIMESLICE, DEF_SPU_TIMESLICE);
         return 0;
 
+ out_stop_kthread:
+        kthread_stop(spusched_task);
+ out_free_spu_prio:
+        kfree(spu_prio);
+ out:
+        return err;
 }
 
 void __exit spu_sched_exit(void)
@@ -634,6 +743,8 @@ void __exit spu_sched_exit(void)
         struct spu *spu, *tmp;
         int node;
 
+        remove_proc_entry("spu_loadavg", NULL);
+
         kthread_stop(spusched_task);
 
         for (node = 0; node < MAX_NUMNODES; node++) {
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index 8ff16b4b6bd7..7f5d0b2fdea3 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -176,6 +176,7 @@ void spu_gang_add_ctx(struct spu_gang *gang, struct spu_context *ctx);
 int spufs_handle_class1(struct spu_context *ctx);
 
 /* context management */
+extern atomic_t nr_spu_contexts;
 static inline void spu_acquire(struct spu_context *ctx)
 {
         mutex_lock(&ctx->state_mutex);