syncop: improve scaling and implement more tools

The current scaling of the syncop thread pool is not working properly
and can leave some tasks in the run queue more time than necessary
when the maximum number of threads is not reached.

This patch provides a better scaling condition to react faster to
pending work.

Condition variables and sleep in the context of a synctask have also
been implemented. Their purpose is to replace regular condition
variables and sleeps that block synctask threads and prevent other
tasks to be executed.

The new features have been applied to several places in glusterd.

Change-Id: Ic50b7c73c104f9e41f08101a357d30b95efccfbf
Fixes: #1116
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

3 files changed, 291 insertions, 75 deletions

diff --git a/libglusterfs/src/glusterfs/syncop.h b/libglusterfs/src/glusterfs/syncop.h
index bfdec491ba8..1a801a91444 100644
--- a/libglusterfs/src/glusterfs/syncop.h
+++ b/libglusterfs/src/glusterfs/syncop.h
@@ -16,6 +16,8 @@
 #include <ucontext.h>
 #include "glusterfs/dict.h"   // for dict_t
 #include "glusterfs/stack.h"  // for call_frame_t, STACK_DESTROY, STACK_...
+#include "glusterfs/timer.h"
+
 #define SYNCENV_PROC_MAX 16
 #define SYNCENV_PROC_MIN 2
 #define SYNCPROC_IDLE_TIME 600
@@ -32,6 +34,7 @@
 struct synctask;
 struct syncproc;
 struct syncenv;
+struct synccond;
 
 typedef int (*synctask_cbk_t)(int ret, call_frame_t *frame, void *opaque);
 
@@ -55,9 +58,12 @@ struct synctask {
     call_frame_t *opframe;
     synctask_cbk_t synccbk;
     synctask_fn_t syncfn;
-    synctask_state_t state;
+    struct timespec *delta;
+    gf_timer_t *timer;
+    struct synccond *synccond;
     void *opaque;
     void *stack;
+    synctask_state_t state;
     int woken;
     int slept;
     int ret;
@@ -85,19 +91,21 @@ struct syncproc {
 /* hosts the scheduler thread and framework for executing synctasks */
 struct syncenv {
     struct syncproc proc[SYNCENV_PROC_MAX];
-    int procs;
+
+    pthread_mutex_t mutex;
+    pthread_cond_t cond;
 
     struct list_head runq;
-    int runcount;
     struct list_head waitq;
-    int waitcount;
+
+    int procs;
+    int procs_idle;
+
+    int runcount;
 
     int procmin;
     int procmax;
 
-    pthread_mutex_t mutex;
-    pthread_cond_t cond;
-
     size_t stacksize;
 
     int destroy; /* FLAG to mark syncenv is in destroy mode
@@ -123,6 +131,13 @@ struct synclock {
 };
 typedef struct synclock synclock_t;
 
+struct synccond {
+    pthread_mutex_t pmutex;
+    pthread_cond_t pcond;
+    struct list_head waitq;
+};
+typedef struct synccond synccond_t;
+
 struct syncbarrier {
     gf_boolean_t initialized; /*Set on successful initialization*/
     pthread_mutex_t guard;    /* guard the remaining members, pair @cond */
@@ -219,7 +234,7 @@ struct syncopctx {
 #define __yield(args)                                                          \
     do {                                                                       \
         if (args->task) {                                                      \
-            synctask_yield(args->task);                                        \
+            synctask_yield(args->task, NULL);                                  \
         } else {                                                               \
             pthread_mutex_lock(&args->mutex);                                  \
             {                                                                  \
@@ -310,7 +325,9 @@ synctask_join(struct synctask *task);
 void
 synctask_wake(struct synctask *task);
 void
-synctask_yield(struct synctask *task);
+synctask_yield(struct synctask *task, struct timespec *delta);
+void
+synctask_sleep(int32_t secs);
 void
 synctask_waitfor(struct synctask *task, int count);
 
@@ -408,6 +425,24 @@ synclock_trylock(synclock_t *lock);
 int
 synclock_unlock(synclock_t *lock);
 
+int32_t
+synccond_init(synccond_t *cond);
+
+void
+synccond_destroy(synccond_t *cond);
+
+int
+synccond_wait(synccond_t *cond, synclock_t *lock);
+
+int
+synccond_timedwait(synccond_t *cond, synclock_t *lock, struct timespec *delta);
+
+void
+synccond_signal(synccond_t *cond);
+
+void
+synccond_broadcast(synccond_t *cond);
+
 int
 syncbarrier_init(syncbarrier_t *barrier);
 int
diff --git a/libglusterfs/src/libglusterfs.sym b/libglusterfs/src/libglusterfs.sym
index 47e0872ca59..f5e273e4ca0 100644
--- a/libglusterfs/src/libglusterfs.sym
+++ b/libglusterfs/src/libglusterfs.sym
@@ -937,6 +937,12 @@ syncbarrier_destroy
 syncbarrier_init
 syncbarrier_wait
 syncbarrier_wake
+synccond_init
+synccond_destroy
+synccond_wait
+synccond_timedwait
+synccond_signal
+synccond_broadcast
 syncenv_destroy
 syncenv_new
 synclock_destroy
@@ -1014,6 +1020,7 @@ synctask_new
 synctask_new1
 synctask_set
 synctask_setid
+synctask_sleep
 synctask_wake
 synctask_yield
 sys_access
diff --git a/libglusterfs/src/syncop.c b/libglusterfs/src/syncop.c
index 693970f0f30..71d37b76f25 100644
--- a/libglusterfs/src/syncop.c
+++ b/libglusterfs/src/syncop.c
@@ -154,10 +154,14 @@ out:
     return ret;
 }
 
+void *
+syncenv_processor(void *thdata);
+
 static void
 __run(struct synctask *task)
 {
     struct syncenv *env = NULL;
+    int32_t total, ret, i;
 
     env = task->env;
 
@@ -173,7 +177,6 @@ __run(struct synctask *task)
             env->runcount--;
             break;
         case SYNCTASK_WAIT:
-            env->waitcount--;
             break;
         case SYNCTASK_DONE:
             gf_msg(task->xl->name, GF_LOG_WARNING, 0, LG_MSG_COMPLETED_TASK,
@@ -187,8 +190,27 @@ __run(struct synctask *task)
     }
 
     list_add_tail(&task->all_tasks, &env->runq);
-    env->runcount++;
     task->state = SYNCTASK_RUN;
+
+    env->runcount++;
+
+    total = env->procs + env->runcount - env->procs_idle;
+    if (total > env->procmax) {
+        total = env->procmax;
+    }
+    if (total > env->procs) {
+        for (i = 0; i < env->procmax; i++) {
+            if (env->proc[i].env == NULL) {
+                env->proc[i].env = env;
+                ret = gf_thread_create(&env->proc[i].processor, NULL,
+                                       syncenv_processor, &env->proc[i],
+                                       "sproc%d", i);
+                if ((ret < 0) || (++env->procs >= total)) {
+                    break;
+                }
+            }
+        }
+    }
 }
 
 static void
@@ -210,7 +232,6 @@ __wait(struct synctask *task)
             gf_msg(task->xl->name, GF_LOG_WARNING, 0, LG_MSG_REWAITING_TASK,
                    "re-waiting already waiting "
                    "task");
-            env->waitcount--;
             break;
         case SYNCTASK_DONE:
             gf_msg(task->xl->name, GF_LOG_WARNING, 0, LG_MSG_COMPLETED_TASK,
@@ -223,12 +244,11 @@ __wait(struct synctask *task)
     }
 
     list_add_tail(&task->all_tasks, &env->waitq);
-    env->waitcount++;
     task->state = SYNCTASK_WAIT;
 }
 
 void
-synctask_yield(struct synctask *task)
+synctask_yield(struct synctask *task, struct timespec *delta)
 {
     xlator_t *oldTHIS = THIS;
 
@@ -237,6 +257,8 @@ synctask_yield(struct synctask *task)
     task->proc->sched.uc_flags &= ~_UC_TLSBASE;
 #endif
 
+    task->delta = delta;
+
     if (task->state != SYNCTASK_DONE) {
         task->state = SYNCTASK_SUSPEND;
     }
@@ -249,6 +271,35 @@ synctask_yield(struct synctask *task)
 }
 
 void
+synctask_sleep(int32_t secs)
+{
+    struct timespec delta;
+    struct synctask *task;
+
+    task = synctask_get();
+
+    if (task == NULL) {
+        sleep(secs);
+    } else {
+        delta.tv_sec = secs;
+        delta.tv_nsec = 0;
+
+        synctask_yield(task, &delta);
+    }
+}
+
+static void
+__synctask_wake(struct synctask *task)
+{
+    task->woken = 1;
+
+    if (task->slept)
+        __run(task);
+
+    pthread_cond_broadcast(&task->env->cond);
+}
+
+void
 synctask_wake(struct synctask *task)
 {
     struct syncenv *env = NULL;
@@ -257,13 +308,18 @@ synctask_wake(struct synctask *task)
 
     pthread_mutex_lock(&env->mutex);
     {
-        task->woken = 1;
+        if (task->timer != NULL) {
+            if (gf_timer_call_cancel(task->xl->ctx, task->timer) != 0) {
+                goto unlock;
+            }
 
-        if (task->slept)
-            __run(task);
+            task->timer = NULL;
+            task->synccond = NULL;
+        }
 
-        pthread_cond_broadcast(&env->cond);
+        __synctask_wake(task);
     }
+unlock:
     pthread_mutex_unlock(&env->mutex);
 }
 
@@ -282,7 +338,7 @@ synctask_wrap(void)
 
     task->state = SYNCTASK_DONE;
 
-    synctask_yield(task);
+    synctask_yield(task, NULL);
 }
 
 void
@@ -422,11 +478,6 @@ synctask_create(struct syncenv *env, size_t stacksize, synctask_fn_t fn,
     }
 
     synctask_wake(newtask);
-    /*
-     * Make sure someone's there to execute anything we just put on the
-     * run queue.
-     */
-    syncenv_scale(env);
 
     return newtask;
 err:
@@ -520,8 +571,12 @@ syncenv_task(struct syncproc *proc)
                 goto unlock;
             }
 
+            env->procs_idle++;
+
             sleep_till.tv_sec = time(NULL) + SYNCPROC_IDLE_TIME;
             ret = pthread_cond_timedwait(&env->cond, &env->mutex, &sleep_till);
+
+            env->procs_idle--;
         }
 
         task = list_entry(env->runq.next, struct synctask, all_tasks);
@@ -540,6 +595,34 @@ unlock:
     return task;
 }
 
+static void
+synctask_timer(void *data)
+{
+    struct synctask *task = data;
+    struct synccond *cond;
+
+    cond = task->synccond;
+    if (cond != NULL) {
+        pthread_mutex_lock(&cond->pmutex);
+
+        list_del_init(&task->waitq);
+        task->synccond = NULL;
+
+        pthread_mutex_unlock(&cond->pmutex);
+
+        task->ret = -ETIMEDOUT;
+    }
+
+    pthread_mutex_lock(&task->env->mutex);
+
+    gf_timer_call_cancel(task->xl->ctx, task->timer);
+    task->timer = NULL;
+
+    __synctask_wake(task);
+
+    pthread_mutex_unlock(&task->env->mutex);
+}
+
 void
 synctask_switchto(struct synctask *task)
 {
@@ -572,7 +655,14 @@ synctask_switchto(struct synctask *task)
         } else {
             task->slept = 1;
             __wait(task);
+
+            if (task->delta != NULL) {
+                task->timer = gf_timer_call_after(task->xl->ctx, *task->delta,
+                                                  synctask_timer, task);
+            }
         }
+
+        task->delta = NULL;
     }
     pthread_mutex_unlock(&env->mutex);
 }
@@ -580,65 +670,18 @@ synctask_switchto(struct synctask *task)
 void *
 syncenv_processor(void *thdata)
 {
-    struct syncenv *env = NULL;
     struct syncproc *proc = NULL;
     struct synctask *task = NULL;
 
     proc = thdata;
-    env = proc->env;
-
-    for (;;) {
-        task = syncenv_task(proc);
-        if (!task)
-            break;
 
+    while ((task = syncenv_task(proc)) != NULL) {
         synctask_switchto(task);
-
-        syncenv_scale(env);
     }
 
     return NULL;
 }
 
-void
-syncenv_scale(struct syncenv *env)
-{
-    int diff = 0;
-    int scale = 0;
-    int i = 0;
-    int ret = 0;
-
-    pthread_mutex_lock(&env->mutex);
-    {
-        if (env->procs > env->runcount)
-            goto unlock;
-
-        scale = env->runcount;
-        if (scale > env->procmax)
-            scale = env->procmax;
-        if (scale > env->procs)
-            diff = scale - env->procs;
-        while (diff) {
-            diff--;
-            for (; (i < env->procmax); i++) {
-                if (env->proc[i].processor == 0)
-                    break;
-            }
-
-            env->proc[i].env = env;
-            ret = gf_thread_create(&env->proc[i].processor, NULL,
-                                   syncenv_processor, &env->proc[i],
-                                   "sproc%03hx", env->procs & 0x3ff);
-            if (ret)
-                break;
-            env->procs++;
-            i++;
-        }
-    }
-unlock:
-    pthread_mutex_unlock(&env->mutex);
-}
-
 /* The syncenv threads are cleaned up in this routine.
  */
 void
@@ -715,12 +758,13 @@ syncenv_new(size_t stacksize, int procmin, int procmax)
         newenv->stacksize = stacksize;
     newenv->procmin = procmin;
     newenv->procmax = procmax;
+    newenv->procs_idle = 0;
 
     for (i = 0; i < newenv->procmin; i++) {
         newenv->proc[i].env = newenv;
         ret = gf_thread_create(&newenv->proc[i].processor, NULL,
                                syncenv_processor, &newenv->proc[i], "sproc%d",
-                               newenv->procs);
+                               i);
         if (ret)
             break;
         newenv->procs++;
@@ -810,7 +854,7 @@ __synclock_lock(struct synclock *lock)
             task->woken = 0;
             list_add_tail(&task->waitq, &lock->waitq);
             pthread_mutex_unlock(&lock->guard);
-            synctask_yield(task);
+            synctask_yield(task, NULL);
             /* task is removed from waitq in unlock,
              * under lock->guard.*/
             pthread_mutex_lock(&lock->guard);
@@ -963,6 +1007,136 @@ synclock_unlock(synclock_t *lock)
     return ret;
 }
 
+/* Condition variables */
+
+int32_t
+synccond_init(synccond_t *cond)
+{
+    int32_t ret;
+
+    INIT_LIST_HEAD(&cond->waitq);
+
+    ret = pthread_mutex_init(&cond->pmutex, NULL);
+    if (ret != 0) {
+        return -ret;
+    }
+
+    ret = pthread_cond_init(&cond->pcond, NULL);
+    if (ret != 0) {
+        pthread_mutex_destroy(&cond->pmutex);
+    }
+
+    return -ret;
+}
+
+void
+synccond_destroy(synccond_t *cond)
+{
+    pthread_cond_destroy(&cond->pcond);
+    pthread_mutex_destroy(&cond->pmutex);
+}
+
+int
+synccond_timedwait(synccond_t *cond, synclock_t *lock, struct timespec *delta)
+{
+    struct timespec now;
+    struct synctask *task = NULL;
+    int ret;
+
+    task = synctask_get();
+
+    if (task == NULL) {
+        if (delta != NULL) {
+            timespec_now_realtime(&now);
+            timespec_adjust_delta(&now, *delta);
+        }
+
+        pthread_mutex_lock(&cond->pmutex);
+
+        if (delta == NULL) {
+            ret = -pthread_cond_wait(&cond->pcond, &cond->pmutex);
+        } else {
+            ret = -pthread_cond_timedwait(&cond->pcond, &cond->pmutex, &now);
+        }
+    } else {
+        pthread_mutex_lock(&cond->pmutex);
+
+        list_add_tail(&task->waitq, &cond->waitq);
+        task->synccond = cond;
+
+        ret = synclock_unlock(lock);
+        if (ret == 0) {
+            pthread_mutex_unlock(&cond->pmutex);
+
+            synctask_yield(task, delta);
+
+            ret = synclock_lock(lock);
+            if (ret == 0) {
+                ret = task->ret;
+            }
+            task->ret = 0;
+
+            return ret;
+        }
+
+        list_del_init(&task->waitq);
+    }
+
+    pthread_mutex_unlock(&cond->pmutex);
+
+    return ret;
+}
+
+int
+synccond_wait(synccond_t *cond, synclock_t *lock)
+{
+    return synccond_timedwait(cond, lock, NULL);
+}
+
+void
+synccond_signal(synccond_t *cond)
+{
+    struct synctask *task;
+
+    pthread_mutex_lock(&cond->pmutex);
+
+    if (!list_empty(&cond->waitq)) {
+        task = list_first_entry(&cond->waitq, struct synctask, waitq);
+        list_del_init(&task->waitq);
+
+        pthread_mutex_unlock(&cond->pmutex);
+
+        synctask_wake(task);
+    } else {
+        pthread_cond_signal(&cond->pcond);
+
+        pthread_mutex_unlock(&cond->pmutex);
+    }
+}
+
+void
+synccond_broadcast(synccond_t *cond)
+{
+    struct list_head list;
+    struct synctask *task;
+
+    INIT_LIST_HEAD(&list);
+
+    pthread_mutex_lock(&cond->pmutex);
+
+    list_splice_init(&cond->waitq, &list);
+    pthread_cond_broadcast(&cond->pcond);
+
+    pthread_mutex_unlock(&cond->pmutex);
+
+    while (!list_empty(&list)) {
+        task = list_first_entry(&list, struct synctask, waitq);
+        list_del_init(&task->waitq);
+
+        synctask_wake(task);
+    }
+}
+
 /* Barriers */
 
 int
@@ -1032,7 +1206,7 @@ __syncbarrier_wait(struct syncbarrier *barrier, int waitfor)
             /* called within a synctask */
             list_add_tail(&task->waitq, &barrier->waitq);
             pthread_mutex_unlock(&barrier->guard);
-            synctask_yield(task);
+            synctask_yield(task, NULL);
             pthread_mutex_lock(&barrier->guard);
         } else {
             /* called by a non-synctask */