[RFC PATCH 20/23] vinyl: use cbus for communication between scheduler and worker threads
Vladimir Davydov
vdavydov.dev at gmail.com
Sun Jul 8 19:48:51 MSK 2018
We need cbus for forwarding deferred DELETE statements generated in a
worker thread during primary index compaction to the tx thread where
they can be inserted into secondary indexes. Since pthread mutex/cond
and cbus are incompatible by their nature, let's rework communication
channel between the tx and worker threads using cbus.
Needed for #2129
---
src/box/vy_scheduler.c | 215 ++++++++++++++++++++++++++++++-------------------
src/box/vy_scheduler.h | 25 +-----
2 files changed, 134 insertions(+), 106 deletions(-)
diff --git a/src/box/vy_scheduler.c b/src/box/vy_scheduler.c
index 4d84f9bc..bd3ad4be 100644
--- a/src/box/vy_scheduler.c
+++ b/src/box/vy_scheduler.c
@@ -46,6 +46,7 @@
#include "errinj.h"
#include "fiber.h"
#include "fiber_cond.h"
+#include "cbus.h"
#include "salad/stailq.h"
#include "say.h"
#include "vy_lsm.h"
@@ -55,14 +56,34 @@
#include "vy_run.h"
#include "vy_write_iterator.h"
#include "trivia/util.h"
-#include "tt_pthread.h"
/* Min and max values for vy_scheduler::timeout. */
#define VY_SCHEDULER_TIMEOUT_MIN 1
#define VY_SCHEDULER_TIMEOUT_MAX 60
-static void *vy_worker_f(void *);
+static int vy_worker_f(va_list);
static int vy_scheduler_f(va_list);
+static void vy_task_execute_f(struct cmsg *);
+static void vy_task_complete_f(struct cmsg *);
+
+static const struct cmsg_hop vy_task_execute_route[] = {
+ { vy_task_execute_f, NULL },
+};
+
+static const struct cmsg_hop vy_task_complete_route[] = {
+ { vy_task_complete_f, NULL },
+};
+
+/** Vinyl worker thread. */
+struct vy_worker {
+ struct cord cord;
+ /** Pipe from tx to the worker thread. */
+ struct cpipe worker_pipe;
+ /** Pipe from the worker thread to tx. */
+ struct cpipe tx_pipe;
+ /** Link in vy_scheduler::idle_workers. */
+ struct stailq_entry in_idle;
+};
struct vy_task;
@@ -89,10 +110,22 @@ struct vy_task_ops {
};
struct vy_task {
+ /**
+ * CBus message used for sending the task to/from
+ * a worker thread.
+ */
+ struct cmsg cmsg;
/** Virtual method table. */
const struct vy_task_ops *ops;
/** Pointer to the scheduler. */
struct vy_scheduler *scheduler;
+ /** Worker thread this task is assigned to. */
+ struct vy_worker *worker;
+ /**
+ * Fiber that is currently executing this task in
+ * a worker thread.
+ */
+ struct fiber *fiber;
/** Return code of ->execute. */
int status;
/** If ->execute fails, the error is stored here. */
@@ -126,8 +159,6 @@ struct vy_task {
*/
double bloom_fpr;
int64_t page_size;
- /** Link in vy_scheduler::pending_tasks. */
- struct stailq_entry in_pending;
/** Link in vy_scheduler::processed_tasks. */
struct stailq_entry in_processed;
};
@@ -241,16 +272,6 @@ vy_compact_heap_less(struct heap_node *a, struct heap_node *b)
#undef HEAP_NAME
static void
-vy_scheduler_async_cb(ev_loop *loop, struct ev_async *watcher, int events)
-{
- (void)loop;
- (void)events;
- struct vy_scheduler *scheduler = container_of(watcher,
- struct vy_scheduler, scheduler_async);
- fiber_cond_signal(&scheduler->scheduler_cond);
-}
-
-static void
vy_scheduler_start_workers(struct vy_scheduler *scheduler)
{
assert(!scheduler->is_worker_pool_running);
@@ -260,17 +281,19 @@ vy_scheduler_start_workers(struct vy_scheduler *scheduler)
scheduler->is_worker_pool_running = true;
scheduler->idle_worker_count = scheduler->worker_pool_size;
scheduler->worker_pool = calloc(scheduler->worker_pool_size,
- sizeof(struct cord));
+ sizeof(*scheduler->worker_pool));
if (scheduler->worker_pool == NULL)
panic("failed to allocate vinyl worker pool");
- ev_async_start(scheduler->scheduler_loop, &scheduler->scheduler_async);
for (int i = 0; i < scheduler->worker_pool_size; i++) {
char name[FIBER_NAME_MAX];
snprintf(name, sizeof(name), "vinyl.writer.%d", i);
- if (cord_start(&scheduler->worker_pool[i], name,
- vy_worker_f, scheduler) != 0)
+ struct vy_worker *worker = &scheduler->worker_pool[i];
+ if (cord_costart(&worker->cord, name, vy_worker_f, worker) != 0)
panic("failed to start vinyl worker thread");
+ cpipe_create(&worker->worker_pipe, name);
+ stailq_add_tail_entry(&scheduler->idle_workers,
+ worker, in_idle);
}
}
@@ -280,16 +303,12 @@ vy_scheduler_stop_workers(struct vy_scheduler *scheduler)
assert(scheduler->is_worker_pool_running);
scheduler->is_worker_pool_running = false;
- /* Wake up worker threads. */
- tt_pthread_mutex_lock(&scheduler->mutex);
- pthread_cond_broadcast(&scheduler->worker_cond);
- tt_pthread_mutex_unlock(&scheduler->mutex);
-
- /* Wait for worker threads to exit. */
- for (int i = 0; i < scheduler->worker_pool_size; i++)
- cord_join(&scheduler->worker_pool[i]);
- ev_async_stop(scheduler->scheduler_loop, &scheduler->scheduler_async);
-
+ for (int i = 0; i < scheduler->worker_pool_size; i++) {
+ struct vy_worker *worker = &scheduler->worker_pool[i];
+ cbus_stop_loop(&worker->worker_pipe);
+ cpipe_destroy(&worker->worker_pipe);
+ cord_join(&worker->cord);
+ }
free(scheduler->worker_pool);
scheduler->worker_pool = NULL;
}
@@ -310,19 +329,14 @@ vy_scheduler_create(struct vy_scheduler *scheduler, int write_threads,
if (scheduler->scheduler_fiber == NULL)
panic("failed to allocate vinyl scheduler fiber");
- scheduler->scheduler_loop = loop();
fiber_cond_create(&scheduler->scheduler_cond);
- ev_async_init(&scheduler->scheduler_async, vy_scheduler_async_cb);
scheduler->worker_pool_size = write_threads;
mempool_create(&scheduler->task_pool, cord_slab_cache(),
sizeof(struct vy_task));
- stailq_create(&scheduler->pending_tasks);
+ stailq_create(&scheduler->idle_workers);
stailq_create(&scheduler->processed_tasks);
- tt_pthread_cond_init(&scheduler->worker_cond, NULL);
- tt_pthread_mutex_init(&scheduler->mutex, NULL);
-
vy_dump_heap_create(&scheduler->dump_heap);
vy_compact_heap_create(&scheduler->compact_heap);
@@ -344,9 +358,6 @@ vy_scheduler_destroy(struct vy_scheduler *scheduler)
if (scheduler->is_worker_pool_running)
vy_scheduler_stop_workers(scheduler);
- tt_pthread_cond_destroy(&scheduler->worker_cond);
- tt_pthread_mutex_destroy(&scheduler->mutex);
-
diag_destroy(&scheduler->diag);
mempool_destroy(&scheduler->task_pool);
fiber_cond_destroy(&scheduler->dump_cond);
@@ -647,6 +658,8 @@ vy_run_discard(struct vy_run *run)
static int
vy_task_write_run(struct vy_task *task)
{
+ enum { YIELD_LOOPS = 32 };
+
struct vy_lsm *lsm = task->lsm;
struct vy_stmt_stream *wi = task->wi;
@@ -668,6 +681,7 @@ vy_task_write_run(struct vy_task *task)
if (wi->iface->start(wi) != 0)
goto fail_abort_writer;
int rc;
+ int loops = 0;
struct tuple *stmt = NULL;
while ((rc = wi->iface->next(wi, &stmt)) == 0 && stmt != NULL) {
inj = errinj(ERRINJ_VY_RUN_WRITE_STMT_TIMEOUT, ERRINJ_DOUBLE);
@@ -678,7 +692,9 @@ vy_task_write_run(struct vy_task *task)
if (rc != 0)
break;
- if (!task->scheduler->is_worker_pool_running) {
+ if (++loops % YIELD_LOOPS == 0)
+ fiber_sleep(0);
+ if (fiber_is_cancelled()) {
diag_set(FiberIsCancelled);
rc = -1;
break;
@@ -1316,6 +1332,62 @@ err_task:
}
/**
+ * Fiber function that actually executes a vinyl task.
+ * After finishing a task, it sends it back to tx.
+ */
+static int
+vy_task_f(va_list va)
+{
+ struct vy_task *task = va_arg(va, struct vy_task *);
+ task->status = task->ops->execute(task);
+ if (task->status != 0) {
+ struct diag *diag = diag_get();
+ assert(!diag_is_empty(diag));
+ diag_move(diag, &task->diag);
+ }
+ cmsg_init(&task->cmsg, vy_task_complete_route);
+ cpipe_push(&task->worker->tx_pipe, &task->cmsg);
+ task->fiber = NULL;
+ return 0;
+}
+
+/**
+ * Callback invoked by a worker thread upon receiving a task.
+ * It schedules a fiber which actually executes the task, so
+ * as not to block the event loop.
+ */
+static void
+vy_task_execute_f(struct cmsg *cmsg)
+{
+ struct vy_task *task = container_of(cmsg, struct vy_task, cmsg);
+ assert(task->fiber == NULL);
+ task->fiber = fiber_new("task", vy_task_f);
+ if (task->fiber == NULL) {
+ task->status = -1;
+ diag_move(diag_get(), &task->diag);
+ cmsg_init(&task->cmsg, vy_task_complete_route);
+ cpipe_push(&task->worker->tx_pipe, &task->cmsg);
+ } else {
+ fiber_start(task->fiber, task);
+ }
+}
+
+/**
+ * Callback invoked by the tx thread upon receiving an executed
+ * task from a worker thread. It adds the task to the processed
+ * task queue and wakes up the scheduler so that it can complete
+ * it.
+ */
+static void
+vy_task_complete_f(struct cmsg *cmsg)
+{
+ struct vy_task *task = container_of(cmsg, struct vy_task, cmsg);
+ stailq_add_tail_entry(&task->scheduler->processed_tasks,
+ task, in_processed);
+ fiber_cond_signal(&task->scheduler->scheduler_cond);
+}
+
+/**
* Create a task for dumping an LSM tree. The new task is returned
* in @ptask. If there's no LSM tree that needs to be dumped @ptask
* is set to NULL.
@@ -1503,13 +1575,10 @@ vy_scheduler_f(va_list va)
struct stailq processed_tasks;
struct vy_task *task, *next;
int tasks_failed = 0, tasks_done = 0;
- bool was_empty;
/* Get the list of processed tasks. */
stailq_create(&processed_tasks);
- tt_pthread_mutex_lock(&scheduler->mutex);
stailq_concat(&processed_tasks, &scheduler->processed_tasks);
- tt_pthread_mutex_unlock(&scheduler->mutex);
/* Complete and delete all processed tasks. */
stailq_foreach_entry_safe(task, next, &processed_tasks,
@@ -1518,6 +1587,8 @@ vy_scheduler_f(va_list va)
tasks_failed++;
else
tasks_done++;
+ stailq_add_entry(&scheduler->idle_workers,
+ task->worker, in_idle);
vy_task_delete(task);
scheduler->idle_worker_count++;
assert(scheduler->idle_worker_count <=
@@ -1553,15 +1624,13 @@ vy_scheduler_f(va_list va)
goto wait;
/* Queue the task and notify workers if necessary. */
- tt_pthread_mutex_lock(&scheduler->mutex);
- was_empty = stailq_empty(&scheduler->pending_tasks);
- stailq_add_tail_entry(&scheduler->pending_tasks,
- task, in_pending);
- if (was_empty)
- tt_pthread_cond_signal(&scheduler->worker_cond);
- tt_pthread_mutex_unlock(&scheduler->mutex);
-
+ assert(!stailq_empty(&scheduler->idle_workers));
+ task->worker = stailq_shift_entry(&scheduler->idle_workers,
+ struct vy_worker, in_idle);
scheduler->idle_worker_count--;
+ cmsg_init(&task->cmsg, vy_task_execute_route);
+ cpipe_push(&task->worker->worker_pipe, &task->cmsg);
+
fiber_reschedule();
continue;
error:
@@ -1597,41 +1666,17 @@ wait:
return 0;
}
-static void *
-vy_worker_f(void *arg)
+static int
+vy_worker_f(va_list ap)
{
- struct vy_scheduler *scheduler = arg;
- struct vy_task *task = NULL;
-
- tt_pthread_mutex_lock(&scheduler->mutex);
- while (scheduler->is_worker_pool_running) {
- /* Wait for a task */
- if (stailq_empty(&scheduler->pending_tasks)) {
- /* Wake scheduler up if there are no more tasks */
- ev_async_send(scheduler->scheduler_loop,
- &scheduler->scheduler_async);
- tt_pthread_cond_wait(&scheduler->worker_cond,
- &scheduler->mutex);
- continue;
- }
- task = stailq_shift_entry(&scheduler->pending_tasks,
- struct vy_task, in_pending);
- tt_pthread_mutex_unlock(&scheduler->mutex);
- assert(task != NULL);
-
- /* Execute task */
- task->status = task->ops->execute(task);
- if (task->status != 0) {
- struct diag *diag = diag_get();
- assert(!diag_is_empty(diag));
- diag_move(diag, &task->diag);
- }
-
- /* Return processed task to scheduler */
- tt_pthread_mutex_lock(&scheduler->mutex);
- stailq_add_tail_entry(&scheduler->processed_tasks,
- task, in_processed);
- }
- tt_pthread_mutex_unlock(&scheduler->mutex);
- return NULL;
+ struct vy_worker *worker = va_arg(ap, struct vy_worker *);
+ struct cbus_endpoint endpoint;
+
+ cpipe_create(&worker->tx_pipe, "tx");
+ cbus_endpoint_create(&endpoint, cord_name(&worker->cord),
+ fiber_schedule_cb, fiber());
+ cbus_loop(&endpoint);
+ cbus_endpoint_destroy(&endpoint, cbus_process);
+ cpipe_destroy(&worker->tx_pipe);
+ return 0;
}
diff --git a/src/box/vy_scheduler.h b/src/box/vy_scheduler.h
index 284f666e..a235aa6f 100644
--- a/src/box/vy_scheduler.h
+++ b/src/box/vy_scheduler.h
@@ -42,16 +42,15 @@
#define HEAP_FORWARD_DECLARATION
#include "salad/heap.h"
#include "salad/stailq.h"
-#include "tt_pthread.h"
#if defined(__cplusplus)
extern "C" {
#endif /* defined(__cplusplus) */
-struct cord;
struct fiber;
struct vy_lsm;
struct vy_run_env;
+struct vy_worker;
struct vy_scheduler;
typedef void
@@ -61,42 +60,26 @@ typedef void
struct vy_scheduler {
/** Scheduler fiber. */
struct fiber *scheduler_fiber;
- /** Scheduler event loop. */
- struct ev_loop *scheduler_loop;
/** Used to wake up the scheduler fiber from TX. */
struct fiber_cond scheduler_cond;
- /** Used to wake up the scheduler from a worker thread. */
- struct ev_async scheduler_async;
/**
* Array of worker threads used for performing
* dump/compaction tasks.
*/
- struct cord *worker_pool;
+ struct vy_worker *worker_pool;
/** Set if the worker threads are running. */
bool is_worker_pool_running;
/** Total number of worker threads. */
int worker_pool_size;
/** Number worker threads that are currently idle. */
int idle_worker_count;
+ /** List of idle workers, linked by vy_worker::in_idle. */
+ struct stailq idle_workers;
/** Memory pool used for allocating vy_task objects. */
struct mempool task_pool;
- /** Queue of pending tasks, linked by vy_task::in_pending. */
- struct stailq pending_tasks;
/** Queue of processed tasks, linked by vy_task::in_processed. */
struct stailq processed_tasks;
/**
- * Signaled to wake up a worker when there is
- * a pending task in the input queue. Also used
- * to stop worker threads on shutdown.
- */
- pthread_cond_t worker_cond;
- /**
- * Mutex protecting input and output queues and
- * the condition variable used to wake up worker
- * threads.
- */
- pthread_mutex_t mutex;
- /**
* Heap of LSM trees, ordered by dump priority,
* linked by vy_lsm::in_dump.
*/
--
2.11.0
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