Add pthread based, parallel block processor implementation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 333 insertions, 0 deletions

diff --git a/lib/comp/block_processor_parallel.c b/lib/comp/block_processor_parallel.c
new file mode 100644
index 0000000..617900f
--- /dev/null
+++ b/lib/comp/block_processor_parallel.c
@@ -0,0 +1,333 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * block_processor.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "block_processor.h"
+#include "util.h"
+
+#include <pthread.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define MAX_BACKLOG_FACTOR (10)
+
+typedef struct {
+	block_processor_t *shared;
+	compressor_t *cmp;
+	pthread_t thread;
+	uint8_t scratch[];
+} compress_worker_t;
+
+struct block_processor_t {
+	pthread_mutex_t mtx;
+	pthread_cond_t queue_cond;
+	pthread_cond_t done_cond;
+
+	/* needs rw access by worker and main thread */
+	block_t *queue;
+	block_t *done;
+	bool terminate;
+	size_t backlog;
+
+	/* used by main thread only */
+	uint32_t enqueue_id;
+	uint32_t dequeue_id;
+
+	unsigned int num_workers;
+	block_cb cb;
+	void *user;
+	int status;
+
+	/* used only by workers */
+	size_t max_block_size;
+
+	compress_worker_t *workers[];
+};
+
+static void store_completed_block(block_processor_t *shared, block_t *blk)
+{
+	block_t *it = shared->done, *prev = NULL;
+
+	while (it != NULL) {
+		if (it->sequence_number >= blk->sequence_number)
+			break;
+		prev = it;
+		it = it->next;
+	}
+
+	if (prev == NULL) {
+		blk->next = shared->done;
+		shared->done = blk;
+	} else {
+		blk->next = prev->next;
+		prev->next = blk;
+	}
+}
+
+static void *worker_proc(void *arg)
+{
+	compress_worker_t *worker = arg;
+	block_processor_t *shared = worker->shared;
+	block_t *blk;
+
+	for (;;) {
+		pthread_mutex_lock(&shared->mtx);
+		while (shared->queue == NULL && !shared->terminate) {
+			pthread_cond_wait(&shared->queue_cond,
+					  &shared->mtx);
+		}
+
+		if (shared->terminate) {
+			pthread_mutex_unlock(&shared->mtx);
+			break;
+		}
+
+		blk = shared->queue;
+		shared->queue = blk->next;
+		blk->next = NULL;
+		pthread_mutex_unlock(&shared->mtx);
+
+		if (process_block(blk, worker->cmp, worker->scratch,
+				  shared->max_block_size)) {
+			blk->flags |= BLK_COMPRESS_ERROR;
+		}
+
+		pthread_mutex_lock(&shared->mtx);
+		store_completed_block(shared, blk);
+		shared->backlog -= 1;
+		pthread_cond_broadcast(&shared->done_cond);
+		pthread_mutex_unlock(&shared->mtx);
+	}
+	return NULL;
+}
+
+block_processor_t *block_processor_create(size_t max_block_size,
+					  compressor_t *cmp,
+					  unsigned int num_workers,
+					  void *user,
+					  block_cb callback)
+{
+	block_processor_t *proc;
+	unsigned int i;
+	size_t size;
+	int ret;
+
+	if (num_workers < 1)
+		num_workers = 1;
+
+	size = sizeof(proc->workers[0]) * num_workers;
+
+	proc = calloc(1, sizeof(*proc) + size);
+	if (proc == NULL) {
+		perror("Creating block processor");
+		return NULL;
+	}
+
+	proc->max_block_size = max_block_size;
+	proc->cb = callback;
+	proc->user = user;
+	proc->num_workers = num_workers;
+
+	if (pthread_mutex_init(&proc->mtx, NULL)) {
+		perror("Creating block processor mutex");
+		goto fail_free;
+	}
+
+	if (pthread_cond_init(&proc->queue_cond, NULL)) {
+		perror("Creating block processor conditional");
+		goto fail_mtx;
+	}
+
+	if (pthread_cond_init(&proc->done_cond, NULL)) {
+		perror("Creating block processor completion conditional");
+		goto fail_cond;
+	}
+
+	size = sizeof(compress_worker_t) + max_block_size;
+
+	for (i = 0; i < num_workers; ++i) {
+		proc->workers[i] = calloc(1, size);
+
+		if (proc->workers[i] == NULL) {
+			perror("Creating block worker data");
+			goto fail_init;
+		}
+
+		proc->workers[i]->shared = proc;
+		proc->workers[i]->cmp = cmp->create_copy(cmp);
+
+		if (proc->workers[i]->cmp == NULL)
+			goto fail_init;
+	}
+
+	for (i = 0; i < num_workers; ++i) {
+		ret = pthread_create(&proc->workers[i]->thread, NULL,
+				     worker_proc, proc->workers[i]);
+
+		if (ret != 0) {
+			perror("Creating block processor thread");
+			goto fail_thread;
+		}
+	}
+
+	return proc;
+fail_thread:
+	pthread_mutex_lock(&proc->mtx);
+	proc->terminate = true;
+	pthread_cond_broadcast(&proc->queue_cond);
+	pthread_mutex_unlock(&proc->mtx);
+
+	for (i = 0; i < num_workers; ++i) {
+		if (proc->workers[i]->thread > 0) {
+			pthread_join(proc->workers[i]->thread, NULL);
+		}
+	}
+fail_init:
+	for (i = 0; i < num_workers; ++i) {
+		if (proc->workers[i] != NULL) {
+			if (proc->workers[i]->cmp != NULL) {
+				proc->workers[i]->cmp->
+					destroy(proc->workers[i]->cmp);
+			}
+
+			free(proc->workers[i]);
+		}
+	}
+	pthread_cond_destroy(&proc->done_cond);
+fail_cond:
+	pthread_cond_destroy(&proc->queue_cond);
+fail_mtx:
+	pthread_mutex_destroy(&proc->mtx);
+fail_free:
+	free(proc);
+	return NULL;
+}
+
+void block_processor_destroy(block_processor_t *proc)
+{
+	unsigned int i;
+	block_t *blk;
+
+	pthread_mutex_lock(&proc->mtx);
+	proc->terminate = true;
+	pthread_cond_broadcast(&proc->queue_cond);
+	pthread_mutex_unlock(&proc->mtx);
+
+	for (i = 0; i < proc->num_workers; ++i) {
+		pthread_join(proc->workers[i]->thread, NULL);
+
+		proc->workers[i]->cmp->destroy(proc->workers[i]->cmp);
+		free(proc->workers[i]);
+	}
+
+	pthread_cond_destroy(&proc->done_cond);
+	pthread_cond_destroy(&proc->queue_cond);
+	pthread_mutex_destroy(&proc->mtx);
+
+	while (proc->queue != NULL) {
+		blk = proc->queue;
+		proc->queue = blk->next;
+		free(blk);
+	}
+
+	while (proc->done != NULL) {
+		blk = proc->done;
+		proc->done = blk->next;
+		free(blk);
+	}
+
+	free(proc);
+}
+
+static int process_completed_blocks(block_processor_t *proc, block_t *queue)
+{
+	block_t *it;
+
+	while (queue != NULL) {
+		it = queue;
+		queue = queue->next;
+
+		if (it->flags & BLK_COMPRESS_ERROR) {
+			proc->status = -1;
+		} else {
+			if (proc->cb(proc->user, it))
+				proc->status = -1;
+		}
+
+		free(it);
+	}
+
+	return proc->status;
+}
+
+int block_processor_enqueue(block_processor_t *proc, block_t *block)
+{
+	block_t *queue = NULL, *it, *prev;
+
+	block->sequence_number = proc->enqueue_id++;
+	block->next = NULL;
+
+	pthread_mutex_lock(&proc->mtx);
+	while (proc->backlog > proc->num_workers * MAX_BACKLOG_FACTOR)
+		pthread_cond_wait(&proc->done_cond, &proc->mtx);
+
+	if (proc->queue == NULL) {
+		proc->queue = block;
+	} else {
+		for (it = proc->queue; it->next != NULL; it = it->next)
+			;
+		it->next = block;
+	}
+
+	proc->backlog += 1;
+	it = proc->done;
+	prev = NULL;
+
+	while (it != NULL && it->sequence_number == proc->dequeue_id) {
+		prev = it;
+		it = it->next;
+		proc->dequeue_id += 1;
+	}
+
+	if (prev != NULL) {
+		queue = proc->done;
+		prev->next = NULL;
+		proc->done = it;
+	}
+
+	pthread_cond_broadcast(&proc->queue_cond);
+	pthread_mutex_unlock(&proc->mtx);
+
+	return process_completed_blocks(proc, queue);
+}
+
+int block_processor_finish(block_processor_t *proc)
+{
+	block_t *queue, *it;
+
+	pthread_mutex_lock(&proc->mtx);
+	while (proc->backlog > 0)
+		pthread_cond_wait(&proc->done_cond, &proc->mtx);
+
+	for (it = proc->done; it != NULL; it = it->next) {
+		if (it->sequence_number != proc->dequeue_id++) {
+			pthread_mutex_unlock(&proc->mtx);
+			goto bug_seqnum;
+		}
+	}
+
+	queue = proc->done;
+	proc->done = NULL;
+	pthread_mutex_unlock(&proc->mtx);
+
+	return process_completed_blocks(proc, queue);
+bug_seqnum:
+	fputs("[BUG][parallel block processor] "
+	      "gap in sequence numbers!\n", stderr);
+	return -1;
+}