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authorYorhel <git@yorhel.nl>2013-06-29 12:28:55 +0200
committerYorhel <git@yorhel.nl>2013-06-29 12:37:47 +0200
commitcdeba6e7e187d6295b319337067e8c445a662a3f (patch)
tree659e8aa377b5b5ad3454b036a762718d1660bed5
parent5a631446b8e8bf1a1dac5574aeafe9e0f36452b7 (diff)
Rewrote evtp: + _maxthreads(), - _die(), no more killing idle threads
The previous code would behave badly with respect to killing idle threads, so I removed that feature for now. Instead, I added evtp_maxthreads() to dynamically control the maximum number of threads. The main motivation for this function is to dynamically control the parallelism when hashing files in Globster, but it's also useful for (manually) killing idle threads and for pausing any progress for a while. I also simplified destruction into a single function: evtp_destroy(). This is a bit less confusing, and the old non-blocking evtp_die() wasn't too useful anyway because you don't get a notification on when the threads are actually dead. Similar non-blocking behaviour can be approximated with the current functions by using evtp_maxthreads(tp, 0), waiting for a while, and then calling evtp_destroy(). That, however, doesn't guarantee non-blockyness.
-rw-r--r--README.pod2
-rw-r--r--evtp.c327
-rw-r--r--evtp.h87
-rw-r--r--test/evtp.c12
4 files changed, 212 insertions, 216 deletions
diff --git a/README.pod b/README.pod
index 0cff58c..8c86763 100644
--- a/README.pod
+++ b/README.pod
@@ -16,7 +16,7 @@ An automatically expanding type-safe generic circular buffer.
=item B<evtp> (L<evtp.h|http://g.blicky.net/ylib.git/plain/evtp.h> and L<evtp.c|http://g.blicky.net/ylib.git/plain/evtp.c>)
-A convenient thread pool for libev based on the L<threadpool library|https://github.com/jech/threadpool> by Juliusz Chroboczek.
+A convenient thread pool for libev.
=item B<sqlasync> (L<sqlasync.h|http://g.blicky.net/ylib.git/plain/sqlasync.h> and L<sqlasync.c|http://g.blicky.net/ylib.git/plain/sqlasync.c>)
diff --git a/evtp.c b/evtp.c
index 680e957..eade2d1 100644
--- a/evtp.c
+++ b/evtp.c
@@ -1,24 +1,23 @@
-/*
-Copyright (c) 2009 by Juliusz Chroboczek
-Copyright (c) 2013 by Yoran Heling
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in
-all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-THE SOFTWARE.
+/* Copyright (c) 2013 Yoran Heling
+
+ Permission is hereby granted, free of charge, to any person obtaining
+ a copy of this software and associated documentation files (the
+ "Software"), to deal in the Software without restriction, including
+ without limitation the rights to use, copy, modify, merge, publish,
+ distribute, sublicense, and/or sell copies of the Software, and to
+ permit persons to whom the Software is furnished to do so, subject to
+ the following conditions:
+
+ The above copyright notice and this permission notice shall be included
+ in all copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#if defined(EV_CONFIG_H)
@@ -40,34 +39,53 @@ typedef struct evtp_queue_t {
evtp_work_t *last;
} evtp_queue_t;
+
struct evtp_t {
- int maxthreads, threads, idle;
- evtp_queue_t scheduled, scheduled_back;
- /* Set when we request that all threads die. */
- int dying;
- /* Protects everything. */
pthread_mutex_t lock;
- /* Signalled whenever a new continuation is enqueued or dying is set. */
pthread_cond_t cond;
- /* Signalled whenever a thread dies. */
pthread_cond_t die_cond;
+ evtp_queue_t work, results;
+ int maxthreads, threads, idle, kill;
+ ev_async async;
#if EV_MULTIPLICITY
struct ev_loop *loop;
#endif
- ev_async async;
};
-/* (This was threadpool_run_callbacks()) */
+static evtp_work_t *evtp_dequeue(evtp_queue_t *queue) {
+ evtp_work_t *item;
+
+ if(queue->first == NULL)
+ return NULL;
+
+ item = queue->first;
+ queue->first = item->next;
+ if(item->next == NULL)
+ queue->last = NULL;
+ return item;
+}
+
+
+static void evtp_enqueue(evtp_queue_t *queue, evtp_work_t *item) {
+ item->next = NULL;
+ if(queue->last)
+ queue->last->next = item;
+ else
+ queue->first = item;
+ queue->last = item;
+}
+
+
static void evtp_async(EV_P_ ev_async *async, int revents) {
- evtp_t *threadpool = async->data;
+ evtp_t *tp = async->data;
evtp_work_t *items;
- pthread_mutex_lock(&threadpool->lock);
- items = threadpool->scheduled_back.first;
- threadpool->scheduled_back.first = NULL;
- threadpool->scheduled_back.last = NULL;
- pthread_mutex_unlock(&threadpool->lock);
+ pthread_mutex_lock(&tp->lock);
+ items = tp->results.first;
+ tp->results.first = NULL;
+ tp->results.last = NULL;
+ pthread_mutex_unlock(&tp->lock);
while(items) {
evtp_work_t *first = items;
@@ -82,10 +100,8 @@ static void evtp_async(EV_P_ ev_async *async, int revents) {
evtp_t *evtp_create(EV_P_ int maxthreads) {
evtp_t *tp = calloc(1, sizeof(evtp_t));
- if(tp == NULL)
- return NULL;
-
tp->maxthreads = maxthreads;
+
pthread_mutex_init(&tp->lock, NULL);
pthread_cond_init(&tp->cond, NULL);
pthread_cond_init(&tp->die_cond, NULL);
@@ -102,179 +118,134 @@ evtp_t *evtp_create(EV_P_ int maxthreads) {
}
-int evtp_die(evtp_t *threadpool, int canblock) {
- int done;
+static void *evtp_thread(void *data) {
+ evtp_t *tp = data;
+#if EV_MULTIPLICITY
+ struct ev_loop *loop = tp->loop;
+#endif
- pthread_mutex_lock(&threadpool->lock);
+ pthread_mutex_lock(&tp->lock);
+ while(1) {
+ if(tp->kill > 0) {
+ tp->kill--;
+ if(tp->kill > 0)
+ pthread_cond_signal(&tp->cond);
+ pthread_cond_signal(&tp->die_cond);
+ break;
+ }
- threadpool->dying = 1;
- pthread_cond_broadcast(&threadpool->cond);
+ evtp_work_t *work = evtp_dequeue(&tp->work);
+ if(work) {
+ pthread_mutex_unlock(&tp->lock);
+ work->work_func(work);
+ pthread_mutex_lock(&tp->lock);
+ evtp_enqueue(&tp->results, work);
+ ev_async_send(EV_A_ &tp->async);
+ continue;
+ }
- while(threadpool->threads > 0) {
- if(threadpool->scheduled_back.first || !canblock)
- break;
- pthread_cond_wait(&threadpool->die_cond, &threadpool->lock);
+ tp->idle++;
+ pthread_cond_wait(&tp->cond, &tp->lock);
+ tp->idle--;
}
- done = threadpool->threads == 0;
-
- pthread_mutex_unlock(&threadpool->lock);
- return done;
+ tp->threads--;
+ pthread_mutex_unlock(&tp->lock);
+ return NULL;
}
-int evtp_destroy(evtp_t *threadpool) {
- int dead;
-#if EV_MULTIPLICITY
- struct ev_loop *loop = threadpool->loop;
-#endif
-
- pthread_mutex_lock(&threadpool->lock);
- dead =
- threadpool->threads == 0 &&
- threadpool->scheduled.first == NULL &&
- threadpool->scheduled_back.first == NULL;
- pthread_mutex_unlock(&threadpool->lock);
-
- if(!dead)
- return -1;
-
- pthread_cond_destroy(&threadpool->cond);
- pthread_cond_destroy(&threadpool->die_cond);
- pthread_mutex_destroy(&threadpool->lock);
- ev_ref(EV_A);
- ev_async_stop(EV_A_ &threadpool->async);
- free(threadpool);
+/* Must be called while the lock is held */
+static int evtp_spawn(evtp_t *tp) {
+ if(tp->kill) { /* Why spawn a new thread when we've just attempted to kill one? */
+ tp->kill--;
+ return 1;
+ }
+ pthread_t thread;
+ pthread_attr_t attr;
+ pthread_attr_init(&attr);
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+ int r = pthread_create(&thread, &attr, evtp_thread, tp);
+ if(r) {
+ errno = r;
+ return tp->threads ? 0 : -1;
+ }
+ tp->threads++;
return 1;
}
-static evtp_work_t *evtp_dequeue(evtp_queue_t *queue) {
- evtp_work_t *item;
-
- if(queue->first == NULL)
- return NULL;
+int evtp_maxthreads(evtp_t *tp, int maxthreads) {
+ int r = 1;
+ pthread_mutex_lock(&tp->lock);
+ tp->maxthreads = maxthreads;
- item = queue->first;
- queue->first = item->next;
- if(item->next == NULL)
- queue->last = NULL;
- return item;
-}
+ if(tp->threads > maxthreads) {
+ tp->kill = tp->threads - maxthreads;
+ if(tp->idle)
+ pthread_cond_signal(&tp->cond);
+ }
+ evtp_work_t *work = tp->work.first;
+ while(work && tp->threads-tp->kill < maxthreads && r >= 0) {
+ r = evtp_spawn(tp);
+ work = work->next;
+ }
-static void evtp_enqueue(evtp_queue_t *queue, evtp_work_t *item) {
- item->next = NULL;
- if(queue->last)
- queue->last->next = item;
- else
- queue->first = item;
- queue->last = item;
+ pthread_mutex_unlock(&tp->lock);
+ return r;
}
-static void *thread_main(void *pool) {
- evtp_t *threadpool = pool;
- evtp_work_t *item;
+int evtp_submit(evtp_work_t *work, evtp_t *tp, evtp_func_t work_func, evtp_func_t done_func) {
#if EV_MULTIPLICITY
- struct ev_loop *loop = threadpool->loop;
+ struct ev_loop *loop = tp->loop;
#endif
+ int r = 1;
- pthread_mutex_lock(&threadpool->lock);
-
-again:
- if(threadpool->scheduled.first == NULL) {
- struct timespec ts;
-
- if(threadpool->dying)
- goto die;
-
- /* Beware when benchmarking. Under Linux with NPTL, idle threads
- are slightly counter-productive in some benchmarks, but
- extremely productive in others. */
-
- /* This constant may need to be tweaked. */
- if(threadpool->idle >= 2)
- goto die;
+ work->work_func = work_func;
+ work->done_func = done_func;
- /* Don't bother with POSIX clocks. */
- ts.tv_sec = time(NULL) + 1;
- ts.tv_nsec = 0;
+ pthread_mutex_lock(&tp->lock);
+ if(tp->idle <= tp->kill && tp->threads-tp->kill < tp->maxthreads)
+ r = evtp_spawn(tp);
- threadpool->idle++;
- pthread_cond_timedwait(&threadpool->cond, &threadpool->lock, &ts);
- threadpool->idle--;
- if(threadpool->scheduled.first == NULL)
- goto die;
+ if(r >= 0) {
+ evtp_enqueue(&tp->work, work);
+ ev_ref(EV_A);
+ if(tp->idle)
+ pthread_cond_signal(&tp->cond);
}
- item = evtp_dequeue(&threadpool->scheduled);
- pthread_mutex_unlock(&threadpool->lock);
-
- item->work_func(item);
-
- pthread_mutex_lock(&threadpool->lock);
- evtp_enqueue(&threadpool->scheduled_back, item);
- ev_async_send(EV_A_ &threadpool->async);
-
- goto again;
-
-die:
- threadpool->threads--;
- pthread_cond_broadcast(&threadpool->die_cond);
- pthread_mutex_unlock(&threadpool->lock);
- return NULL;
+ pthread_mutex_unlock(&tp->lock);
+ return r;
}
-/* This is called with the pool locked. */
-static int evtp_new_thread(evtp_t *threadpool) {
- pthread_t thread;
- pthread_attr_t attr;
- int rc;
-
- assert(threadpool->threads < threadpool->maxthreads);
-
- pthread_attr_init(&attr);
- pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
- rc = pthread_create(&thread, &attr, thread_main, (void*)threadpool);
- if(rc) {
- errno = rc;
- return -1;
- }
- threadpool->threads++;
- return 1;
-}
-
-
-int evtp_submit(evtp_work_t *work, evtp_t *threadpool, evtp_func_t work_func, evtp_func_t done_func) {
- int rc = 0;
- int dosignal = 1;
+int evtp_destroy(evtp_t *tp, int force) {
#if EV_MULTIPLICITY
- struct ev_loop *loop = threadpool->loop;
+ struct ev_loop *loop = tp->loop;
#endif
- work->work_func = work_func;
- work->done_func = done_func;
- work->next = NULL;
-
- pthread_mutex_lock(&threadpool->lock);
- evtp_enqueue(&threadpool->scheduled, work);
- if(threadpool->idle == 0) {
- dosignal = 0;
- if(threadpool->threads < threadpool->maxthreads) {
- rc = evtp_new_thread(threadpool);
- if(rc < 0 && threadpool->threads > 0)
- rc = 0; /* we'll recover */
- }
+ pthread_mutex_lock(&tp->lock);
+ if(!force && (tp->work.first || tp->results.first)) {
+ pthread_mutex_unlock(&tp->lock);
+ return -1;
}
- if(dosignal)
- pthread_cond_signal(&threadpool->cond);
- pthread_mutex_unlock(&threadpool->lock);
- ev_ref(EV_A);
+ tp->kill = tp->threads;
+ pthread_cond_signal(&tp->cond);
+ while(tp->threads > 0)
+ pthread_cond_wait(&tp->die_cond, &tp->lock);
+ pthread_mutex_unlock(&tp->lock);
- return rc;
+ pthread_cond_destroy(&tp->cond);
+ pthread_cond_destroy(&tp->die_cond);
+ pthread_mutex_destroy(&tp->lock);
+ ev_ref(EV_A);
+ ev_async_stop(EV_A_ &tp->async);
+ free(tp);
+ return 1;
}
/* vim: set noet sw=4 ts=4: */
diff --git a/evtp.h b/evtp.h
index 84d1ebd..25aa675 100644
--- a/evtp.h
+++ b/evtp.h
@@ -1,36 +1,40 @@
-/*
-Copyright (c) 2009 by Juliusz Chroboczek
-Copyright (c) 2013 by Yoran Heling
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in
-all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-THE SOFTWARE.
+/* Copyright (c) 2013 Yoran Heling
+
+ Permission is hereby granted, free of charge, to any person obtaining
+ a copy of this software and associated documentation files (the
+ "Software"), to deal in the Software without restriction, including
+ without limitation the rights to use, copy, modify, merge, publish,
+ distribute, sublicense, and/or sell copies of the Software, and to
+ permit persons to whom the Software is furnished to do so, subject to
+ the following conditions:
+
+ The above copyright notice and this permission notice shall be included
+ in all copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/* This is a thread pool implementation for convenient use with libev[1]. It
- * mimics the libev and libeio[2] API to some extent. The core thread pool code
- * is based on the threadpool library[3] by Juliusz Chroboczek. If you're
- * looking for a generic thread pool that doesn't rely on libev, use that.
+ * mimics the libev and libeio[2] API to some extent.
+ *
+ * The initial thread pool code was based on the threadpool library[3] by
+ * Juliusz Chroboczek, but the current implementation is quite different.
+ * Still, if you're looking for a generic thread pool that doesn't rely on
+ * libev, that might be a good choice.
*
* 1. http://software.schmorp.de/pkg/libev
* 2. http://software.schmorp.de/pkg/libeio
* 3. https://github.com/jech/threadpool
*
* TODO:
+ * - Automatically kill some idle threads? The application can already use
+ * evtp_maxthreads() to achieve the same effect.
* - Cancellation?
* - Allow done_func = NULL? (Implies auto-free()-work-object-when-done)
*/
@@ -65,6 +69,25 @@ struct evtp_work_t {
evtp_t *evtp_create(EV_P_ int maxthreads);
+/* Dynamically change the maximum number of threads. New threads will be
+ * created when this value is increased and there is enough work to do. If this
+ * value is decreased, some threads will be killed to ensure that the number of
+ * threads will remain below the configured maximum.
+ *
+ * Note that a thread can only be killed when it's not running a work_func(),
+ * so there may be a small delay before the new maxthreads value is honored.
+ * Temporarily setting maxthreads to '0' is a valid way to pause processing of
+ * queued work objects.
+ * Temporarily setting maxthreads to '0' directly followed by resetting it to
+ * its previous value is a valid way to kill all idle threads.
+ *
+ * Returns -1 if we have work queued, but pthread_create() failed and we have
+ * no other threads running (fatal), returns 0 if pthread_create() failed but
+ * we still have a worker thread (recoverable), or 1 if everything went fine.
+ */
+int evtp_maxthreads(evtp_t *evtp, int maxthreads);
+
+
/* Submit work to the thread pool. Returns -1 if pthread_create() failed and we
* have no threads running (fatal), 0 if pthread_create() failed but we still
* have a worker thread (recoverable), or 1 if everything went fine.
@@ -91,14 +114,14 @@ static inline evtp_work_t *evtp_submit_new(evtp_t *evtp, evtp_func_t work_func,
}
-/* Cause a thread pool to die. Returns whenever there is new stuff in the
- callback queue, or immediately if canblock is false. Returns true when
- the thread pool is dead. */
-int evtp_die(evtp_t *threadpool, int canblock);
-
-/* Destroy a thread pool. Does nothing and returns -1 if the pool is not
- dead. */
-int evtp_destroy(evtp_t *threadpool);
+/* Destroy a thread pool. If there is still work scheduled, this function does
+ * nothing and returns -1. If force is non-zero, then the thread pool is
+ * destroyed even if there is still work scheduled. In that case, the work_func
+ * and/or done_func callbacks will NOT be run for those objects.
+ *
+ * This function blocks until all threads have been destroyed and returns 1 on
+ * success. */
+int evtp_destroy(evtp_t *threadpool, int force);
#endif
diff --git a/test/evtp.c b/test/evtp.c
index 0cd2740..1b38b44 100644
--- a/test/evtp.c
+++ b/test/evtp.c
@@ -25,7 +25,7 @@
#endif
#ifdef WORK
-#define BENCH_LOOPS 2000
+#define BENCH_LOOPS 8000
#else
#define BENCH_LOOPS 50000
#endif
@@ -54,9 +54,11 @@ static void done_cb(evtp_work_t *w) {
free(w);
done++;
- if(done == 1)
+ if(done == 1) {
+ evtp_maxthreads(tp, 4);
for(i=1; i<50; i++)
evtp_submit_new(tp, work_cb, done_cb, data+i);
+ }
#ifdef BENCH
if(done == 50) {
@@ -88,14 +90,14 @@ static void work_cb(evtp_work_t *w) {
int main(int argc, char **argv) {
ev_default_loop(0);
- tp = evtp_create(EV_DEFAULT_ 4);
+ tp = evtp_create(EV_DEFAULT_ 0);
evtp_submit_new(tp, work_cb, done_cb, data);
+ evtp_maxthreads(tp, 1);
ev_run(EV_DEFAULT_ 0);
- assert(evtp_die(tp, 1) == 1);
- assert(evtp_destroy(tp) == 1);
+ evtp_destroy(tp, 1);
tp = NULL;
int i;