I've not used the slices module nor studied it deeply. So here are some random
comments for your consideration.
* Who would be responsible for *first* initializing the global pool?
* Whoever calls it first "wins" by being able to decide the number of threads.
Maybe the number of threads should not be a parameter to
mlt_slices_init_global_pool(). It could be an environment variable, instead.
* Should there also be a mlt_slices_close_global_pool() so that the library can
be shut down cleanly? Alternately, you could register the pool with
mlt_factory_register_for_clean_up() in mlt_slices_init_global_pool(). For that
matter, the global pool could be created by mlt_factory_init().
* I wonder if the global pool should be initialized and closed by the
application. Or maybe as part of some other initialization like
mlt_factory_init()
* Theoretically speaking, MLT could do well with only two global thread pools:
one for high priority tasks and one for normal priority tasks. Maybe there
should only be two thread pools, they could both be global and services would
be discouraged from creating additional pools. Additionally, in this
hypothetical scenario, there would only be two thread counts to worry about:
the number of global high priority threads and the number of global normal
priority threads.
Those are my random ideas.
Cheers,
~Brian
From: Dan Dennedy <[email protected]>
To: Maksym Veremeyenko <[email protected]>; mlt-devel
<[email protected]>
Sent: Saturday, January 28, 2017 3:19 PM
Subject: [Mlt-devel] RFC mlt_slices global shared pool
It seems to me that outside of the special high-priority, low-latency producer
and consumers, most services should be using one global shared pool to prevent
too many pools and threads created. Here is a code change I am playing with to
add function mlt_slices_init_global_pool(int threads), which runs at normal
priority. What do you think?
--- src/framework/mlt.vers+++ src/framework/mlt.vers@@ -493,4 +493,5 @@
MLT_6.6.0 { global: mlt_slices_count; mlt_slices_init_pool;+
mlt_slices_init_global_pool; } MLT_6.4.0;--- src/framework/mlt_slices.c+++
src/framework/mlt_slices.c@@ -27,6 +27,7 @@ #include <stdlib.h> #include
<unistd.h> #include <pthread.h>+#include <sched.h> #ifdef _WIN32 #ifdef
_WIN32_WINNT #undef _WIN32_WINNT@@ -129,9 +130,9 @@ static void*
mlt_slices_worker( void* p ) /** Initialize a sliced threading context * *
\public \memberof mlt_slices_s- * \param threads number of threads to use for
job list- * \param policy scheduling policy of processing threads- * \param
priority priority value that can be used with the scheduling algorithm+ *
\param threads number of threads to use for job list, 0 for #cpus+ * \param
policy scheduling policy of processing threads, -1 for normal+ * \param
priority priority value that can be used with the scheduling algorithm, -1 for
maximum * \return the context pointer */ @@ -184,6 +185,10 @@ mlt_slices
mlt_slices_init( int threads, int policy, int priority ) pthread_cond_init (
&ctx->cond_var_job, NULL ); pthread_cond_init ( &ctx->cond_var_ready,
NULL ); pthread_attr_init( &tattr );+ if ( policy < 0 )+ policy
= SCHED_OTHER;+ if ( priority < 0 )+ priority =
sched_get_priority_max( policy ); pthread_attr_setschedpolicy( &tattr, policy
); param.sched_priority = priority; pthread_attr_setschedparam( &tattr,
¶m );@@ -309,9 +314,9 @@ void mlt_slices_run( mlt_slices ctx, int jobs,
mlt_slices_proc proc, void* cooki /** Initialize a sliced threading context
pool * * \public \memberof mlt_slices_s- * \param threads number of threads
to use for job list- * \param policy scheduling policy of processing threads- *
\param priority priority value that can be used with the scheduling algorithm+
* \param threads number of threads to use for job list, 0 for #cpus+ * \param
policy scheduling policy of processing threads, -1 for normal+ * \param
priority priority value that can be used with the scheduling algorithm, -1 for
maximum * \param name name of pool of threads * \return the context pointer
*/@@ -355,6 +360,18 @@ mlt_slices mlt_slices_init_pool( int threads, int
policy, int priority, const ch return ctx; } +/** Initialize the global
sliced thread pool.+ *+ * \public \memberof mlt_slices_s+ * \param threads
number of threads to use for job list, 0 for #cpus+ * \return the context
pointer+ */++mlt_slices mlt_slices_init_global_pool(int threads)+{+ return
mlt_slices_init_pool( threads, MLT_SLICES_SCHED_NORMAL,
MLT_SLICES_SCHED_NORMAL, "_mlt_slices_global" );+}+ /** Get the number of
slices. * * \public \memberof mlt_slices_s--- src/framework/mlt_slices.h+++
src/framework/mlt_slices.h@@ -23,6 +23,8 @@ #ifndef MLT_SLICES_H #define
MLT_SLICES_H +#define MLT_SLICES_SCHED_NORMAL (-1)+ struct mlt_slices_s;
typedef struct mlt_slices_s *mlt_slices; /**< pointer to
Sliced processing context object */ @@ -38,4 +40,6 @@ extern int
mlt_slices_count( mlt_slices ctx ); extern mlt_slices mlt_slices_init_pool(
int threads, int policy, int priority, const char* name ); +extern mlt_slices
mlt_slices_init_global_pool( int threads );+ #endif
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