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Add TASKQ_DYNAMIC feature

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Setting the TASKQ_DYNAMIC flag will create a taskq with dynamic
semantics.  Initially only a single worker thread will be created
to service tasks dispatched to the queue.  As additional threads
are needed they will be dynamically spawned up to the max number
specified by 'nthreads'.  When the threads are no longer needed,
because the taskq is empty, they will automatically terminate.

Due to the low cost of creating and destroying threads under Linux
by default new threads and spawned and terminated aggressively.
There are two modules options which can be tuned to adjust this
behavior if needed.

* spl_taskq_thread_sequential - The number of sequential tasks,
without interruption, which needed to be handled by a worker
thread before a new worker thread is spawned.  Default 4.

* spl_taskq_thread_dynamic - Provides the ability to completely
disable the use of dynamic taskqs on the system.  This is provided
for the purposes of debugging and troubleshooting.  Default 1
(enabled).

This behavior is fundamentally consistent with the dynamic taskq
implementation found in both illumos and FreeBSD.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #458
This commit is contained in:
Brian Behlendorf
2015-06-08 14:36:27 -07:00
parent 5acb2307b2
commit f7a973d99b
4 changed files with 413 additions and 168 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/sys/taskq.h
+5 -3
View File
@@ -40,6 +40,7 @@
#define TASKQ_DYNAMIC 0x00000004
#define TASKQ_THREADS_CPU_PCT 0x00000008
#define TASKQ_DC_BATCH 0x00000010
#define TASKQ_ACTIVE 0x80000000
/*
* Flags for taskq_dispatch. TQ_SLEEP/TQ_NOSLEEP should be same as
@@ -53,7 +54,6 @@
#define TQ_NOALLOC 0x02000000
#define TQ_NEW 0x04000000
#define TQ_FRONT 0x08000000
#define TQ_ACTIVE 0x80000000
typedef unsigned long taskqid_t;
typedef void (task_func_t)(void *);
@@ -61,11 +61,13 @@ typedef void (task_func_t)(void *);
typedef struct taskq {
spinlock_t tq_lock; /* protects taskq_t */
unsigned long tq_lock_flags; /* interrupt state */
const char *tq_name; /* taskq name */
char *tq_name; /* taskq name */
struct list_head tq_thread_list;/* list of all threads */
struct list_head tq_active_list;/* list of active threads */
int tq_nactive; /* # of active threads */
int tq_nthreads; /* # of total threads */
int tq_nthreads; /* # of existing threads */
int tq_nspawn; /* # of threads being spawned */
int tq_maxthreads; /* # of threads maximum */
int tq_pri; /* priority */
int tq_minalloc; /* min task_t pool size */
int tq_maxalloc; /* max task_t pool size */