35d8ba6629
This changes the worker thread pool to maintain a list of idle threads, avoiding a complex search for a good thread to wake up. Threads have two states: idle - we try to reuse the last thread used in hopes of improving the batching ratios busy - each time a new work item is added to a busy task, the task is rotated to the end of the line. Signed-off-by: Chris Mason <chris.mason@oracle.com>
80 lines
2.5 KiB
C
80 lines
2.5 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __BTRFS_ASYNC_THREAD_
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#define __BTRFS_ASYNC_THREAD_
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struct btrfs_worker_thread;
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/*
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* This is similar to a workqueue, but it is meant to spread the operations
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* across all available cpus instead of just the CPU that was used to
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* queue the work. There is also some batching introduced to try and
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* cut down on context switches.
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*
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* By default threads are added on demand up to 2 * the number of cpus.
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* Changing struct btrfs_workers->max_workers is one way to prevent
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* demand creation of kthreads.
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*
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* the basic model of these worker threads is to embed a btrfs_work
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* structure in your own data struct, and use container_of in a
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* work function to get back to your data struct.
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*/
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struct btrfs_work {
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/*
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* only func should be set to the function you want called
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* your work struct is passed as the only arg
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*/
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void (*func)(struct btrfs_work *work);
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/*
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* flags should be set to zero. It is used to make sure the
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* struct is only inserted once into the list.
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*/
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unsigned long flags;
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/* don't touch these */
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struct btrfs_worker_thread *worker;
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struct list_head list;
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};
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struct btrfs_workers {
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/* current number of running workers */
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int num_workers;
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/* max number of workers allowed. changed by btrfs_start_workers */
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int max_workers;
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/* once a worker has this many requests or fewer, it is idle */
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int idle_thresh;
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/* list with all the work threads */
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struct list_head worker_list;
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struct list_head idle_list;
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/* lock for finding the next worker thread to queue on */
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spinlock_t lock;
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};
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int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
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int btrfs_start_workers(struct btrfs_workers *workers, int num_workers);
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int btrfs_stop_workers(struct btrfs_workers *workers);
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void btrfs_init_workers(struct btrfs_workers *workers, int max);
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int btrfs_requeue_work(struct btrfs_work *work);
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#endif
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