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authorDavid Howells <dhowells@redhat.com>2009-04-03 11:42:35 -0400
committerDavid Howells <dhowells@redhat.com>2009-04-03 11:42:35 -0400
commit07fe7cb7c7c179f473fd9c823348fd3eb5dad369 (patch)
tree516c959de929a4c39870629e550b3307601fa73f /include/linux/slow-work.h
parent8fe74cf053de7ad2124a894996f84fa890a81093 (diff)
Create a dynamically sized pool of threads for doing very slow work items
Create a dynamically sized pool of threads for doing very slow work items, such as invoking mkdir() or rmdir() - things that may take a long time and may sleep, holding mutexes/semaphores and hogging a thread, and are thus unsuitable for workqueues. The number of threads is always at least a settable minimum, but more are started when there's more work to do, up to a limit. Because of the nature of the load, it's not suitable for a 1-thread-per-CPU type pool. A system with one CPU may well want several threads. This is used by FS-Cache to do slow caching operations in the background, such as looking up, creating or deleting cache objects. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
Diffstat (limited to 'include/linux/slow-work.h')
-rw-r--r--include/linux/slow-work.h88
1 files changed, 88 insertions, 0 deletions
diff --git a/include/linux/slow-work.h b/include/linux/slow-work.h
new file mode 100644
index 000000000000..4dd754af393e
--- /dev/null
+++ b/include/linux/slow-work.h
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1/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#ifndef _LINUX_SLOW_WORK_H
13#define _LINUX_SLOW_WORK_H
14
15#ifdef CONFIG_SLOW_WORK
16
17struct slow_work;
18
19/*
20 * The operations used to support slow work items
21 */
22struct slow_work_ops {
23 /* get a ref on a work item
24 * - return 0 if successful, -ve if not
25 */
26 int (*get_ref)(struct slow_work *work);
27
28 /* discard a ref to a work item */
29 void (*put_ref)(struct slow_work *work);
30
31 /* execute a work item */
32 void (*execute)(struct slow_work *work);
33};
34
35/*
36 * A slow work item
37 * - A reference is held on the parent object by the thread pool when it is
38 * queued
39 */
40struct slow_work {
41 unsigned long flags;
42#define SLOW_WORK_PENDING 0 /* item pending (further) execution */
43#define SLOW_WORK_EXECUTING 1 /* item currently executing */
44#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
45#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
46 const struct slow_work_ops *ops; /* operations table for this item */
47 struct list_head link; /* link in queue */
48};
49
50/**
51 * slow_work_init - Initialise a slow work item
52 * @work: The work item to initialise
53 * @ops: The operations to use to handle the slow work item
54 *
55 * Initialise a slow work item.
56 */
57static inline void slow_work_init(struct slow_work *work,
58 const struct slow_work_ops *ops)
59{
60 work->flags = 0;
61 work->ops = ops;
62 INIT_LIST_HEAD(&work->link);
63}
64
65/**
66 * slow_work_init - Initialise a very slow work item
67 * @work: The work item to initialise
68 * @ops: The operations to use to handle the slow work item
69 *
70 * Initialise a very slow work item. This item will be restricted such that
71 * only a certain number of the pool threads will be able to execute items of
72 * this type.
73 */
74static inline void vslow_work_init(struct slow_work *work,
75 const struct slow_work_ops *ops)
76{
77 work->flags = 1 << SLOW_WORK_VERY_SLOW;
78 work->ops = ops;
79 INIT_LIST_HEAD(&work->link);
80}
81
82extern int slow_work_enqueue(struct slow_work *work);
83extern int slow_work_register_user(void);
84extern void slow_work_unregister_user(void);
85
86
87#endif /* CONFIG_SLOW_WORK */
88#endif /* _LINUX_SLOW_WORK_H */