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author | David Howells <dhowells@redhat.com> | 2009-04-03 16:42:35 +0100 |
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committer | David Howells <dhowells@redhat.com> | 2009-04-03 16:42:35 +0100 |
commit | 07fe7cb7c7c179f473fd9c823348fd3eb5dad369 (patch) | |
tree | 516c959de929a4c39870629e550b3307601fa73f /include | |
parent | 8fe74cf053de7ad2124a894996f84fa890a81093 (diff) | |
download | linux-stable-07fe7cb7c7c179f473fd9c823348fd3eb5dad369.tar.gz linux-stable-07fe7cb7c7c179f473fd9c823348fd3eb5dad369.tar.bz2 linux-stable-07fe7cb7c7c179f473fd9c823348fd3eb5dad369.zip |
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')
-rw-r--r-- | include/linux/slow-work.h | 88 |
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 @@ -0,0 +1,88 @@ +/* Worker thread pool for slow items, such as filesystem lookups or mkdirs + * + * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#ifndef _LINUX_SLOW_WORK_H +#define _LINUX_SLOW_WORK_H + +#ifdef CONFIG_SLOW_WORK + +struct slow_work; + +/* + * The operations used to support slow work items + */ +struct slow_work_ops { + /* get a ref on a work item + * - return 0 if successful, -ve if not + */ + int (*get_ref)(struct slow_work *work); + + /* discard a ref to a work item */ + void (*put_ref)(struct slow_work *work); + + /* execute a work item */ + void (*execute)(struct slow_work *work); +}; + +/* + * A slow work item + * - A reference is held on the parent object by the thread pool when it is + * queued + */ +struct slow_work { + unsigned long flags; +#define SLOW_WORK_PENDING 0 /* item pending (further) execution */ +#define SLOW_WORK_EXECUTING 1 /* item currently executing */ +#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */ +#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */ + const struct slow_work_ops *ops; /* operations table for this item */ + struct list_head link; /* link in queue */ +}; + +/** + * slow_work_init - Initialise a slow work item + * @work: The work item to initialise + * @ops: The operations to use to handle the slow work item + * + * Initialise a slow work item. + */ +static inline void slow_work_init(struct slow_work *work, + const struct slow_work_ops *ops) +{ + work->flags = 0; + work->ops = ops; + INIT_LIST_HEAD(&work->link); +} + +/** + * slow_work_init - Initialise a very slow work item + * @work: The work item to initialise + * @ops: The operations to use to handle the slow work item + * + * Initialise a very slow work item. This item will be restricted such that + * only a certain number of the pool threads will be able to execute items of + * this type. + */ +static inline void vslow_work_init(struct slow_work *work, + const struct slow_work_ops *ops) +{ + work->flags = 1 << SLOW_WORK_VERY_SLOW; + work->ops = ops; + INIT_LIST_HEAD(&work->link); +} + +extern int slow_work_enqueue(struct slow_work *work); +extern int slow_work_register_user(void); +extern void slow_work_unregister_user(void); + + +#endif /* CONFIG_SLOW_WORK */ +#endif /* _LINUX_SLOW_WORK_H */ |