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df5d2e9089
This patch allows the administrator to reduce the rate at which kcopyd issues I/O. Each module that uses kcopyd acquires a throttle parameter that can be set in /sys/module/*/parameters. We maintain a history of kcopyd usage by each module in the variables io_period and total_period in struct dm_kcopyd_throttle. The actual kcopyd activity is calculated as a percentage of time equal to "(100 * io_period / total_period)". This is compared with the user-defined throttle percentage threshold and if it is exceeded, we sleep. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
89 lines
2.8 KiB
C
89 lines
2.8 KiB
C
/*
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* Copyright (C) 2001 - 2003 Sistina Software
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* Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
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*
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* kcopyd provides a simple interface for copying an area of one
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* block-device to one or more other block-devices, either synchronous
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* or with an asynchronous completion notification.
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*
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* This file is released under the GPL.
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*/
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#ifndef _LINUX_DM_KCOPYD_H
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#define _LINUX_DM_KCOPYD_H
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#ifdef __KERNEL__
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#include <linux/dm-io.h>
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/* FIXME: make this configurable */
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#define DM_KCOPYD_MAX_REGIONS 8
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#define DM_KCOPYD_IGNORE_ERROR 1
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struct dm_kcopyd_throttle {
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unsigned throttle;
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unsigned num_io_jobs;
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unsigned io_period;
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unsigned total_period;
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unsigned last_jiffies;
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};
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/*
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* kcopyd clients that want to support throttling must pass an initialised
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* dm_kcopyd_throttle struct into dm_kcopyd_client_create().
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* Two or more clients may share the same instance of this struct between
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* them if they wish to be throttled as a group.
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*
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* This macro also creates a corresponding module parameter to configure
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* the amount of throttling.
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*/
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#define DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(name, description) \
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static struct dm_kcopyd_throttle dm_kcopyd_throttle = { 100, 0, 0, 0, 0 }; \
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module_param_named(name, dm_kcopyd_throttle.throttle, uint, 0644); \
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MODULE_PARM_DESC(name, description)
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/*
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* To use kcopyd you must first create a dm_kcopyd_client object.
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* throttle can be NULL if you don't want any throttling.
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*/
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struct dm_kcopyd_client;
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struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle);
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void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc);
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/*
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* Submit a copy job to kcopyd. This is built on top of the
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* previous three fns.
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*
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* read_err is a boolean,
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* write_err is a bitset, with 1 bit for each destination region
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*/
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typedef void (*dm_kcopyd_notify_fn)(int read_err, unsigned long write_err,
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void *context);
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int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
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unsigned num_dests, struct dm_io_region *dests,
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unsigned flags, dm_kcopyd_notify_fn fn, void *context);
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/*
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* Prepare a callback and submit it via the kcopyd thread.
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*
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* dm_kcopyd_prepare_callback allocates a callback structure and returns it.
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* It must not be called from interrupt context.
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* The returned value should be passed into dm_kcopyd_do_callback.
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*
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* dm_kcopyd_do_callback submits the callback.
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* It may be called from interrupt context.
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* The callback is issued from the kcopyd thread.
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*/
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void *dm_kcopyd_prepare_callback(struct dm_kcopyd_client *kc,
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dm_kcopyd_notify_fn fn, void *context);
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void dm_kcopyd_do_callback(void *job, int read_err, unsigned long write_err);
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int dm_kcopyd_zero(struct dm_kcopyd_client *kc,
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unsigned num_dests, struct dm_io_region *dests,
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unsigned flags, dm_kcopyd_notify_fn fn, void *context);
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#endif /* __KERNEL__ */
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#endif /* _LINUX_DM_KCOPYD_H */
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