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[dm-devel] [PATCH 2/2] dm-ioband: I/O bandwidth controller v1.12.0: range-bw



range-bw was implemented as another I/O scheduling policy of dm-ioband
to support predicable I/O bandwidth between minimum and maximum
bandwidth defined by administrator. Here, minimum I/O bandwidth should
be guaranteed for stable performance or reliability of specific
process groups and I/O bandwidth over maximum should be throttled to
protect the limited I/O resource from over-provisioning in unnecessary
usage or to reserve the I/O bandwidth for another use.

Signed-off-by: Dong-Jae Kang <baramsori72 gmail com>

---
 Documentation/device-mapper/range-bw.txt |   99 ++++
 drivers/md/dm-ioband-rangebw.c           |  678 +++++++++++++++++++++++++++++++
 2 files changed, 777 insertions(+)

Index: linux-2.6.30/drivers/md/dm-ioband-rangebw.c
===================================================================
--- /dev/null
+++ linux-2.6.30/drivers/md/dm-ioband-rangebw.c
@@ -0,0 +1,678 @@
+/*
+ * dm-ioband-rangebw.c
+ *
+ * This is a I/O control policy to support the Range Bandwidth in Disk I/O.
+ * And this policy is for dm-ioband controller by Ryo Tsuruta,
+ * Hirokazu Takahashi
+ *
+ * Copyright (C) 2008 - 2011
+ * Electronics and Telecommunications Research Institute(ETRI)
+ *
+ * This program is free software. you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License(GPL) as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Contact Information:
+ * Dong-Jae, Kang <djkang etri re kr>, Chei-Yol,Kim <gauri etri re kr>,
+ * Sung-In,Jung <sijung etri re kr>
+ */
+
+#include <linux/bio.h>
+#include <linux/workqueue.h>
+#include <linux/rbtree.h>
+#include "dm.h"
+#include "md.h"
+#include "dm-ioband.h"
+
+static void range_bw_timeover(unsigned long);
+static void range_bw_timer_register(struct timer_list *,
+					 unsigned long, unsigned long);
+
+/*
+ * Functions for Range Bandwidth(range-bw) policy based on
+ * the time slice and token.
+ */
+#define DEFAULT_BUCKET          2
+#define DEFAULT_TOKENPOOL       2048
+
+#define TIME_SLICE_EXPIRED      1
+#define TIME_SLICE_NOT_EXPIRED  0
+
+#define MINBW_IO_MODE           0
+#define LEFTOVER_IO_MODE        1
+#define RANGE_IO_MODE           2
+#define DEFAULT_IO_MODE         3
+#define NO_IO_MODE 	        4
+
+#define MINBW_PRIO_BASE         10
+#define OVER_IO_RATE		4
+
+#define DEFAULT_RANGE_BW        "0:0"
+#define DEFAULT_MIN_BW          0
+#define DEFAULT_MAX_BW          0
+#define POLICY_PARAM_DELIM "=:,"
+
+static const int time_slice_base = HZ / 10;
+static const int range_time_slice_base = HZ / 50;
+static void do_nothing(void) {}
+/*
+ * g_restart_bios function for range-bw policy
+ */
+static int range_bw_restart_bios(struct ioband_device *dp)
+{
+	return 1;
+}
+
+/*
+ * Allocate the time slice when IO mode is MINBW_IO_MODE,
+ * RANGE_IO_MODE or LEFTOVER_IO_MODE
+ */
+static int set_time_slice(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int dp_io_mode, gp_io_mode;
+	unsigned long now = jiffies;
+
+	dp_io_mode = dp->g_io_mode;
+	gp_io_mode = gp->c_io_mode;
+
+	gp->c_time_slice_start = now;
+
+	if (dp_io_mode == LEFTOVER_IO_MODE) {
+		gp->c_time_slice_end = now + gp->c_time_slice;
+		return 0;
+	}
+
+	if (gp_io_mode == MINBW_IO_MODE)
+		gp->c_time_slice_end = now + gp->c_time_slice;
+	else if (gp_io_mode == RANGE_IO_MODE)
+		gp->c_time_slice_end = now + range_time_slice_base;
+	else if (gp_io_mode == DEFAULT_IO_MODE)
+		gp->c_time_slice_end = now + time_slice_base;
+	else if (gp_io_mode == NO_IO_MODE) {
+		gp->c_time_slice_end = 0;
+		gp->c_time_slice_expired = TIME_SLICE_EXPIRED;
+		return 0;
+	}
+
+	gp->c_time_slice_expired = TIME_SLICE_NOT_EXPIRED;
+
+	return 0;
+}
+
+/*
+ * Calculate the priority of given ioband_group
+ */
+static int range_bw_priority(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int prio = 0;
+
+	if (dp->g_io_mode == LEFTOVER_IO_MODE) {
+		prio = random32() % MINBW_PRIO_BASE;
+		if (prio == 0)
+			prio = 1;
+	} else if (gp->c_io_mode == MINBW_IO_MODE) {
+		prio = (gp->c_min_bw_token - gp->c_consumed_min_bw_token) *
+							 MINBW_PRIO_BASE;
+	} else if (gp->c_io_mode == DEFAULT_IO_MODE) {
+		prio = MINBW_PRIO_BASE;
+	} else if (gp->c_io_mode == RANGE_IO_MODE) {
+		prio = MINBW_PRIO_BASE / 2;
+	} else {
+		prio = 0;
+	}
+
+	return prio;
+}
+
+/*
+ * Check whether this group has right to issue an I/O in range-bw policy mode.
+ *  Return 0 if it doesn't have right, otherwise return the non-zero value.
+ */
+static int has_right_to_issue(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int prio;
+
+	if (gp->c_prio_blocked > 0 || gp->c_blocked - gp->c_prio_blocked > 0) {
+		prio = range_bw_priority(gp);
+		if (prio <= 0)
+			return 1;
+		return prio;
+	}
+
+	if (gp == dp->g_running_gp) {
+
+		if (gp->c_time_slice_expired == TIME_SLICE_EXPIRED) {
+
+			gp->c_time_slice_expired = TIME_SLICE_NOT_EXPIRED;
+			gp->c_time_slice_end = 0;
+
+			return 0;
+		}
+
+		if (gp->c_time_slice_end == 0)
+			set_time_slice(gp);
+
+		return range_bw_priority(gp);
+
+	}
+
+	dp->g_running_gp = gp;
+	set_time_slice(gp);
+
+	return range_bw_priority(gp);
+}
+
+/*
+ * Reset all variables related with range-bw token and time slice
+ */
+static int reset_range_bw_token(struct ioband_group *gp, unsigned long now)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+
+	list_for_each_entry(p, &dp->g_groups, c_list) {
+		p->c_consumed_min_bw_token = 0;
+		p->c_is_over_max_bw = MAX_BW_UNDER;
+		if (p->c_io_mode != DEFAULT_IO_MODE)
+			p->c_io_mode = MINBW_IO_MODE;
+	}
+
+	dp->g_consumed_min_bw_token = 0;
+
+	dp->g_next_time_period = now + HZ;
+	dp->g_time_period_expired = TIME_SLICE_NOT_EXPIRED;
+	dp->g_io_mode = MINBW_IO_MODE;
+
+	list_for_each_entry(p, &dp->g_groups, c_list) {
+		if (waitqueue_active(&p->c_max_bw_over_waitq))
+			wake_up_all(&p->c_max_bw_over_waitq);
+	}
+	return 0;
+}
+
+/*
+ * Use tokens(Increase the number of consumed token) to issue an I/O
+ * for guranteeing the range-bw. and check the expiration of local and
+ * global time slice, and overflow of max bw
+ */
+static int range_bw_consume_token(struct ioband_group *gp, int count, int flag)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+	unsigned long now = jiffies;
+	int io_mode;
+
+	dp->g_current = gp;
+
+	if (dp->g_next_time_period == 0) {
+		dp->g_next_time_period = now + HZ;
+		dp->g_time_period_expired = TIME_SLICE_NOT_EXPIRED;
+	}
+
+	if (time_after(now, dp->g_next_time_period)) {
+		reset_range_bw_token(gp, now);
+	} else {
+		gp->c_consumed_min_bw_token += count;
+		dp->g_consumed_min_bw_token += count;
+
+		if (gp->c_max_bw > 0 && gp->c_consumed_min_bw_token >=
+							gp->c_max_bw_token) {
+			gp->c_is_over_max_bw = MAX_BW_OVER;
+			gp->c_io_mode = NO_IO_MODE;
+			return R_YIELD;
+		}
+
+		if (gp->c_io_mode != RANGE_IO_MODE && gp->c_min_bw_token <=
+						gp->c_consumed_min_bw_token) {
+			gp->c_io_mode = RANGE_IO_MODE;
+
+			if (dp->g_total_min_bw_token <=
+						dp->g_consumed_min_bw_token) {
+				list_for_each_entry(p, &dp->g_groups, c_list) {
+					if (p->c_io_mode == RANGE_IO_MODE ||
+					    p->c_io_mode == DEFAULT_IO_MODE) {
+						io_mode = 1;
+					} else {
+						io_mode = 0;
+						break;
+					}
+				}
+
+				if (io_mode && dp->g_io_mode == MINBW_IO_MODE)
+					dp->g_io_mode = LEFTOVER_IO_MODE;
+			}
+		}
+	}
+
+	if (gp->c_time_slice_end != 0 &&
+	    time_after(now, gp->c_time_slice_end)) {
+		gp->c_time_slice_expired = TIME_SLICE_EXPIRED;
+		return R_YIELD;
+	}
+
+	return R_OK;
+}
+
+static int is_no_io_mode(struct ioband_group *gp)
+{
+	if (gp->c_io_mode == NO_IO_MODE)
+		return 1;
+
+	return 0;
+}
+
+/*
+ * Check if this group is able to receive a new bio.
+ * in range bw policy, we only check that ioband device should be blocked
+ */
+static int range_bw_queue_full(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	unsigned long now, time_step;
+
+	if (is_no_io_mode(gp)) {
+		now = jiffies;
+		if (time_after(dp->g_next_time_period, now)) {
+			time_step = dp->g_next_time_period - now;
+			range_bw_timer_register(gp->c_timer,
+						(time_step + TIME_COMPENSATOR),
+						(unsigned long)gp);
+			wait_event_lock_irq(gp->c_max_bw_over_waitq,
+					    !is_no_io_mode(gp),
+					    dp->g_lock, do_nothing());
+		}
+	}
+
+	return (gp->c_blocked >= gp->c_limit);
+}
+
+/*
+ * Convert the bw valuse to the number of bw token
+ * bw : Kbyte unit bandwidth
+ * token_base : the number of tokens used for one 1Kbyte-size IO
+ * -- Attention : Currently, We support the 512byte or 1Kbyte per 1 token
+ */
+static int convert_bw_to_token(int bw, int token_unit)
+{
+	int token;
+	int token_base;
+
+	token_base = (1 << token_unit) / 4;
+	token = bw * token_base;
+
+	return token;
+}
+
+
+/*
+ * Allocate the time slice for MINBW_IO_MODE to each group
+ */
+static void range_bw_time_slice_init(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+
+	list_for_each_entry(p, &dp->g_groups, c_list) {
+
+		if (dp->g_min_bw_total == 0)
+			p->c_time_slice = time_slice_base;
+		else
+			p->c_time_slice = time_slice_base +
+				((time_slice_base *
+				  ((p->c_min_bw + p->c_max_bw) / 2)) /
+					 dp->g_min_bw_total);
+	}
+}
+
+/*
+ *  Allocate the range_bw and range_bw_token to the given group
+ */
+static void set_range_bw(struct ioband_group *gp, int new_min, int new_max)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+	int token_unit;
+
+	dp->g_min_bw_total += (new_min - gp->c_min_bw);
+	gp->c_min_bw = new_min;
+
+	dp->g_max_bw_total += (new_max - gp->c_max_bw);
+	gp->c_max_bw = new_max;
+
+	if (new_min)
+		gp->c_io_mode = MINBW_IO_MODE;
+	else
+		gp->c_io_mode = DEFAULT_IO_MODE;
+
+	range_bw_time_slice_init(gp);
+
+	token_unit = dp->g_token_unit;
+	gp->c_min_bw_token = convert_bw_to_token(new_min, token_unit);
+	dp->g_total_min_bw_token =
+		convert_bw_to_token(dp->g_min_bw_total, token_unit);
+
+	gp->c_max_bw_token = convert_bw_to_token(new_max, token_unit);
+
+	if (dp->g_min_bw_total == 0) {
+		list_for_each_entry(p, &dp->g_groups, c_list)
+			p->c_limit = 1;
+	} else {
+		list_for_each_entry(p, &dp->g_groups, c_list) {
+			p->c_limit = dp->g_io_limit * 2 * p->c_min_bw /
+				dp->g_min_bw_total / OVER_IO_RATE + 1;
+		}
+	}
+
+	return;
+}
+
+/*
+ * Allocate the min_bw and min_bw_token to the given group
+ */
+static void set_min_bw(struct ioband_group *gp, int new)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+	int token_unit;
+
+	dp->g_min_bw_total += (new - gp->c_min_bw);
+	gp->c_min_bw = new;
+
+	if (new)
+		gp->c_io_mode = MINBW_IO_MODE;
+	else
+		gp->c_io_mode = DEFAULT_IO_MODE;
+
+	range_bw_time_slice_init(gp);
+
+	token_unit = dp->g_token_unit;
+	gp->c_min_bw_token = convert_bw_to_token(gp->c_min_bw, token_unit);
+	dp->g_total_min_bw_token =
+		convert_bw_to_token(dp->g_min_bw_total, token_unit);
+
+	if (dp->g_min_bw_total == 0) {
+		list_for_each_entry(p, &dp->g_groups, c_list)
+			p->c_limit = 1;
+	} else {
+		list_for_each_entry(p, &dp->g_groups, c_list) {
+			p->c_limit = dp->g_io_limit * 2 * p->c_min_bw /
+				dp->g_min_bw_total / OVER_IO_RATE + 1;
+		}
+	}
+
+	return;
+}
+
+/*
+ * Allocate the max_bw and max_bw_token to the pointed group
+ */
+static void set_max_bw(struct ioband_group *gp, int new)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int token_unit;
+
+	token_unit = dp->g_token_unit;
+
+	dp->g_max_bw_total += (new - gp->c_max_bw);
+	gp->c_max_bw = new;
+	gp->c_max_bw_token = convert_bw_to_token(new, token_unit);
+
+	range_bw_time_slice_init(gp);
+
+	return;
+
+}
+
+static void init_range_bw_token_bucket(struct ioband_device *dp, int val)
+{
+	dp->g_token_bucket = (dp->g_io_limit * 2 * DEFAULT_BUCKET) <<
+							dp->g_token_unit;
+	if (!val)
+		val = DEFAULT_TOKENPOOL << dp->g_token_unit;
+	if (val < dp->g_token_bucket)
+		val = dp->g_token_bucket;
+	dp->g_carryover = val/dp->g_token_bucket;
+	dp->g_token_left = 0;
+}
+
+static int policy_range_bw_param(struct ioband_group *gp,
+							char *cmd, char *value)
+{
+	long val = 0;
+	int r = 0;
+	int err = 0, err1, err2;
+	char *min, *max;
+	long min_val, max_val;
+
+	if (value) {
+		min = strsep(&value, POLICY_PARAM_DELIM);
+		max = strsep(&value, POLICY_PARAM_DELIM);
+		if (!min || !max)
+			err = 1;
+		else {
+			err1 = strict_strtol(min, 0, &min_val);
+			err2 = strict_strtol(max, 0, &max_val);
+			err = (err1 || err2);
+		}
+	} else {
+		min_val = DEFAULT_MIN_BW;
+		max_val = DEFAULT_MAX_BW;
+	}
+
+	if (!strcmp(cmd, "range-bw")) {
+		if (!err && 0 <= min_val &&
+		    min_val <= (INT_MAX / 2) &&	0 <= max_val &&
+		    max_val <= (INT_MAX / 2) && min_val <= max_val)
+			set_range_bw(gp, min_val, max_val);
+		else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "min-bw")) {
+		if (!err && 0 <= val && val <= (INT_MAX / 2))
+			set_min_bw(gp, val);
+		else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "max-bw")) {
+		if ((!err && 0 <= val && val <= (INT_MAX / 2) &&
+		     gp->c_min_bw <= val) || val == 0)
+			set_max_bw(gp, val);
+		else
+			r = -EINVAL;
+	} else {
+		r = -EINVAL;
+	}
+	return r;
+}
+
+static int policy_range_bw_ctr(struct ioband_group *gp, char *arg)
+{
+	int ret;
+
+	init_waitqueue_head(&gp->c_max_bw_over_waitq);
+	spin_lock_init(&gp->c_lock);
+
+	gp->c_min_bw = 0;
+	gp->c_max_bw = 0;
+	gp->c_io_mode = DEFAULT_IO_MODE;
+	gp->c_time_slice_expired = TIME_SLICE_NOT_EXPIRED;
+	gp->c_min_bw_token = 0;
+	gp->c_max_bw_token = 0;
+	gp->c_consumed_min_bw_token = 0;
+	gp->c_is_over_max_bw = MAX_BW_UNDER;
+	gp->c_time_slice_start = 0;
+	gp->c_time_slice_end = 0;
+	gp->c_wait_p_count = 0;
+
+	gp->c_time_slice = time_slice_base;
+
+	gp->c_timer = kmalloc(sizeof(struct timer_list), GFP_KERNEL);
+	if (gp->c_timer == NULL)
+		return -EINVAL;
+	memset(gp->c_timer, 0, sizeof(struct timer_list));
+	gp->timer_set = 0;
+
+	ret = policy_range_bw_param(gp, "range-bw", arg);
+
+	return ret;
+}
+
+static void policy_range_bw_dtr(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	gp->c_time_slice = 0;
+	set_range_bw(gp, 0, 0);
+
+	dp->g_running_gp = NULL;
+
+	if (gp->c_timer != NULL) {
+		del_timer(gp->c_timer);
+		kfree(gp->c_timer);
+	}
+}
+
+static void policy_range_bw_show(struct ioband_group *gp, int *szp,
+					char *result, unsigned int maxlen)
+{
+	struct ioband_group *p;
+	struct ioband_device *dp = gp->c_banddev;
+	struct rb_node *node;
+	int sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d :%d:%d", dp->g_token_bucket * dp->g_carryover,
+						gp->c_min_bw, gp->c_max_bw);
+
+	for (node = rb_first(&gp->c_group_root); node; node = rb_next(node)) {
+		p = rb_entry(node, struct ioband_group, c_group_node);
+		DMEMIT(" %d:%d:%d", p->c_id, p->c_min_bw, p->c_max_bw);
+	}
+	*szp = sz;
+}
+
+static int range_bw_prepare_token(struct ioband_group *gp,
+						struct bio *bio, int flag)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int unit;
+	int bio_count;
+	int token_count = 0;
+
+	unit = (1 << dp->g_token_unit);
+	bio_count = bio_sectors(bio);
+
+	if (unit == 8)
+		token_count = bio_count;
+	else if (unit == 4)
+		token_count = bio_count / 2;
+	else if (unit == 2)
+		token_count = bio_count / 4;
+	else if (unit == 1)
+		token_count = bio_count / 8;
+
+	return range_bw_consume_token(gp, token_count, flag);
+}
+
+void range_bw_timer_register(struct timer_list *ptimer,
+				unsigned long timeover, unsigned long  gp)
+{
+	struct ioband_group *group = (struct ioband_group *)gp;
+
+	if (group->timer_set == 0) {
+		init_timer(ptimer);
+		ptimer->expires = get_jiffies_64() + timeover;
+		ptimer->data = gp;
+		ptimer->function = range_bw_timeover;
+		add_timer(ptimer);
+		group->timer_set = 1;
+	}
+}
+
+/*
+ * Timer Handler function to protect the all processes's hanging in
+ * lower min-bw configuration
+ */
+void range_bw_timeover(unsigned long gp)
+{
+	struct ioband_group *group = (struct ioband_group *)gp;
+
+	if (group->c_is_over_max_bw == MAX_BW_OVER)
+		group->c_is_over_max_bw = MAX_BW_UNDER;
+
+	if (group->c_io_mode == NO_IO_MODE)
+		group->c_io_mode = MINBW_IO_MODE;
+
+	if (waitqueue_active(&group->c_max_bw_over_waitq))
+		wake_up_all(&group->c_max_bw_over_waitq);
+
+	group->timer_set = 0;
+}
+
+/*
+ *  <Method>      <description>
+ * g_can_submit   : To determine whether a given group has the right to
+ *                  submit BIOs. The larger the return value the higher the
+ *                  priority to submit. Zero means it has no right.
+ * g_prepare_bio  : Called right before submitting each BIO.
+ * g_restart_bios : Called if this ioband device has some BIOs blocked but none
+ *                  of them can be submitted now. This method has to
+ *                  reinitialize the data to restart to submit BIOs and return
+ *                  0 or 1.
+ *                  The return value 0 means that it has become able to submit
+ *                  them now so that this ioband device will continue its work.
+ *                  The return value 1 means that it is still unable to submit
+ *                  them so that this device will stop its work. And this
+ *                  policy module has to reactivate the device when it gets
+ *                  to be able to submit BIOs.
+ * g_hold_bio     : To hold a given BIO until it is submitted.
+ *                  The default function is used when this method is undefined.
+ * g_pop_bio      : To select and get the best BIO to submit.
+ * g_group_ctr    : To initalize the policy own members of struct ioband_group.
+ * g_group_dtr    : Called when struct ioband_group is removed.
+ * g_set_param    : To update the policy own date.
+ *                  The parameters can be passed through "dmsetup message"
+ *                  command.
+ * g_should_block : Called every time this ioband device receive a BIO.
+ *                  Return 1 if a given group can't receive any more BIOs,
+ *                  otherwise return 0.
+ * g_show         : Show the configuration.
+ */
+
+int policy_range_bw_init(struct ioband_device *dp, int argc, char **argv)
+{
+	long val;
+	int r = 0;
+
+	if (argc < 1)
+		val = 0;
+	else {
+		r = strict_strtol(argv[0], 0, &val);
+		if (r || val < 0)
+			return -EINVAL;
+	}
+
+	dp->g_can_submit = has_right_to_issue;
+	dp->g_prepare_bio = range_bw_prepare_token;
+	dp->g_restart_bios = range_bw_restart_bios;
+	dp->g_group_ctr = policy_range_bw_ctr;
+	dp->g_group_dtr = policy_range_bw_dtr;
+	dp->g_set_param = policy_range_bw_param;
+	dp->g_should_block = range_bw_queue_full;
+	dp->g_show = policy_range_bw_show;
+
+	dp->g_min_bw_total = 0;
+	dp->g_running_gp = NULL;
+	dp->g_total_min_bw_token = 0;
+	dp->g_io_mode = MINBW_IO_MODE;
+	dp->g_consumed_min_bw_token = 0;
+	dp->g_current = NULL;
+	dp->g_next_time_period = 0;
+	dp->g_time_period_expired = TIME_SLICE_NOT_EXPIRED;
+
+	dp->g_token_unit = PAGE_SHIFT - 9;
+	init_range_bw_token_bucket(dp, val);
+
+	return 0;
+}
Index: linux-2.6.30/Documentation/device-mapper/range-bw.txt
===================================================================
--- /dev/null
+++ linux-2.6.30/Documentation/device-mapper/range-bw.txt
@@ -0,0 +1,99 @@
+Range-BW I/O controller by Dong-Jae Kang <djkang etri re kr>
+
+
+1. Introduction
+===============
+
+The design of Range-BW is related with three another parts, Cgroup,
+bio-cgroup (or blkio-cgroup) and dm-ioband and it was implemented as
+an additional controller for dm-ioband.
+Cgroup framework is used to support process grouping mechanism and
+bio-cgroup is used to control delayed I/O or non-direct I/O. Finally,
+dm-ioband is a kind of I/O controller allowing the proportional I/O
+bandwidth to process groups based on its priority.
+The supposed controller supports the process group-based range
+bandwidth according to the priority or importance of the group. Range
+bandwidth means the predicable I/O bandwidth with minimum and maximum
+value defined by administrator.
+
+Minimum I/O bandwidth should be guaranteed for stable performance or
+reliability of specific service and I/O bandwidth over maximum should
+be throttled to protect the limited I/O resource from
+over-provisioning in unnecessary usage or to reserve the I/O bandwidth
+for another use.
+So, Range-BW was implemented to include the two concepts, guaranteeing
+of minimum I/O requirement and limitation of unnecessary bandwidth
+depending on its priority.
+And it was implemented as device mapper driver such like dm-ioband.
+So, it is independent of the underlying specific I/O scheduler, for
+example, CFQ, AS, NOOP, deadline and so on.
+
+* Attention
+Range-BW supports the predicable I/O bandwidth, but it should be
+configured in the scope of total I/O bandwidth of the I/O system to
+guarantee the minimum I/O requirement. For example, if total I/O
+bandwidth is 40Mbytes/sec,
+
+the summary of I/O bandwidth configured in each process group should
+be equal or smaller than 40Mbytes/sec.
+So, we need to check total I/O bandwidth before set it up.
+
+2. Setup and Installation
+=========================
+
+This part is same with dm-ioband,
+../../Documentation/device-mapper/ioband.txt or
+http://sourceforge.net/apps/trac/ioband/wiki/dm-ioband/man/setup
+except the allocation of range-bw values.
+
+3. Usage
+========
+
+It is very useful to refer the documentation for dm-ioband in
+../../Documentation/device-mapper/ioband.txt or
+
+http://sourceforge.net/apps/trac/ioband/wiki/dm-ioband, because
+Range-BW follows the basic semantics of dm-ioband.
+This example is for range-bw configuration.
+
+# mount the cgroup
+mount -t cgroup -o blkio none /root/cgroup/blkio
+
+# create the process groups (3 groups)
+mkdir /root/cgroup/blkio/bgroup1
+mkdir /root/cgroup/blkio/bgroup2
+mkdir /root/cgroup/blkio/bgroup3
+
+# create the ioband device ( name : ioband1 )
+echo "0 $(blockdev --getsize /dev/sdb2) ioband /dev/sdb2 1 0 0 none
+range-bw 0 :0:0" | dmsetup create ioband1
+: Attention - device name (/dev/sdb2) should be modified depending on
+your system
+
+# init ioband device ( type and policy )
+dmsetup message ioband1 0 type cgroup
+dmsetup message ioband1 0 policy range-bw
+
+# attach the groups to the ioband device
+dmsetup message ioband1 0 attach 2
+dmsetup message ioband1 0 attach 3
+dmsetup message ioband1 0 attach 4
+: group number can be referred in /root/cgroup/blkio/bgroup1/blkio.id
+
+# allocate the values ( range-bw ) : XXX Kbytes
+: the sum of minimum I/O bandwidth in each group should be equal or
+smaller than total bandwidth to be supported by your system
+
+# range : about 100~500 Kbytes
+dmsetup message ioband1 0 range-bw 2:100:500
+
+# range : about 700~1000 Kbytes
+dmsetup message ioband1 0 range-bw 3:700:1000
+
+# range : about 30~35Mbytes
+dmsetup message ioband1 0 range-bw 4:30000:35000
+
+You can confirm the configuration of range-bw by using this command :
+[root localhost range-bw]# dmsetup table --target ioband
+ioband1: 0 305235000 ioband 8:18 1 4 128 cgroup \
+    range-bw 16384 :0:0 2:100:500 3:700:1000 4:30000:35000


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