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Message-ID: <9ea3761d048bf6b5f36c3d57e3eecbce2780b6c3.1453308862.git.shli@fb.com>
Date: Wed, 20 Jan 2016 09:49:18 -0800
From: Shaohua Li <shli@...com>
To: <linux-kernel@...r.kernel.org>
CC: <axboe@...nel.dk>, <tj@...nel.org>, <vgoyal@...hat.com>,
<jmoyer@...hat.com>, <Kernel-team@...com>
Subject: [RFC 2/3] blk-throttling: weight based throttling
We know total bandwidth of a disk and can calculate cgroup's bandwidth
percentage against disk bandwidth according to its weight. We can easily
calculate cgroup bandwidth.
Signed-off-by: Shaohua Li <shli@...com>
---
block/blk-throttle.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 134 insertions(+), 1 deletion(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 2149a1d..b3f847d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -12,6 +12,9 @@
#include <linux/blk-cgroup.h>
#include "blk.h"
+#define MAX_WEIGHT (1000)
+#define WEIGHT_RATIO_SHIFT (12)
+#define WEIGHT_RATIO (1 << WEIGHT_RATIO_SHIFT)
/* Max dispatch from a group in 1 round */
static int throtl_grp_quantum = 8;
@@ -74,6 +77,10 @@ struct throtl_service_queue {
unsigned int nr_pending; /* # queued in the tree */
unsigned long first_pending_disptime; /* disptime of the first tg */
struct timer_list pending_timer; /* fires on first_pending_disptime */
+
+ unsigned int weight;
+ unsigned int children_weight;
+ unsigned int ratio;
};
enum tg_state_flags {
@@ -152,6 +159,9 @@ struct throtl_data
/* Work for dispatching throttled bios */
struct work_struct dispatch_work;
+
+ bool bw_based;
+ bool weight_based;
};
static void throtl_pending_timer_fn(unsigned long arg);
@@ -203,6 +213,15 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
return container_of(sq, struct throtl_data, service_queue);
}
+static inline uint64_t queue_bandwidth(struct throtl_data *td, int rw)
+{
+ uint64_t bw = td->queue->avg_bw[rw] * 512;
+
+ /* give extra bw, so cgroup can dispatch enough IO */
+ bw += bw >> 3;
+ return bw;
+}
+
/**
* throtl_log - log debug message via blktrace
* @sq: the service_queue being reported
@@ -371,6 +390,7 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
sq->parent_sq = &td->service_queue;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
+ sq->parent_sq->children_weight += sq->weight;
tg->td = td;
}
@@ -386,7 +406,8 @@ static void tg_update_has_rules(struct throtl_grp *tg)
for (rw = READ; rw <= WRITE; rw++)
tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
- (tg->bps[rw] != -1 || tg->iops[rw] != -1);
+ (tg->bps[rw] != -1 || tg->iops[rw] != -1 ||
+ tg->service_queue.weight);
}
static void throtl_pd_online(struct blkg_policy_data *pd)
@@ -401,6 +422,10 @@ static void throtl_pd_online(struct blkg_policy_data *pd)
static void throtl_pd_free(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
+ struct throtl_service_queue *sq = &tg->service_queue;
+
+ if (sq->parent_sq)
+ sq->parent_sq->children_weight -= sq->weight;
del_timer_sync(&tg->service_queue.pending_timer);
kfree(tg);
@@ -898,6 +923,48 @@ static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
}
+static void tg_update_bps(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *sq, *parent_sq;
+
+ sq = &tg->service_queue;
+ parent_sq = sq->parent_sq;
+
+ if (!tg->td->weight_based || !parent_sq)
+ return;
+ sq->ratio = max_t(unsigned int,
+ parent_sq->ratio * sq->weight / parent_sq->children_weight,
+ 1);
+
+ tg->bps[READ] = max_t(uint64_t,
+ (queue_bandwidth(tg->td, READ) * sq->ratio) >>
+ WEIGHT_RATIO_SHIFT,
+ 1024);
+ tg->bps[WRITE] = max_t(uint64_t,
+ (queue_bandwidth(tg->td, WRITE) * sq->ratio) >>
+ WEIGHT_RATIO_SHIFT,
+ 1024);
+}
+
+static void tg_update_ratio(struct throtl_grp *tg)
+{
+ struct throtl_data *td = tg->td;
+ struct cgroup_subsys_state *pos_css;
+ struct blkcg_gq *blkg;
+
+ blkg_for_each_descendant_pre(blkg, pos_css, td->queue->root_blkg) {
+ struct throtl_service_queue *sq;
+
+ tg = blkg_to_tg(blkg);
+ sq = &tg->service_queue;
+
+ if (!sq->parent_sq)
+ continue;
+
+ tg_update_bps(tg);
+ }
+}
+
static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
{
struct throtl_service_queue *sq = &tg->service_queue;
@@ -1202,12 +1269,65 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
v = -1;
tg = blkg_to_tg(ctx.blkg);
+ if (tg->td->weight_based) {
+ ret = -EBUSY;
+ goto out_finish;
+ }
if (is_u64)
*(u64 *)((void *)tg + of_cft(of)->private) = v;
else
*(unsigned int *)((void *)tg + of_cft(of)->private) = v;
+ tg->td->bw_based = true;
+
+ tg_conf_updated(tg);
+ ret = 0;
+out_finish:
+ blkg_conf_finish(&ctx);
+ return ret ?: nbytes;
+}
+
+static ssize_t tg_set_weight(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct blkcg *blkcg = css_to_blkcg(of_css(of));
+ struct blkg_conf_ctx ctx;
+ struct throtl_grp *tg;
+ int ret;
+ u64 v;
+ int old_weight;
+
+ ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
+ if (ret)
+ return ret;
+ ret = -EINVAL;
+ if (sscanf(ctx.body, "%llu", &v) != 1)
+ goto out_finish;
+ if (v > MAX_WEIGHT)
+ v = MAX_WEIGHT;
+ if (v == 0)
+ v = 1;
+
+ tg = blkg_to_tg(ctx.blkg);
+ if (tg->td->bw_based) {
+ ret = -EBUSY;
+ goto out_finish;
+ }
+ tg->td->weight_based = true;
+
+ old_weight = tg->service_queue.weight;
+
+ tg->service_queue.weight = v;
+ if (tg->service_queue.parent_sq) {
+ struct throtl_service_queue *psq = tg->service_queue.parent_sq;
+ if (v > old_weight)
+ psq->children_weight += v - old_weight;
+ else if (v < old_weight)
+ psq->children_weight -= old_weight - v;
+ }
+
+ tg_update_ratio(tg);
tg_conf_updated(tg);
ret = 0;
out_finish:
@@ -1229,6 +1349,12 @@ static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
static struct cftype throtl_legacy_files[] = {
{
+ .name = "throttle.weight",
+ .private = offsetof(struct throtl_grp, service_queue.weight),
+ .seq_show = tg_print_conf_uint,
+ .write = tg_set_weight,
+ },
+ {
.name = "throttle.read_bps_device",
.private = offsetof(struct throtl_grp, bps[READ]),
.seq_show = tg_print_conf_u64,
@@ -1313,6 +1439,10 @@ static ssize_t tg_set_max(struct kernfs_open_file *of,
return ret;
tg = blkg_to_tg(ctx.blkg);
+ if (tg->td->weight_based) {
+ ret = -EBUSY;
+ goto out_finish;
+ }
v[0] = tg->bps[READ];
v[1] = tg->bps[WRITE];
@@ -1358,6 +1488,7 @@ static ssize_t tg_set_max(struct kernfs_open_file *of,
tg->bps[WRITE] = v[1];
tg->iops[READ] = v[2];
tg->iops[WRITE] = v[3];
+ tg->td->bw_based = true;
tg_conf_updated(tg);
ret = 0;
@@ -1415,6 +1546,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
sq = &tg->service_queue;
+ tg_update_bps(tg);
while (true) {
/* throtl is FIFO - if bios are already queued, should queue */
if (sq->nr_queued[rw])
@@ -1563,6 +1695,7 @@ int blk_throtl_init(struct request_queue *q)
INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
throtl_service_queue_init(&td->service_queue);
+ td->service_queue.ratio = WEIGHT_RATIO;
q->td = td;
td->queue = q;
--
2.4.6
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