diff mbox

[V5,03/17] blk-throttle: add .low interface

Message ID c4179e0d7e8f2e36455db1a639911ab9aca374b1.1481833017.git.shli@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Shaohua Li Dec. 15, 2016, 8:32 p.m. UTC 
Add low limit for cgroup and corresponding cgroup interface.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/blk-throttle.c | 134 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 106 insertions(+), 28 deletions(-)

Comments

Tejun Heo Jan. 9, 2017, 4:35 p.m. UTC | #1 
Happy new year, Shaohua.

Sorry about the long delay.

On Thu, Dec 15, 2016 at 12:32:54PM -0800, Shaohua Li wrote:
> Add low limit for cgroup and corresponding cgroup interface.

It'd be nice to explain why we're adding separate _conf fields.

> +static void blk_throtl_update_valid_limit(struct throtl_data *td)

I think blk_throtl_update_limit_valid() would be more consistent.

> +{
> +	struct cgroup_subsys_state *pos_css;
> +	struct blkcg_gq *blkg;
> +	bool low_valid = false;
> +
> +	rcu_read_lock();
> +	blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
> +		struct throtl_grp *tg = blkg_to_tg(blkg);
> +
> +		if (tg->bps[READ][LIMIT_LOW] != U64_MAX ||
> +		    tg->bps[WRITE][LIMIT_LOW] != U64_MAX ||
> +		    tg->iops[READ][LIMIT_LOW] != UINT_MAX ||
> +		    tg->iops[WRITE][LIMIT_LOW] != UINT_MAX)
> +			low_valid = true;

It's weird that it's defaulting to MAX.  Shouldn't it default to 0?
When we enable these limits on a cgroup, we want it to not affect the
operation without further configuration.  For max limit, MAX does that
as being over the limit is what changes the behavior.  For low, it's
the other way around.  We enforce latency target if cgroups are under
the low limit, and thus 0 should be the noop default value, which is
the same in memcg.

> +	}
> +	rcu_read_unlock();
> +
> +	if (low_valid)
> +		td->limit_valid[LIMIT_LOW] = true;
> +	else
> +		td->limit_valid[LIMIT_LOW] = false;

Maybe
	td->limit_valid[LIMIT_LOW] = low_valid;

Thanks.
diff mbox

Patch

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index a75bfa2..fcc4199 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -84,6 +84,7 @@  enum tg_state_flags {
 #define rb_entry_tg(node)	rb_entry((node), struct throtl_grp, rb_node)
 
 enum {
+	LIMIT_LOW,
 	LIMIT_MAX,
 	LIMIT_CNT,
 };
@@ -124,11 +125,15 @@  struct throtl_grp {
 	/* are there any throtl rules between this group and td? */
 	bool has_rules[2];
 
-	/* bytes per second rate limits */
+	/* internally used bytes per second rate limits */
 	uint64_t bps[2][LIMIT_CNT];
+	/* user configured bps limits */
+	uint64_t bps_conf[2][LIMIT_CNT];
 
-	/* IOPS limits */
+	/* internally used IOPS limits */
 	unsigned int iops[2][LIMIT_CNT];
+	/* user configured IOPS limits */
+	unsigned int iops_conf[2][LIMIT_CNT];
 
 	/* Number of bytes disptached in current slice */
 	uint64_t bytes_disp[2];
@@ -355,6 +360,8 @@  static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 		for (index = 0; index < LIMIT_CNT; index++) {
 			tg->bps[rw][index] = U64_MAX;
 			tg->iops[rw][index] = UINT_MAX;
+			tg->bps_conf[rw][index] = U64_MAX;
+			tg->iops_conf[rw][index] = UINT_MAX;
 		}
 	}
 
@@ -414,6 +421,46 @@  static void throtl_pd_online(struct blkg_policy_data *pd)
 	tg_update_has_rules(pd_to_tg(pd));
 }
 
+static void blk_throtl_update_valid_limit(struct throtl_data *td)
+{
+	struct cgroup_subsys_state *pos_css;
+	struct blkcg_gq *blkg;
+	bool low_valid = false;
+
+	rcu_read_lock();
+	blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
+		struct throtl_grp *tg = blkg_to_tg(blkg);
+
+		if (tg->bps[READ][LIMIT_LOW] != U64_MAX ||
+		    tg->bps[WRITE][LIMIT_LOW] != U64_MAX ||
+		    tg->iops[READ][LIMIT_LOW] != UINT_MAX ||
+		    tg->iops[WRITE][LIMIT_LOW] != UINT_MAX)
+			low_valid = true;
+	}
+	rcu_read_unlock();
+
+	if (low_valid)
+		td->limit_valid[LIMIT_LOW] = true;
+	else
+		td->limit_valid[LIMIT_LOW] = false;
+}
+
+static void throtl_pd_offline(struct blkg_policy_data *pd)
+{
+	struct throtl_grp *tg = pd_to_tg(pd);
+
+	tg->bps[READ][LIMIT_LOW] = U64_MAX;
+	tg->bps[WRITE][LIMIT_LOW] = U64_MAX;
+	tg->iops[READ][LIMIT_LOW] = UINT_MAX;
+	tg->iops[WRITE][LIMIT_LOW] = UINT_MAX;
+
+	blk_throtl_update_valid_limit(tg->td);
+
+	if (tg->td->limit_index == LIMIT_LOW &&
+	    !tg->td->limit_valid[LIMIT_LOW])
+		tg->td->limit_index = LIMIT_MAX;
+}
+
 static void throtl_pd_free(struct blkg_policy_data *pd)
 {
 	struct throtl_grp *tg = pd_to_tg(pd);
@@ -1284,7 +1331,7 @@  static struct cftype throtl_legacy_files[] = {
 	{ }	/* terminate */
 };
 
-static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
+static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
 			 int off)
 {
 	struct throtl_grp *tg = pd_to_tg(pd);
@@ -1294,38 +1341,38 @@  static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
 	if (!dname)
 		return 0;
 
-	if (tg->bps[READ][LIMIT_MAX] == U64_MAX &&
-	    tg->bps[WRITE][LIMIT_MAX] == U64_MAX &&
-	    tg->iops[READ][LIMIT_MAX] == UINT_MAX &&
-	    tg->iops[WRITE][LIMIT_MAX] == UINT_MAX)
+	if (tg->bps_conf[READ][off] == U64_MAX &&
+	    tg->bps_conf[WRITE][off] == U64_MAX &&
+	    tg->iops_conf[READ][off] == UINT_MAX &&
+	    tg->iops_conf[WRITE][off] == UINT_MAX)
 		return 0;
 
-	if (tg->bps[READ][LIMIT_MAX] != U64_MAX)
+	if (tg->bps_conf[READ][off] != U64_MAX)
 		snprintf(bufs[0], sizeof(bufs[0]), "%llu",
-			tg->bps[READ][LIMIT_MAX]);
-	if (tg->bps[WRITE][LIMIT_MAX] != U64_MAX)
+			tg->bps_conf[READ][off]);
+	if (tg->bps_conf[WRITE][off] != U64_MAX)
 		snprintf(bufs[1], sizeof(bufs[1]), "%llu",
-			tg->bps[WRITE][LIMIT_MAX]);
-	if (tg->iops[READ][LIMIT_MAX] != UINT_MAX)
+			tg->bps_conf[WRITE][off]);
+	if (tg->iops_conf[READ][off] != UINT_MAX)
 		snprintf(bufs[2], sizeof(bufs[2]), "%u",
-			tg->iops[READ][LIMIT_MAX]);
-	if (tg->iops[WRITE][LIMIT_MAX] != UINT_MAX)
+			tg->iops_conf[READ][off]);
+	if (tg->iops_conf[WRITE][off] != UINT_MAX)
 		snprintf(bufs[3], sizeof(bufs[3]), "%u",
-			tg->iops[WRITE][LIMIT_MAX]);
+			tg->iops_conf[WRITE][off]);
 
 	seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
 		   dname, bufs[0], bufs[1], bufs[2], bufs[3]);
 	return 0;
 }
 
-static int tg_print_max(struct seq_file *sf, void *v)
+static int tg_print_limit(struct seq_file *sf, void *v)
 {
-	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_max,
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
 			  &blkcg_policy_throtl, seq_cft(sf)->private, false);
 	return 0;
 }
 
-static ssize_t tg_set_max(struct kernfs_open_file *of,
+static ssize_t tg_set_limit(struct kernfs_open_file *of,
 			  char *buf, size_t nbytes, loff_t off)
 {
 	struct blkcg *blkcg = css_to_blkcg(of_css(of));
@@ -1333,6 +1380,7 @@  static ssize_t tg_set_max(struct kernfs_open_file *of,
 	struct throtl_grp *tg;
 	u64 v[4];
 	int ret;
+	int index = of_cft(of)->private;
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
 	if (ret)
@@ -1340,10 +1388,10 @@  static ssize_t tg_set_max(struct kernfs_open_file *of,
 
 	tg = blkg_to_tg(ctx.blkg);
 
-	v[0] = tg->bps[READ][LIMIT_MAX];
-	v[1] = tg->bps[WRITE][LIMIT_MAX];
-	v[2] = tg->iops[READ][LIMIT_MAX];
-	v[3] = tg->iops[WRITE][LIMIT_MAX];
+	v[0] = tg->bps_conf[READ][index];
+	v[1] = tg->bps_conf[WRITE][index];
+	v[2] = tg->iops_conf[READ][index];
+	v[3] = tg->iops_conf[WRITE][index];
 
 	while (true) {
 		char tok[27];	/* wiops=18446744073709551616 */
@@ -1380,11 +1428,31 @@  static ssize_t tg_set_max(struct kernfs_open_file *of,
 			goto out_finish;
 	}
 
-	tg->bps[READ][LIMIT_MAX] = v[0];
-	tg->bps[WRITE][LIMIT_MAX] = v[1];
-	tg->iops[READ][LIMIT_MAX] = v[2];
-	tg->iops[WRITE][LIMIT_MAX] = v[3];
+	tg->bps_conf[READ][index] = v[0];
+	tg->bps_conf[WRITE][index] = v[1];
+	tg->iops_conf[READ][index] = v[2];
+	tg->iops_conf[WRITE][index] = v[3];
 
+	if (index == LIMIT_MAX) {
+		tg->bps[READ][index] = v[0];
+		tg->bps[WRITE][index] = v[1];
+		tg->iops[READ][index] = v[2];
+		tg->iops[WRITE][index] = v[3];
+	}
+	tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
+		tg->bps_conf[READ][LIMIT_MAX]);
+	tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
+		tg->bps_conf[WRITE][LIMIT_MAX]);
+	tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
+		tg->iops_conf[READ][LIMIT_MAX]);
+	tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
+		tg->iops_conf[WRITE][LIMIT_MAX]);
+
+	if (index == LIMIT_LOW) {
+		blk_throtl_update_valid_limit(tg->td);
+		if (tg->td->limit_valid[LIMIT_LOW])
+			tg->td->limit_index = LIMIT_LOW;
+	}
 	tg_conf_updated(tg);
 	ret = 0;
 out_finish:
@@ -1394,10 +1462,18 @@  static ssize_t tg_set_max(struct kernfs_open_file *of,
 
 static struct cftype throtl_files[] = {
 	{
+		.name = "low",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = tg_print_limit,
+		.write = tg_set_limit,
+		.private = LIMIT_LOW,
+	},
+	{
 		.name = "max",
 		.flags = CFTYPE_NOT_ON_ROOT,
-		.seq_show = tg_print_max,
-		.write = tg_set_max,
+		.seq_show = tg_print_limit,
+		.write = tg_set_limit,
+		.private = LIMIT_MAX,
 	},
 	{ }	/* terminate */
 };
@@ -1416,6 +1492,7 @@  static struct blkcg_policy blkcg_policy_throtl = {
 	.pd_alloc_fn		= throtl_pd_alloc,
 	.pd_init_fn		= throtl_pd_init,
 	.pd_online_fn		= throtl_pd_online,
+	.pd_offline_fn		= throtl_pd_offline,
 	.pd_free_fn		= throtl_pd_free,
 };
 
@@ -1595,6 +1672,7 @@  int blk_throtl_init(struct request_queue *q)
 	td->queue = q;
 
 	td->limit_valid[LIMIT_MAX] = true;
+	td->limit_index = LIMIT_MAX;
 	/* activate policy */
 	ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
 	if (ret)