| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20200901185257.645114-21-tj@kernel.org>
Date: Tue, 1 Sep 2020 14:52:50 -0400
From: Tejun Heo <tj@...nel.org>
To: axboe@...nel.dk
Cc: linux-block@...r.kernel.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-team@...com, newella@...com,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 20/27] blk-iocost: revamp in-period donation snapbacks
When the margin drops below the minimum on a donating iocg, donation is
immediately canceled in full. There are a couple shortcomings with the
current behavior.
* It's abrupt. A small temporary budget deficit can lead to a wide swing in
weight allocation and a large surplus.
* It's open coded in the issue path but not implemented for the merge path.
A series of merges at a low inuse can make the iocg incur debts and stall
incorrectly.
This patch reimplements in-period donation snapbacks so that
* inuse adjustment and cost calculations are factored into
adjust_inuse_and_calc_cost() which is called from both the issue and merge
paths.
* Snapbacks are more gradual. It occurs in quarter steps.
* A snapback triggers if the margin goes below the low threshold and is
lower than the budget at the time of the last adjustment.
* For the above, __propagate_weights() stores the margin in
iocg->saved_margin. Move iocg->last_inuse storing together into
__propagate_weights() for consistency.
* Full snapback is guaranteed when there are waiters.
* With precise donation and gradual snapbacks, inuse adjustments are now a
lot more effective and the value of scaling inuse on weight changes isn't
clear. Removed inuse scaling from weight_update().
Signed-off-by: Tejun Heo <tj@...nel.org>
---
block/blk-iocost.c | 133 ++++++++++++++++++++++++++++++++-------------
1 file changed, 96 insertions(+), 37 deletions(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 694f1487208a..d09b4011449c 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -226,6 +226,8 @@ enum {
MARGIN_TARGET_PCT = 50,
MARGIN_MAX_PCT = 100,
+ INUSE_ADJ_STEP_PCT = 25,
+
/* Have some play in timer operations */
TIMER_SLACK_PCT = 1,
@@ -443,12 +445,17 @@ struct ioc_gq {
*
* `last_inuse` remembers `inuse` while an iocg is idle to persist
* surplus adjustments.
+ *
+ * `inuse` may be adjusted dynamically during period. `saved_*` are used
+ * to determine and track adjustments.
*/
u32 cfg_weight;
u32 weight;
u32 active;
u32 inuse;
+
u32 last_inuse;
+ s64 saved_margin;
sector_t cursor; /* to detect randio */
@@ -934,9 +941,11 @@ static void ioc_start_period(struct ioc *ioc, struct ioc_now *now)
/*
* Update @iocg's `active` and `inuse` to @active and @inuse, update level
- * weight sums and propagate upwards accordingly.
+ * weight sums and propagate upwards accordingly. If @save, the current margin
+ * is saved to be used as reference for later inuse in-period adjustments.
*/
-static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse)
+static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
+ bool save, struct ioc_now *now)
{
struct ioc *ioc = iocg->ioc;
int lvl;
@@ -945,6 +954,10 @@ static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse)
inuse = clamp_t(u32, inuse, 1, active);
+ iocg->last_inuse = iocg->inuse;
+ if (save)
+ iocg->saved_margin = now->vnow - atomic64_read(&iocg->vtime);
+
if (active == iocg->active && inuse == iocg->inuse)
return;
@@ -996,9 +1009,10 @@ static void commit_weights(struct ioc *ioc)
}
}
-static void propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse)
+static void propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
+ bool save, struct ioc_now *now)
{
- __propagate_weights(iocg, active, inuse);
+ __propagate_weights(iocg, active, inuse, save, now);
commit_weights(iocg->ioc);
}
@@ -1082,7 +1096,7 @@ static u32 current_hweight_max(struct ioc_gq *iocg)
return max_t(u32, hwm, 1);
}
-static void weight_updated(struct ioc_gq *iocg)
+static void weight_updated(struct ioc_gq *iocg, struct ioc_now *now)
{
struct ioc *ioc = iocg->ioc;
struct blkcg_gq *blkg = iocg_to_blkg(iocg);
@@ -1093,9 +1107,7 @@ static void weight_updated(struct ioc_gq *iocg)
weight = iocg->cfg_weight ?: iocc->dfl_weight;
if (weight != iocg->weight && iocg->active)
- propagate_weights(iocg, weight,
- DIV64_U64_ROUND_UP((u64)iocg->inuse * weight,
- iocg->weight));
+ propagate_weights(iocg, weight, iocg->inuse, true, now);
iocg->weight = weight;
}
@@ -1165,8 +1177,9 @@ static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now)
*/
iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1;
list_add(&iocg->active_list, &ioc->active_iocgs);
+
propagate_weights(iocg, iocg->weight,
- iocg->last_inuse ?: iocg->weight);
+ iocg->last_inuse ?: iocg->weight, true, now);
TRACE_IOCG_PATH(iocg_activate, iocg, now,
last_period, cur_period, vtime);
@@ -1789,7 +1802,7 @@ static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now)
inuse = DIV64_U64_ROUND_UP(
parent->child_adjusted_sum * iocg->hweight_after_donation,
parent->hweight_inuse);
- __propagate_weights(iocg, iocg->active, inuse);
+ __propagate_weights(iocg, iocg->active, inuse, true, now);
}
/* walk list should be dissolved after use */
@@ -1844,8 +1857,7 @@ static void ioc_timer_fn(struct timer_list *timer)
iocg_kick_waitq(iocg, true, &now);
} else if (iocg_is_idle(iocg)) {
/* no waiter and idle, deactivate */
- iocg->last_inuse = iocg->inuse;
- __propagate_weights(iocg, 0, 0);
+ __propagate_weights(iocg, 0, 0, false, &now);
list_del_init(&iocg->active_list);
}
@@ -1925,7 +1937,7 @@ static void ioc_timer_fn(struct timer_list *timer)
list_add(&iocg->surplus_list, &surpluses);
} else {
__propagate_weights(iocg, iocg->active,
- iocg->active);
+ iocg->active, true, &now);
nr_shortages++;
}
} else {
@@ -2055,6 +2067,50 @@ static void ioc_timer_fn(struct timer_list *timer)
spin_unlock_irq(&ioc->lock);
}
+static u64 adjust_inuse_and_calc_cost(struct ioc_gq *iocg, u64 vtime,
+ u64 abs_cost, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct ioc_margins *margins = &ioc->margins;
+ u32 adj_step = DIV_ROUND_UP(iocg->active * INUSE_ADJ_STEP_PCT, 100);
+ u32 hwi;
+ s64 margin;
+ u64 cost, new_inuse;
+
+ current_hweight(iocg, NULL, &hwi);
+ cost = abs_cost_to_cost(abs_cost, hwi);
+ margin = now->vnow - vtime - cost;
+
+ /*
+ * We only increase inuse during period and do so iff the margin has
+ * deteriorated since the previous adjustment.
+ */
+ if (margin >= iocg->saved_margin || margin >= margins->low ||
+ iocg->inuse == iocg->active)
+ return cost;
+
+ spin_lock_irq(&ioc->lock);
+
+ /* we own inuse only when @iocg is in the normal active state */
+ if (list_empty(&iocg->active_list)) {
+ spin_unlock_irq(&ioc->lock);
+ return cost;
+ }
+
+ /* bump up inuse till @abs_cost fits in the existing budget */
+ new_inuse = iocg->inuse;
+ do {
+ new_inuse = new_inuse + adj_step;
+ propagate_weights(iocg, iocg->active, new_inuse, true, now);
+ current_hweight(iocg, NULL, &hwi);
+ cost = abs_cost_to_cost(abs_cost, hwi);
+ } while (time_after64(vtime + cost, now->vnow) &&
+ iocg->inuse != iocg->active);
+
+ spin_unlock_irq(&ioc->lock);
+ return cost;
+}
+
static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
bool is_merge, u64 *costp)
{
@@ -2136,7 +2192,6 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
struct ioc_gq *iocg = blkg_to_iocg(blkg);
struct ioc_now now;
struct iocg_wait wait;
- u32 hw_active, hw_inuse;
u64 abs_cost, cost, vtime;
bool use_debt, ioc_locked;
unsigned long flags;
@@ -2154,21 +2209,8 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
return;
iocg->cursor = bio_end_sector(bio);
-
vtime = atomic64_read(&iocg->vtime);
- current_hweight(iocg, &hw_active, &hw_inuse);
-
- if (hw_inuse < hw_active &&
- time_after_eq64(vtime + ioc->margins.min, now.vnow)) {
- TRACE_IOCG_PATH(inuse_reset, iocg, &now,
- iocg->inuse, iocg->weight, hw_inuse, hw_active);
- spin_lock_irq(&ioc->lock);
- propagate_weights(iocg, iocg->weight, iocg->weight);
- spin_unlock_irq(&ioc->lock);
- current_hweight(iocg, &hw_active, &hw_inuse);
- }
-
- cost = abs_cost_to_cost(abs_cost, hw_inuse);
+ cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
/*
* If no one's waiting and within budget, issue right away. The
@@ -2190,7 +2232,7 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
*/
use_debt = bio_issue_as_root_blkg(bio) || fatal_signal_pending(current);
ioc_locked = use_debt || READ_ONCE(iocg->abs_vdebt);
-
+retry_lock:
iocg_lock(iocg, ioc_locked, &flags);
/*
@@ -2232,6 +2274,17 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
return;
}
+ /* guarantee that iocgs w/ waiters have maximum inuse */
+ if (iocg->inuse != iocg->active) {
+ if (!ioc_locked) {
+ iocg_unlock(iocg, false, &flags);
+ ioc_locked = true;
+ goto retry_lock;
+ }
+ propagate_weights(iocg, iocg->active, iocg->active, true,
+ &now);
+ }
+
/*
* Append self to the waitq and schedule the wakeup timer if we're
* the first waiter. The timer duration is calculated based on the
@@ -2274,8 +2327,7 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
struct ioc *ioc = iocg->ioc;
sector_t bio_end = bio_end_sector(bio);
struct ioc_now now;
- u32 hw_inuse;
- u64 abs_cost, cost;
+ u64 vtime, abs_cost, cost;
unsigned long flags;
/* bypass if disabled or for root cgroup */
@@ -2287,8 +2339,9 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
return;
ioc_now(ioc, &now);
- current_hweight(iocg, NULL, &hw_inuse);
- cost = abs_cost_to_cost(abs_cost, hw_inuse);
+
+ vtime = atomic64_read(&iocg->vtime);
+ cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
/* update cursor if backmerging into the request at the cursor */
if (blk_rq_pos(rq) < bio_end &&
@@ -2530,7 +2583,7 @@ static void ioc_pd_init(struct blkg_policy_data *pd)
}
spin_lock_irqsave(&ioc->lock, flags);
- weight_updated(iocg);
+ weight_updated(iocg, &now);
spin_unlock_irqrestore(&ioc->lock, flags);
}
@@ -2544,7 +2597,10 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
spin_lock_irqsave(&ioc->lock, flags);
if (!list_empty(&iocg->active_list)) {
- propagate_weights(iocg, 0, 0);
+ struct ioc_now now;
+
+ ioc_now(ioc, &now);
+ propagate_weights(iocg, 0, 0, false, &now);
list_del_init(&iocg->active_list);
}
@@ -2612,6 +2668,7 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
struct blkcg *blkcg = css_to_blkcg(of_css(of));
struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
struct blkg_conf_ctx ctx;
+ struct ioc_now now;
struct ioc_gq *iocg;
u32 v;
int ret;
@@ -2632,7 +2689,8 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
if (iocg) {
spin_lock_irq(&iocg->ioc->lock);
- weight_updated(iocg);
+ ioc_now(iocg->ioc, &now);
+ weight_updated(iocg, &now);
spin_unlock_irq(&iocg->ioc->lock);
}
}
@@ -2658,7 +2716,8 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
spin_lock(&iocg->ioc->lock);
iocg->cfg_weight = v * WEIGHT_ONE;
- weight_updated(iocg);
+ ioc_now(iocg->ioc, &now);
+ weight_updated(iocg, &now);
spin_unlock(&iocg->ioc->lock);
blkg_conf_finish(&ctx);
--
2.26.2
Powered by blists - more mailing lists