| 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: <20240304201625.100619-3-christian.loehle@arm.com>
Date: Mon, 4 Mar 2024 20:16:25 +0000
From: Christian Loehle <christian.loehle@....com>
To: linux-kernel@...r.kernel.org
Cc: peterz@...radead.org,
juri.lelli@...hat.com,
mingo@...hat.com,
rafael@...nel.org,
dietmar.eggemann@....com,
vschneid@...hat.com,
vincent.guittot@...aro.org,
Johannes.Thumshirn@....com,
adrian.hunter@...el.com,
ulf.hansson@...aro.org,
andres@...razel.de,
asml.silence@...il.com,
linux-pm@...r.kernel.org,
linux-block@...r.kernel.org,
io-uring@...r.kernel.org,
Christian Loehle <christian.loehle@....com>
Subject: [RFC PATCH 2/2] cpufreq/schedutil: Remove iowait boost
The previous commit provides a new cpu_util_cfs_boost_io interface for
schedutil which uses the io boosted utilization of the per-task
tracking strategy. Schedutil iowait boosting is therefore no longer
necessary so remove it.
Signed-off-by: Christian Loehle <christian.loehle@....com>
---
kernel/sched/cpufreq_schedutil.c | 152 +------------------------------
1 file changed, 5 insertions(+), 147 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index cd0ca3cbd212..ed9fc88a74fc 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -6,8 +6,6 @@
* Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
*/
-#define IOWAIT_BOOST_MIN (SCHED_CAPACITY_SCALE / 8)
-
struct sugov_tunables {
struct gov_attr_set attr_set;
unsigned int rate_limit_us;
@@ -42,10 +40,6 @@ struct sugov_cpu {
struct sugov_policy *sg_policy;
unsigned int cpu;
- bool iowait_boost_pending;
- unsigned int iowait_boost;
- u64 last_update;
-
unsigned long util;
unsigned long bw_min;
@@ -195,141 +189,17 @@ unsigned long sugov_effective_cpu_perf(int cpu, unsigned long actual,
return max(min, max);
}
-static void sugov_get_util(struct sugov_cpu *sg_cpu, unsigned long boost)
+static void sugov_get_util(struct sugov_cpu *sg_cpu)
{
unsigned long min, max, util = cpu_util_cfs_boost(sg_cpu->cpu);
unsigned long io_boost = cpu_util_io_boost(sg_cpu->cpu);
- /*
- * XXX: This already includes io boost now, makes little sense with
- * sugov iowait boost on top
- */
util = max(util, io_boost);
util = effective_cpu_util(sg_cpu->cpu, util, &min, &max);
- util = max(util, boost);
sg_cpu->bw_min = min;
sg_cpu->util = sugov_effective_cpu_perf(sg_cpu->cpu, util, min, max);
}
-/**
- * sugov_iowait_reset() - Reset the IO boost status of a CPU.
- * @sg_cpu: the sugov data for the CPU to boost
- * @time: the update time from the caller
- * @set_iowait_boost: true if an IO boost has been requested
- *
- * The IO wait boost of a task is disabled after a tick since the last update
- * of a CPU. If a new IO wait boost is requested after more then a tick, then
- * we enable the boost starting from IOWAIT_BOOST_MIN, which improves energy
- * efficiency by ignoring sporadic wakeups from IO.
- */
-static bool sugov_iowait_reset(struct sugov_cpu *sg_cpu, u64 time,
- bool set_iowait_boost)
-{
- s64 delta_ns = time - sg_cpu->last_update;
-
- /* Reset boost only if a tick has elapsed since last request */
- if (delta_ns <= TICK_NSEC)
- return false;
-
- sg_cpu->iowait_boost = set_iowait_boost ? IOWAIT_BOOST_MIN : 0;
- sg_cpu->iowait_boost_pending = set_iowait_boost;
-
- return true;
-}
-
-/**
- * sugov_iowait_boost() - Updates the IO boost status of a CPU.
- * @sg_cpu: the sugov data for the CPU to boost
- * @time: the update time from the caller
- * @flags: SCHED_CPUFREQ_IOWAIT if the task is waking up after an IO wait
- *
- * Each time a task wakes up after an IO operation, the CPU utilization can be
- * boosted to a certain utilization which doubles at each "frequent and
- * successive" wakeup from IO, ranging from IOWAIT_BOOST_MIN to the utilization
- * of the maximum OPP.
- *
- * To keep doubling, an IO boost has to be requested at least once per tick,
- * otherwise we restart from the utilization of the minimum OPP.
- */
-static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
- unsigned int flags)
-{
- bool set_iowait_boost = flags & SCHED_CPUFREQ_IOWAIT;
-
- /* Reset boost if the CPU appears to have been idle enough */
- if (sg_cpu->iowait_boost &&
- sugov_iowait_reset(sg_cpu, time, set_iowait_boost))
- return;
-
- /* Boost only tasks waking up after IO */
- if (!set_iowait_boost)
- return;
-
- /* Ensure boost doubles only one time at each request */
- if (sg_cpu->iowait_boost_pending)
- return;
- sg_cpu->iowait_boost_pending = true;
-
- /* Double the boost at each request */
- if (sg_cpu->iowait_boost) {
- sg_cpu->iowait_boost =
- min_t(unsigned int, sg_cpu->iowait_boost << 1, SCHED_CAPACITY_SCALE);
- return;
- }
-
- /* First wakeup after IO: start with minimum boost */
- sg_cpu->iowait_boost = IOWAIT_BOOST_MIN;
-}
-
-/**
- * sugov_iowait_apply() - Apply the IO boost to a CPU.
- * @sg_cpu: the sugov data for the cpu to boost
- * @time: the update time from the caller
- * @max_cap: the max CPU capacity
- *
- * A CPU running a task which woken up after an IO operation can have its
- * utilization boosted to speed up the completion of those IO operations.
- * The IO boost value is increased each time a task wakes up from IO, in
- * sugov_iowait_apply(), and it's instead decreased by this function,
- * each time an increase has not been requested (!iowait_boost_pending).
- *
- * A CPU which also appears to have been idle for at least one tick has also
- * its IO boost utilization reset.
- *
- * This mechanism is designed to boost high frequently IO waiting tasks, while
- * being more conservative on tasks which does sporadic IO operations.
- */
-static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
- unsigned long max_cap)
-{
- /* No boost currently required */
- if (!sg_cpu->iowait_boost)
- return 0;
-
- /* Reset boost if the CPU appears to have been idle enough */
- if (sugov_iowait_reset(sg_cpu, time, false))
- return 0;
-
- if (!sg_cpu->iowait_boost_pending) {
- /*
- * No boost pending; reduce the boost value.
- */
- sg_cpu->iowait_boost >>= 1;
- if (sg_cpu->iowait_boost < IOWAIT_BOOST_MIN) {
- sg_cpu->iowait_boost = 0;
- return 0;
- }
- }
-
- sg_cpu->iowait_boost_pending = false;
-
- /*
- * sg_cpu->util is already in capacity scale; convert iowait_boost
- * into the same scale so we can compare.
- */
- return (sg_cpu->iowait_boost * max_cap) >> SCHED_CAPACITY_SHIFT;
-}
-
#ifdef CONFIG_NO_HZ_COMMON
static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
{
@@ -357,18 +227,12 @@ static inline bool sugov_update_single_common(struct sugov_cpu *sg_cpu,
u64 time, unsigned long max_cap,
unsigned int flags)
{
- unsigned long boost;
-
- sugov_iowait_boost(sg_cpu, time, flags);
- sg_cpu->last_update = time;
-
ignore_dl_rate_limit(sg_cpu);
if (!sugov_should_update_freq(sg_cpu->sg_policy, time))
return false;
- boost = sugov_iowait_apply(sg_cpu, time, max_cap);
- sugov_get_util(sg_cpu, boost);
+ sugov_get_util(sg_cpu);
return true;
}
@@ -458,7 +322,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
sg_cpu->sg_policy->last_freq_update_time = time;
}
-static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
+static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu)
{
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
struct cpufreq_policy *policy = sg_policy->policy;
@@ -469,11 +333,8 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
for_each_cpu(j, policy->cpus) {
struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
- unsigned long boost;
-
- boost = sugov_iowait_apply(j_sg_cpu, time, max_cap);
- sugov_get_util(j_sg_cpu, boost);
+ sugov_get_util(j_sg_cpu);
util = max(j_sg_cpu->util, util);
}
@@ -489,13 +350,10 @@ sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags)
raw_spin_lock(&sg_policy->update_lock);
- sugov_iowait_boost(sg_cpu, time, flags);
- sg_cpu->last_update = time;
-
ignore_dl_rate_limit(sg_cpu);
if (sugov_should_update_freq(sg_policy, time)) {
- next_f = sugov_next_freq_shared(sg_cpu, time);
+ next_f = sugov_next_freq_shared(sg_cpu);
if (!sugov_update_next_freq(sg_policy, time, next_f))
goto unlock;
--
2.34.1
Powered by blists - more mailing lists