path: root/SOURCES/cachy-bore.patch

From 61efc6f62710e42ca623e209f901394d4f356cc9 Mon Sep 17 00:00:00 2001
From: Peter Jung <admin@ptr1337.dev>
Date: Thu, 30 May 2024 10:45:04 +0200
Subject: [PATCH] bore

Signed-off-by: Peter Jung <admin@ptr1337.dev>
---
 include/linux/sched.h   |  10 ++
 init/Kconfig            |  17 +++
 kernel/sched/core.c     | 143 +++++++++++++++++++++
 kernel/sched/debug.c    |  60 ++++++++-
 kernel/sched/fair.c     | 272 +++++++++++++++++++++++++++++++++++++---
 kernel/sched/features.h |  20 ++-
 kernel/sched/sched.h    |   7 ++
 7 files changed, 512 insertions(+), 17 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3c2abbc587b49..e7bf3a034aa20 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -547,6 +547,16 @@ struct sched_entity {
 	u64				sum_exec_runtime;
 	u64				prev_sum_exec_runtime;
 	u64				vruntime;
+#ifdef CONFIG_SCHED_BORE
+	u64				burst_time;
+	u8				prev_burst_penalty;
+	u8				curr_burst_penalty;
+	u8				burst_penalty;
+	u8				burst_score;
+	u8				child_burst;
+	u32				child_burst_cnt;
+	u64				child_burst_last_cached;
+#endif // CONFIG_SCHED_BORE
 	s64				vlag;
 	u64				slice;
 
diff --git a/init/Kconfig b/init/Kconfig
index 664bedb9a71fb..6f9c7fc90707a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1279,6 +1279,23 @@ config CHECKPOINT_RESTORE
 
 	  If unsure, say N here.
 
+config SCHED_BORE
+	bool "Burst-Oriented Response Enhancer"
+	default y
+	help
+	  In Desktop and Mobile computing, one might prefer interactive
+	  tasks to keep responsive no matter what they run in the background.
+
+	  Enabling this kernel feature modifies the scheduler to discriminate
+	  tasks by their burst time (runtime since it last went sleeping or
+	  yielding state) and prioritize those that run less bursty.
+	  Such tasks usually include window compositor, widgets backend,
+	  terminal emulator, video playback, games and so on.
+	  With a little impact to scheduling fairness, it may improve
+	  responsiveness especially under heavy background workload.
+
+	  If unsure, say Y here.
+
 config SCHED_AUTOGROUP
 	bool "Automatic process group scheduling"
 	select CGROUPS
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d211d40a2edc9..362df741dc85e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4516,6 +4516,138 @@ int wake_up_state(struct task_struct *p, unsigned int state)
 	return try_to_wake_up(p, state, 0);
 }
 
+#ifdef CONFIG_SCHED_BORE
+extern u8   sched_burst_fork_atavistic;
+extern uint sched_burst_cache_lifetime;
+
+static void __init sched_init_bore(void) {
+	init_task.se.burst_time = 0;
+	init_task.se.prev_burst_penalty = 0;
+	init_task.se.curr_burst_penalty = 0;
+	init_task.se.burst_penalty = 0;
+	init_task.se.burst_score = 0;
+	init_task.se.child_burst_last_cached = 0;
+}
+
+void inline sched_fork_bore(struct task_struct *p) {
+	p->se.burst_time = 0;
+	p->se.curr_burst_penalty = 0;
+	p->se.burst_score = 0;
+	p->se.child_burst_last_cached = 0;
+}
+
+static u32 count_child_tasks(struct task_struct *p) {
+	struct task_struct *child;
+	u32 cnt = 0;
+	list_for_each_entry(child, &p->children, sibling) {cnt++;}
+	return cnt;
+}
+
+static inline bool task_is_inheritable(struct task_struct *p) {
+	return (p->sched_class == &fair_sched_class);
+}
+
+static inline bool child_burst_cache_expired(struct task_struct *p, u64 now) {
+	u64 expiration_time =
+		p->se.child_burst_last_cached + sched_burst_cache_lifetime;
+	return ((s64)(expiration_time - now) < 0);
+}
+
+static void __update_child_burst_cache(
+	struct task_struct *p, u32 cnt, u32 sum, u64 now) {
+	u8 avg = 0;
+	if (cnt) avg = sum / cnt;
+	p->se.child_burst = max(avg, p->se.burst_penalty);
+	p->se.child_burst_cnt = cnt;
+	p->se.child_burst_last_cached = now;
+}
+
+static inline void update_child_burst_direct(struct task_struct *p, u64 now) {
+	struct task_struct *child;
+	u32 cnt = 0;
+	u32 sum = 0;
+
+	list_for_each_entry(child, &p->children, sibling) {
+		if (!task_is_inheritable(child)) continue;
+		cnt++;
+		sum += child->se.burst_penalty;
+	}
+
+	__update_child_burst_cache(p, cnt, sum, now);
+}
+
+static inline u8 __inherit_burst_direct(struct task_struct *p, u64 now) {
+	struct task_struct *parent = p->real_parent;
+	if (child_burst_cache_expired(parent, now))
+		update_child_burst_direct(parent, now);
+
+	return parent->se.child_burst;
+}
+
+static void update_child_burst_topological(
+	struct task_struct *p, u64 now, u32 depth, u32 *acnt, u32 *asum) {
+	struct task_struct *child, *dec;
+	u32 cnt = 0, dcnt = 0;
+	u32 sum = 0;
+
+	list_for_each_entry(child, &p->children, sibling) {
+		dec = child;
+		while ((dcnt = count_child_tasks(dec)) == 1)
+			dec = list_first_entry(&dec->children, struct task_struct, sibling);
+		
+		if (!dcnt || !depth) {
+			if (!task_is_inheritable(dec)) continue;
+			cnt++;
+			sum += dec->se.burst_penalty;
+			continue;
+		}
+		if (!child_burst_cache_expired(dec, now)) {
+			cnt += dec->se.child_burst_cnt;
+			sum += (u32)dec->se.child_burst * dec->se.child_burst_cnt;
+			continue;
+		}
+		update_child_burst_topological(dec, now, depth - 1, &cnt, &sum);
+	}
+
+	__update_child_burst_cache(p, cnt, sum, now);
+	*acnt += cnt;
+	*asum += sum;
+}
+
+static inline u8 __inherit_burst_topological(struct task_struct *p, u64 now) {
+	struct task_struct *anc = p->real_parent;
+	u32 cnt = 0, sum = 0;
+
+	while (anc->real_parent != anc && count_child_tasks(anc) == 1)
+		anc = anc->real_parent;
+
+	if (child_burst_cache_expired(anc, now))
+		update_child_burst_topological(
+			anc, now, sched_burst_fork_atavistic - 1, &cnt, &sum);
+
+	return anc->se.child_burst;
+}
+
+static inline void inherit_burst(struct task_struct *p) {
+	u8 burst_cache;
+	u64 now = ktime_get_ns();
+
+	read_lock(&tasklist_lock);
+	burst_cache = likely(sched_burst_fork_atavistic)?
+		__inherit_burst_topological(p, now):
+		__inherit_burst_direct(p, now);
+	read_unlock(&tasklist_lock);
+
+	p->se.prev_burst_penalty = max(p->se.prev_burst_penalty, burst_cache);
+}
+
+static void sched_post_fork_bore(struct task_struct *p) {
+	if (p->sched_class == &fair_sched_class)
+		inherit_burst(p);
+	p->se.burst_penalty = p->se.prev_burst_penalty;
+}
+#endif // CONFIG_SCHED_BORE
+
 /*
  * Perform scheduler related setup for a newly forked process p.
  * p is forked by current.
@@ -4532,6 +4664,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	p->se.prev_sum_exec_runtime	= 0;
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
+#ifdef CONFIG_SCHED_BORE
+	sched_fork_bore(p);
+#endif // CONFIG_SCHED_BORE
 	p->se.vlag			= 0;
 	p->se.slice			= sysctl_sched_base_slice;
 	INIT_LIST_HEAD(&p->se.group_node);
@@ -4848,6 +4983,9 @@ void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)
 
 void sched_post_fork(struct task_struct *p)
 {
+#ifdef CONFIG_SCHED_BORE
+	sched_post_fork_bore(p);
+#endif // CONFIG_SCHED_BORE
 	uclamp_post_fork(p);
 }
 
@@ -9931,6 +10069,11 @@ void __init sched_init(void)
 	BUG_ON(&dl_sched_class != &stop_sched_class + 1);
 #endif
 
+#ifdef CONFIG_SCHED_BORE
+	sched_init_bore();
+	printk(KERN_INFO "BORE (Burst-Oriented Response Enhancer) CPU Scheduler modification 5.2.0 by Masahito Suzuki");
+#endif // CONFIG_SCHED_BORE
+
 	wait_bit_init();
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 8d5d98a5834df..b1786126171e9 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -167,7 +167,52 @@ static const struct file_operations sched_feat_fops = {
 };
 
 #ifdef CONFIG_SMP
+#ifdef CONFIG_SCHED_BORE
+static ssize_t sched_min_base_slice_write(struct file *filp, const char __user *ubuf,
+				   size_t cnt, loff_t *ppos)
+{
+	char buf[16];
+	unsigned int value;
+
+	if (cnt > 15)
+		cnt = 15;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+	buf[cnt] = '\0';
+
+	if (kstrtouint(buf, 10, &value))
+		return -EINVAL;
 
+	if (!value)
+		return -EINVAL;
+
+	sysctl_sched_min_base_slice = value;
+	sched_update_min_base_slice();
+
+	*ppos += cnt;
+	return cnt;
+}
+
+static int sched_min_base_slice_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%d\n", sysctl_sched_min_base_slice);
+	return 0;
+}
+
+static int sched_min_base_slice_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, sched_min_base_slice_show, NULL);
+}
+
+static const struct file_operations sched_min_base_slice_fops = {
+	.open		= sched_min_base_slice_open,
+	.write		= sched_min_base_slice_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+#else // !CONFIG_SCHED_BORE
 static ssize_t sched_scaling_write(struct file *filp, const char __user *ubuf,
 				   size_t cnt, loff_t *ppos)
 {
@@ -213,7 +258,7 @@ static const struct file_operations sched_scaling_fops = {
 	.llseek		= seq_lseek,
 	.release	= single_release,
 };
-
+#endif // CONFIG_SCHED_BORE
 #endif /* SMP */
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
@@ -347,13 +392,20 @@ static __init int sched_init_debug(void)
 	debugfs_create_file("preempt", 0644, debugfs_sched, NULL, &sched_dynamic_fops);
 #endif
 
+#ifdef CONFIG_SCHED_BORE
+	debugfs_create_file("min_base_slice_ns", 0644, debugfs_sched, NULL, &sched_min_base_slice_fops);
+	debugfs_create_u32("base_slice_ns", 0400, debugfs_sched, &sysctl_sched_base_slice);
+#else // !CONFIG_SCHED_BORE
 	debugfs_create_u32("base_slice_ns", 0644, debugfs_sched, &sysctl_sched_base_slice);
+#endif // CONFIG_SCHED_BORE
 
 	debugfs_create_u32("latency_warn_ms", 0644, debugfs_sched, &sysctl_resched_latency_warn_ms);
 	debugfs_create_u32("latency_warn_once", 0644, debugfs_sched, &sysctl_resched_latency_warn_once);
 
 #ifdef CONFIG_SMP
+#if !defined(CONFIG_SCHED_BORE)
 	debugfs_create_file("tunable_scaling", 0644, debugfs_sched, NULL, &sched_scaling_fops);
+#endif // CONFIG_SCHED_BORE
 	debugfs_create_u32("migration_cost_ns", 0644, debugfs_sched, &sysctl_sched_migration_cost);
 	debugfs_create_u32("nr_migrate", 0644, debugfs_sched, &sysctl_sched_nr_migrate);
 
@@ -595,6 +647,9 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
 		SPLIT_NS(schedstat_val_or_zero(p->stats.sum_sleep_runtime)),
 		SPLIT_NS(schedstat_val_or_zero(p->stats.sum_block_runtime)));
 
+#ifdef CONFIG_SCHED_BORE
+	SEQ_printf(m, " %2d", p->se.burst_score);
+#endif // CONFIG_SCHED_BORE
 #ifdef CONFIG_NUMA_BALANCING
 	SEQ_printf(m, " %d %d", task_node(p), task_numa_group_id(p));
 #endif
@@ -1068,6 +1123,9 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
 
 	P(se.load.weight);
 #ifdef CONFIG_SMP
+#ifdef CONFIG_SCHED_BORE
+	P(se.burst_score);
+#endif // CONFIG_SCHED_BORE
 	P(se.avg.load_sum);
 	P(se.avg.runnable_sum);
 	P(se.avg.util_sum);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 213c94d027a4c..3c2d149d0235d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -19,6 +19,9 @@
  *
  *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
+ *
+ *  Burst-Oriented Response Enhancer (BORE) CPU Scheduler
+ *  Copyright (C) 2021-2024 Masahito Suzuki <firelzrd@gmail.com>
  */
 #include <linux/energy_model.h>
 #include <linux/mmap_lock.h>
@@ -64,20 +67,125 @@
  *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
  *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
  *
- * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
+ * (BORE  default SCHED_TUNABLESCALING_NONE = *1 constant)
+ * (EEVDF default SCHED_TUNABLESCALING_LOG  = *(1+ilog(ncpus))
  */
+#ifdef CONFIG_SCHED_BORE
+unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_NONE;
+#else // !CONFIG_SCHED_BORE
 unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
+#endif // CONFIG_SCHED_BORE
 
 /*
  * Minimal preemption granularity for CPU-bound tasks:
  *
- * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
+ * (BORE  default: max(1 sec / HZ, min_base_slice) constant, units: nanoseconds)
+ * (EEVDF default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
+#ifdef CONFIG_SCHED_BORE
+unsigned int            sysctl_sched_base_slice = 1000000000ULL / HZ;
+static unsigned int configured_sched_base_slice = 1000000000ULL / HZ;
+unsigned int        sysctl_sched_min_base_slice =    2000000ULL;
+#else // !CONFIG_SCHED_BORE
 unsigned int sysctl_sched_base_slice			= 750000ULL;
 static unsigned int normalized_sysctl_sched_base_slice	= 750000ULL;
+#endif // CONFIG_SCHED_BORE
 
 const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
 
+#ifdef CONFIG_SCHED_BORE
+u8   __read_mostly sched_bore                   = 1;
+u8   __read_mostly sched_burst_smoothness_long  = 1;
+u8   __read_mostly sched_burst_smoothness_short = 0;
+u8   __read_mostly sched_burst_fork_atavistic   = 2;
+u8   __read_mostly sched_burst_penalty_offset   = 22;
+uint __read_mostly sched_burst_penalty_scale    = 1280;
+uint __read_mostly sched_burst_cache_lifetime   = 60000000;
+static int __maybe_unused sixty_four     = 64;
+static int __maybe_unused maxval_12_bits = 4095;
+
+#define MAX_BURST_PENALTY (39U <<2)
+
+static inline u32 log2plus1_u64_u32f8(u64 v) {
+	u32 msb = fls64(v);
+	s32 excess_bits = msb - 9;
+    u8 fractional = (0 <= excess_bits)? v >> excess_bits: v << -excess_bits;
+	return msb << 8 | fractional;
+}
+
+static inline u32 calc_burst_penalty(u64 burst_time) {
+	u32 greed, tolerance, penalty, scaled_penalty;
+	
+	greed = log2plus1_u64_u32f8(burst_time);
+	tolerance = sched_burst_penalty_offset << 8;
+	penalty = max(0, (s32)greed - (s32)tolerance);
+	scaled_penalty = penalty * sched_burst_penalty_scale >> 16;
+
+	return min(MAX_BURST_PENALTY, scaled_penalty);
+}
+
+static inline u64 scale_slice(u64 delta, struct sched_entity *se) {
+	return mul_u64_u32_shr(delta, sched_prio_to_wmult[se->burst_score], 22);
+}
+
+static inline u64 __unscale_slice(u64 delta, u8 score) {
+	return mul_u64_u32_shr(delta, sched_prio_to_weight[score], 10);
+}
+
+static inline u64 unscale_slice(u64 delta, struct sched_entity *se) {
+	return __unscale_slice(delta, se->burst_score);
+}
+
+void reweight_task(struct task_struct *p, int prio);
+
+static void update_burst_score(struct sched_entity *se) {
+	if (!entity_is_task(se)) return;
+	struct task_struct *p = task_of(se);
+	u8 prio = p->static_prio - MAX_RT_PRIO;
+	u8 prev_prio = min(39, prio + se->burst_score);
+
+	se->burst_score = se->burst_penalty >> 2;
+
+	u8 new_prio = min(39, prio + se->burst_score);
+	if (new_prio != prev_prio)
+		reweight_task(p, new_prio);
+}
+
+static void update_burst_penalty(struct sched_entity *se) {
+	se->curr_burst_penalty = calc_burst_penalty(se->burst_time);
+	se->burst_penalty = max(se->prev_burst_penalty, se->curr_burst_penalty);
+	update_burst_score(se);
+}
+
+static inline u32 binary_smooth(u32 new, u32 old) {
+  int increment = new - old;
+  return (0 <= increment)?
+    old + ( increment >> (int)sched_burst_smoothness_long):
+    old - (-increment >> (int)sched_burst_smoothness_short);
+}
+
+static void restart_burst(struct sched_entity *se) {
+	se->burst_penalty = se->prev_burst_penalty =
+		binary_smooth(se->curr_burst_penalty, se->prev_burst_penalty);
+	se->curr_burst_penalty = 0;
+	se->burst_time = 0;
+	update_burst_score(se);
+}
+
+static void restart_burst_rescale_deadline(struct sched_entity *se) {
+	s64 vscaled, wremain, vremain = se->deadline - se->vruntime;
+	u8 prev_score = se->burst_score;
+	restart_burst(se);
+	if (prev_score > se->burst_score) {
+		wremain = __unscale_slice(abs(vremain), prev_score);
+		vscaled = scale_slice(wremain, se);
+		if (unlikely(vremain < 0))
+			vscaled = -vscaled;
+		se->deadline = se->vruntime + vscaled;
+	}
+}
+#endif // CONFIG_SCHED_BORE
+
 int sched_thermal_decay_shift;
 static int __init setup_sched_thermal_decay_shift(char *str)
 {
@@ -137,6 +245,69 @@ static unsigned int sysctl_numa_balancing_promote_rate_limit = 65536;
 
 #ifdef CONFIG_SYSCTL
 static struct ctl_table sched_fair_sysctls[] = {
+#ifdef CONFIG_SCHED_BORE
+	{
+		.procname	= "sched_bore",
+		.data		= &sched_bore,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "sched_burst_smoothness_long",
+		.data		= &sched_burst_smoothness_long,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "sched_burst_smoothness_short",
+		.data		= &sched_burst_smoothness_short,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "sched_burst_fork_atavistic",
+		.data		= &sched_burst_fork_atavistic,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_THREE,
+	},
+	{
+		.procname	= "sched_burst_penalty_offset",
+		.data		= &sched_burst_penalty_offset,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &sixty_four,
+	},
+	{
+		.procname	= "sched_burst_penalty_scale",
+		.data		= &sched_burst_penalty_scale,
+		.maxlen		= sizeof(uint),
+		.mode		= 0644,
+		.proc_handler = proc_douintvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &maxval_12_bits,
+	},
+	{
+		.procname	= "sched_burst_cache_lifetime",
+		.data		= &sched_burst_cache_lifetime,
+		.maxlen		= sizeof(uint),
+		.mode		= 0644,
+		.proc_handler = proc_douintvec,
+	},
+#endif // CONFIG_SCHED_BORE
 #ifdef CONFIG_CFS_BANDWIDTH
 	{
 		.procname       = "sched_cfs_bandwidth_slice_us",
@@ -195,6 +366,13 @@ static inline void update_load_set(struct load_weight *lw, unsigned long w)
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
+#ifdef CONFIG_SCHED_BORE
+static void update_sysctl(void) {
+	sysctl_sched_base_slice =
+		max(sysctl_sched_min_base_slice, configured_sched_base_slice);
+}
+void sched_update_min_base_slice(void) { update_sysctl(); }
+#else // !CONFIG_SCHED_BORE
 static unsigned int get_update_sysctl_factor(void)
 {
 	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
@@ -225,6 +403,7 @@ static void update_sysctl(void)
 	SET_SYSCTL(sched_base_slice);
 #undef SET_SYSCTL
 }
+#endif // CONFIG_SCHED_BORE
 
 void __init sched_init_granularity(void)
 {
@@ -702,6 +881,9 @@ static s64 entity_lag(u64 avruntime, struct sched_entity *se)
 
 	vlag = avruntime - se->vruntime;
 	limit = calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se);
+#ifdef CONFIG_SCHED_BORE
+	limit >>= 1;
+#endif // CONFIG_SCHED_BORE
 
 	return clamp(vlag, -limit, limit);
 }
@@ -862,6 +1044,39 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 	return __node_2_se(left);
 }
 
+static inline bool pick_curr(struct cfs_rq *cfs_rq,
+			     struct sched_entity *curr, struct sched_entity *wakee)
+{
+	/*
+	 * Nothing to preserve...
+	 */
+	if (!curr || !sched_feat(RESPECT_SLICE))
+		return false;
+
+	/*
+	 * Allow preemption at the 0-lag point -- even if not all of the slice
+	 * is consumed. Note: placement of positive lag can push V left and render
+	 * @curr instantly ineligible irrespective the time on-cpu.
+	 */
+	if (sched_feat(RUN_TO_PARITY) && !entity_eligible(cfs_rq, curr))
+		return false;
+
+	/*
+	 * Don't preserve @curr when the @wakee has a shorter slice and earlier
+	 * deadline. IOW, explicitly allow preemption.
+	 */
+	if (sched_feat(PREEMPT_SHORT) && wakee &&
+	    wakee->slice < curr->slice &&
+	    (s64)(wakee->deadline - curr->deadline) < 0)
+		return false;
+
+	/*
+	 * Preserve @curr to allow it to finish its first slice.
+	 * See the HACK in set_next_entity().
+	 */
+	return curr->vlag == curr->deadline;
+}
+
 /*
  * Earliest Eligible Virtual Deadline First
  *
@@ -881,28 +1096,27 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
  *
  * Which allows tree pruning through eligibility.
  */
-static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
+static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *wakee)
 {
 	struct rb_node *node = cfs_rq->tasks_timeline.rb_root.rb_node;
 	struct sched_entity *se = __pick_first_entity(cfs_rq);
 	struct sched_entity *curr = cfs_rq->curr;
 	struct sched_entity *best = NULL;
 
+	if (curr && !curr->on_rq)
+		curr = NULL;
+
 	/*
 	 * We can safely skip eligibility check if there is only one entity
 	 * in this cfs_rq, saving some cycles.
 	 */
 	if (cfs_rq->nr_running == 1)
-		return curr && curr->on_rq ? curr : se;
-
-	if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr)))
-		curr = NULL;
+		return curr ?: se;
 
 	/*
-	 * Once selected, run a task until it either becomes non-eligible or
-	 * until it gets a new slice. See the HACK in set_next_entity().
+	 * Preserve @curr to let it finish its slice.
 	 */
-	if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline)
+	if (pick_curr(cfs_rq, curr, wakee))
 		return curr;
 
 	/* Pick the leftmost entity if it's eligible */
@@ -961,6 +1175,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
  * Scheduling class statistics methods:
  */
 #ifdef CONFIG_SMP
+#if !defined(CONFIG_SCHED_BORE)
 int sched_update_scaling(void)
 {
 	unsigned int factor = get_update_sysctl_factor();
@@ -972,6 +1187,7 @@ int sched_update_scaling(void)
 
 	return 0;
 }
+#endif // CONFIG_SCHED_BORE
 #endif
 #endif
 
@@ -1171,7 +1387,13 @@ static void update_curr(struct cfs_rq *cfs_rq)
 	if (unlikely(delta_exec <= 0))
 		return;
 
+#ifdef CONFIG_SCHED_BORE
+	curr->burst_time += delta_exec;
+	update_burst_penalty(curr);
+	curr->vruntime += max(1ULL, calc_delta_fair(delta_exec, curr));
+#else // !CONFIG_SCHED_BORE
 	curr->vruntime += calc_delta_fair(delta_exec, curr);
+#endif // CONFIG_SCHED_BORE
 	update_deadline(cfs_rq, curr);
 	update_min_vruntime(cfs_rq);
 
@@ -5183,6 +5405,9 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	 *
 	 * EEVDF: placement strategy #1 / #2
 	 */
+#ifdef CONFIG_SCHED_BORE
+	if (se->vlag)
+#endif // CONFIG_SCHED_BORE
 	if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
 		struct sched_entity *curr = cfs_rq->curr;
 		unsigned long load;
@@ -5472,7 +5697,7 @@ pick_next_entity(struct cfs_rq *cfs_rq)
 	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
 		return cfs_rq->next;
 
-	return pick_eevdf(cfs_rq);
+	return pick_eevdf(cfs_rq, NULL);
 }
 
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
@@ -6835,6 +7060,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	bool was_sched_idle = sched_idle_rq(rq);
 
 	util_est_dequeue(&rq->cfs, p);
+#ifdef CONFIG_SCHED_BORE
+	if (task_sleep) {
+		cfs_rq = cfs_rq_of(se);
+		if (cfs_rq->curr == se)
+			update_curr(cfs_rq);
+		restart_burst(se);
+	}
+#endif // CONFIG_SCHED_BORE
 
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
@@ -8369,10 +8602,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	cfs_rq = cfs_rq_of(se);
 	update_curr(cfs_rq);
 
-	/*
-	 * XXX pick_eevdf(cfs_rq) != se ?
-	 */
-	if (pick_eevdf(cfs_rq) == pse)
+	if (pick_eevdf(cfs_rq, pse) == pse)
 		goto preempt;
 
 	return;
@@ -8590,16 +8820,25 @@ static void yield_task_fair(struct rq *rq)
 	/*
 	 * Are we the only task in the tree?
 	 */
+#if !defined(CONFIG_SCHED_BORE)
 	if (unlikely(rq->nr_running == 1))
 		return;
 
 	clear_buddies(cfs_rq, se);
+#endif // CONFIG_SCHED_BORE
 
 	update_rq_clock(rq);
 	/*
 	 * Update run-time statistics of the 'current'.
 	 */
 	update_curr(cfs_rq);
+#ifdef CONFIG_SCHED_BORE
+	restart_burst_rescale_deadline(se);
+	if (unlikely(rq->nr_running == 1))
+		return;
+
+	clear_buddies(cfs_rq, se);
+#endif // CONFIG_SCHED_BORE
 	/*
 	 * Tell update_rq_clock() that we've just updated,
 	 * so we don't do microscopic update in schedule()
@@ -12660,6 +12899,9 @@ static void task_fork_fair(struct task_struct *p)
 	curr = cfs_rq->curr;
 	if (curr)
 		update_curr(cfs_rq);
+#ifdef CONFIG_SCHED_BORE
+	update_burst_score(se);
+#endif // CONFIG_SCHED_BORE
 	place_entity(cfs_rq, se, ENQUEUE_INITIAL);
 	rq_unlock(rq, &rf);
 }
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 143f55df890b1..bfeb9f65383d9 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -5,8 +5,26 @@
  * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled.
  */
 SCHED_FEAT(PLACE_LAG, true)
+/*
+ * Give new tasks half a slice to ease into the competition.
+ */
 SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
-SCHED_FEAT(RUN_TO_PARITY, true)
+/*
+ * Inhibit (wakeup) preemption until the current task has exhausted its slice.
+ */
+#ifdef CONFIG_SCHED_BORE
+SCHED_FEAT(RESPECT_SLICE, false)
+#else // !CONFIG_SCHED_BORE
+SCHED_FEAT(RESPECT_SLICE, true)
+#endif // CONFIG_SCHED_BORE
+/*
+ * Relax RESPECT_SLICE to allow preemption once current has reached 0-lag.
+ */
+SCHED_FEAT(RUN_TO_PARITY, false)
+/*
+ * Allow tasks with a shorter slice to disregard RESPECT_SLICE
+ */
+SCHED_FEAT(PREEMPT_SHORT, true)
 
 /*
  * Prefer to schedule the task we woke last (assuming it failed
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ae50f212775e5..8c976d27f6e9c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1967,7 +1967,11 @@ static inline void dirty_sched_domain_sysctl(int cpu)
 }
 #endif
 
+#ifdef CONFIG_SCHED_BORE
+extern void sched_update_min_base_slice(void);
+#else // !CONFIG_SCHED_BORE
 extern int sched_update_scaling(void);
+#endif // CONFIG_SCHED_BORE
 
 static inline const struct cpumask *task_user_cpus(struct task_struct *p)
 {
@@ -2554,6 +2558,9 @@ extern const_debug unsigned int sysctl_sched_nr_migrate;
 extern const_debug unsigned int sysctl_sched_migration_cost;
 
 extern unsigned int sysctl_sched_base_slice;
+#ifdef CONFIG_SCHED_BORE
+extern unsigned int sysctl_sched_min_base_slice;
+#endif // CONFIG_SCHED_BORE
 
 #ifdef CONFIG_SCHED_DEBUG
 extern int sysctl_resched_latency_warn_ms;
-- 
2.45.1