linuxmsm/laptops-kernel
0
0
Fork 0
mirror of https://github.com/linux-msm/laptops-kernel.git synced 2026-08-13 14:19:53 -07:00
Code Issues Packages Projects Releases Wiki Activity

sched_ext: Add SCX_OPS_ALWAYS_ENQ_IMMED ops flag

Browse Source 
SCX_ENQ_IMMED makes enqueue to local DSQs succeed only if the task can start
running immediately. Otherwise, the task is re-enqueued through ops.enqueue().
This provides tighter control but requires specifying the flag on every
insertion.

Add SCX_OPS_ALWAYS_ENQ_IMMED ops flag. When set, SCX_ENQ_IMMED is
automatically applied to all local DSQ enqueues including through
scx_bpf_dsq_move_to_local().

scx_qmap is updated with -I option to test the feature and -F option for
IMMED stress testing which forces every Nth enqueue to a busy local DSQ.

v2: - Cover scx_bpf_dsq_move_to_local() path (now has enq_flags via ___v2).
    - scx_qmap: Remove sched_switch and cpu_release handlers (superseded by
      kernel-side wakeup_preempt_scx()). Add -F for IMMED stress testing.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo
2026-03-13 09:43:23 -10:00
parent 860683763e
commit 3229ac4a5e
5 changed files with 65 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/sched/ext.c
+18 -13
View File
@@ -7755,20 +7755,25 @@ void __init init_sched_ext_class(void)
/********************************************************************************
* Helpers that can be called from the BPF scheduler.
*/
static bool scx_vet_enq_flags(struct scx_sched *sch, u64 dsq_id, u64 enq_flags)
static bool scx_vet_enq_flags(struct scx_sched *sch, u64 dsq_id, u64 *enq_flags)
{
if ((enq_flags & SCX_ENQ_IMMED) &&
unlikely(dsq_id != SCX_DSQ_LOCAL &&
(dsq_id & SCX_DSQ_LOCAL_ON) != SCX_DSQ_LOCAL_ON)) {
scx_error(sch, "SCX_ENQ_IMMED on a non-local DSQ 0x%llx", dsq_id);
return false;
bool is_local = dsq_id == SCX_DSQ_LOCAL ||
(dsq_id & SCX_DSQ_LOCAL_ON) == SCX_DSQ_LOCAL_ON;
if (*enq_flags & SCX_ENQ_IMMED) {
if (unlikely(!is_local)) {
scx_error(sch, "SCX_ENQ_IMMED on a non-local DSQ 0x%llx", dsq_id);
return false;
}
} else if ((sch->ops.flags & SCX_OPS_ALWAYS_ENQ_IMMED) && is_local) {
*enq_flags |= SCX_ENQ_IMMED;
}
return true;
}
static bool scx_dsq_insert_preamble(struct scx_sched *sch, struct task_struct *p,
u64 dsq_id, u64 enq_flags)
u64 dsq_id, u64 *enq_flags)
{
if (!scx_kf_allowed(sch, SCX_KF_ENQUEUE | SCX_KF_DISPATCH))
return false;
@@ -7780,8 +7785,8 @@ static bool scx_dsq_insert_preamble(struct scx_sched *sch, struct task_struct *p
return false;
}
if (unlikely(enq_flags & __SCX_ENQ_INTERNAL_MASK)) {
scx_error(sch, "invalid enq_flags 0x%llx", enq_flags);
if (unlikely(*enq_flags & __SCX_ENQ_INTERNAL_MASK)) {
scx_error(sch, "invalid enq_flags 0x%llx", *enq_flags);
return false;
}
@@ -7875,7 +7880,7 @@ __bpf_kfunc bool scx_bpf_dsq_insert___v2(struct task_struct *p, u64 dsq_id,
if (unlikely(!sch))
return false;
if (!scx_dsq_insert_preamble(sch, p, dsq_id, enq_flags))
if (!scx_dsq_insert_preamble(sch, p, dsq_id, &enq_flags))
return false;
if (slice)
@@ -7901,7 +7906,7 @@ __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id,
static bool scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p,
u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags)
{
if (!scx_dsq_insert_preamble(sch, p, dsq_id, enq_flags))
if (!scx_dsq_insert_preamble(sch, p, dsq_id, &enq_flags))
return false;
if (slice)
@@ -8028,7 +8033,7 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit,
!scx_kf_allowed(sch, SCX_KF_DISPATCH))
return false;
if (!scx_vet_enq_flags(sch, dsq_id, enq_flags))
if (!scx_vet_enq_flags(sch, dsq_id, &enq_flags))
return false;
/*
@@ -8189,7 +8194,7 @@ __bpf_kfunc bool scx_bpf_dsq_move_to_local___v2(u64 dsq_id, u64 enq_flags,
if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
return false;
if (!scx_vet_enq_flags(sch, SCX_DSQ_LOCAL, enq_flags))
if (!scx_vet_enq_flags(sch, SCX_DSQ_LOCAL, &enq_flags))
return false;
dspc = &this_cpu_ptr(sch->pcpu)->dsp_ctx;
kernel/sched/ext_internal.h
+8 -1
View File
@@ -182,13 +182,20 @@ enum scx_ops_flags {
*/
SCX_OPS_BUILTIN_IDLE_PER_NODE = 1LLU << 6,
/*
* If set, %SCX_ENQ_IMMED is assumed to be set on all local DSQ
* enqueues.
*/
SCX_OPS_ALWAYS_ENQ_IMMED = 1LLU << 7,
SCX_OPS_ALL_FLAGS = SCX_OPS_KEEP_BUILTIN_IDLE |
SCX_OPS_ENQ_LAST |
SCX_OPS_ENQ_EXITING |
SCX_OPS_ENQ_MIGRATION_DISABLED |
SCX_OPS_ALLOW_QUEUED_WAKEUP |
SCX_OPS_SWITCH_PARTIAL |
SCX_OPS_BUILTIN_IDLE_PER_NODE,
SCX_OPS_BUILTIN_IDLE_PER_NODE |
SCX_OPS_ALWAYS_ENQ_IMMED,
/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
__SCX_OPS_INTERNAL_MASK = 0xffLLU << 56,
tools/sched_ext/include/scx/compat.h
+1
View File
@@ -116,6 +116,7 @@ static inline bool __COMPAT_struct_has_field(const char *type, const char *field
#define SCX_OPS_ENQ_MIGRATION_DISABLED SCX_OPS_FLAG(SCX_OPS_ENQ_MIGRATION_DISABLED)
#define SCX_OPS_ALLOW_QUEUED_WAKEUP SCX_OPS_FLAG(SCX_OPS_ALLOW_QUEUED_WAKEUP)
#define SCX_OPS_BUILTIN_IDLE_PER_NODE SCX_OPS_FLAG(SCX_OPS_BUILTIN_IDLE_PER_NODE)
#define SCX_OPS_ALWAYS_ENQ_IMMED SCX_OPS_FLAG(SCX_OPS_ALWAYS_ENQ_IMMED)
#define SCX_PICK_IDLE_FLAG(name) __COMPAT_ENUM_OR_ZERO("scx_pick_idle_cpu_flags", #name)
tools/sched_ext/scx_qmap.bpf.c
+27 -39
View File
@@ -11,8 +11,6 @@
*
* - BPF-side queueing using PIDs.
* - Sleepable per-task storage allocation using ops.prep_enable().
* - Using ops.cpu_release() to handle a higher priority scheduling class taking
* the CPU away.
* - Core-sched support.
*
* This scheduler is primarily for demonstration and testing of sched_ext
@@ -47,6 +45,8 @@ const volatile bool print_msgs;
const volatile u64 sub_cgroup_id;
const volatile s32 disallow_tgid;
const volatile bool suppress_dump;
const volatile bool always_enq_immed;
const volatile u32 immed_stress_nth;
u64 nr_highpri_queued;
u32 test_error_cnt;
@@ -144,8 +144,10 @@ static s32 pick_direct_dispatch_cpu(struct task_struct *p, s32 prev_cpu)
{
s32 cpu;
if (p->nr_cpus_allowed == 1 ||
scx_bpf_test_and_clear_cpu_idle(prev_cpu))
if (!always_enq_immed && p->nr_cpus_allowed == 1)
return prev_cpu;
if (scx_bpf_test_and_clear_cpu_idle(prev_cpu))
return prev_cpu;
cpu = scx_bpf_pick_idle_cpu(p->cpus_ptr, 0);
@@ -238,6 +240,22 @@ void BPF_STRUCT_OPS(qmap_enqueue, struct task_struct *p, u64 enq_flags)
*/
tctx->core_sched_seq = core_sched_tail_seqs[idx]++;
/*
* IMMED stress testing: Every immed_stress_nth'th enqueue, dispatch
* directly to prev_cpu's local DSQ even when busy to force dsq->nr > 1
* and exercise the kernel IMMED reenqueue trigger paths.
*/
if (immed_stress_nth && !(enq_flags & SCX_ENQ_REENQ)) {
static u32 immed_stress_cnt;
if (!(++immed_stress_cnt % immed_stress_nth)) {
tctx->force_local = false;
scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL_ON | scx_bpf_task_cpu(p),
slice_ns, enq_flags);
return;
}
}
/*
* If qmap_select_cpu() is telling us to or this is the last runnable
* task on the CPU, enqueue locally.
@@ -558,40 +576,11 @@ bool BPF_STRUCT_OPS(qmap_core_sched_before,
return task_qdist(a) > task_qdist(b);
}
SEC("tp_btf/sched_switch")
int BPF_PROG(qmap_sched_switch, bool preempt, struct task_struct *prev,
struct task_struct *next, unsigned long prev_state)
{
if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
return 0;
/*
* If @cpu is taken by a higher priority scheduling class, it is no
* longer available for executing sched_ext tasks. As we don't want the
* tasks in @cpu's local dsq to sit there until @cpu becomes available
* again, re-enqueue them into the global dsq. See %SCX_ENQ_REENQ
* handling in qmap_enqueue().
*/
switch (next->policy) {
case 1: /* SCHED_FIFO */
case 2: /* SCHED_RR */
case 6: /* SCHED_DEADLINE */
scx_bpf_reenqueue_local();
/* trigger re-enqueue on CPU0 just to exercise LOCAL_ON */
if (__COMPAT_has_generic_reenq())
scx_bpf_dsq_reenq(SCX_DSQ_LOCAL_ON | 0, 0);
}
return 0;
}
void BPF_STRUCT_OPS(qmap_cpu_release, s32 cpu, struct scx_cpu_release_args *args)
{
/* see qmap_sched_switch() to learn how to do this on newer kernels */
if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
scx_bpf_reenqueue_local();
}
/*
* sched_switch tracepoint and cpu_release handlers are no longer needed.
* With SCX_OPS_ALWAYS_ENQ_IMMED, wakeup_preempt_scx() reenqueues IMMED
* tasks when a higher-priority scheduling class takes the CPU.
*/
s32 BPF_STRUCT_OPS(qmap_init_task, struct task_struct *p,
struct scx_init_task_args *args)
@@ -999,7 +988,6 @@ SCX_OPS_DEFINE(qmap_ops,
.dispatch = (void *)qmap_dispatch,
.tick = (void *)qmap_tick,
.core_sched_before = (void *)qmap_core_sched_before,
.cpu_release = (void *)qmap_cpu_release,
.init_task = (void *)qmap_init_task,
.dump = (void *)qmap_dump,
.dump_cpu = (void *)qmap_dump_cpu,
tools/sched_ext/scx_qmap.c
+11 -2
View File
@@ -21,7 +21,7 @@ const char help_fmt[] =
"See the top-level comment in .bpf.c for more details.\n"
"\n"
"Usage: %s [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-l COUNT] [-b COUNT]\n"
" [-P] [-M] [-H] [-d PID] [-D LEN] [-S] [-p] [-v]\n"
" [-P] [-M] [-H] [-d PID] [-D LEN] [-S] [-p] [-I] [-F COUNT] [-v]\n"
"\n"
" -s SLICE_US Override slice duration\n"
" -e COUNT Trigger scx_bpf_error() after COUNT enqueues\n"
@@ -36,6 +36,8 @@ const char help_fmt[] =
" -D LEN Set scx_exit_info.dump buffer length\n"
" -S Suppress qmap-specific debug dump\n"
" -p Switch only tasks on SCHED_EXT policy instead of all\n"
" -I Turn on SCX_OPS_ALWAYS_ENQ_IMMED\n"
" -F COUNT IMMED stress: force every COUNT'th enqueue to a busy local DSQ (use with -I)\n"
" -v Print libbpf debug messages\n"
" -h Display this help and exit\n";
@@ -68,7 +70,7 @@ int main(int argc, char **argv)
skel->rodata->slice_ns = __COMPAT_ENUM_OR_ZERO("scx_public_consts", "SCX_SLICE_DFL");
while ((opt = getopt(argc, argv, "s:e:t:T:l:b:PMHc:d:D:Spvh")) != -1) {
while ((opt = getopt(argc, argv, "s:e:t:T:l:b:PMHc:d:D:SpIF:vh")) != -1) {
switch (opt) {
case 's':
skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000;
@@ -121,6 +123,13 @@ int main(int argc, char **argv)
case 'p':
skel->struct_ops.qmap_ops->flags |= SCX_OPS_SWITCH_PARTIAL;
break;
case 'I':
skel->rodata->always_enq_immed = true;
skel->struct_ops.qmap_ops->flags |= SCX_OPS_ALWAYS_ENQ_IMMED;
break;
case 'F':
skel->rodata->immed_stress_nth = strtoul(optarg, NULL, 0);
break;
case 'v':
verbose = true;
break;