From 47068309b5777313b6ac84a77d8d10dc7312260a Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Tue, 8 Apr 2025 09:50:42 -0700 Subject: [PATCH 1/3] sched_ext: Use kvzalloc for large exit_dump allocation Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which can require large contiguous memory depending on the implementation. This change prevents allocation failures by allowing the system to fall back to vmalloc when contiguous memory allocation fails. Since this buffer is only used for debugging purposes, physical memory contiguity is not required, making vmalloc a suitable alternative. Cc: stable@vger.kernel.org Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit") Suggested-by: Rik van Riel Signed-off-by: Breno Leitao Acked-by: Andrea Righi Signed-off-by: Tejun Heo --- kernel/sched/ext.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 66bcd40a28ca..db9af6a3c04f 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4623,7 +4623,7 @@ static void scx_ops_bypass(bool bypass) static void free_exit_info(struct scx_exit_info *ei) { - kfree(ei->dump); + kvfree(ei->dump); kfree(ei->msg); kfree(ei->bt); kfree(ei); @@ -4639,7 +4639,7 @@ static struct scx_exit_info *alloc_exit_info(size_t exit_dump_len) ei->bt = kcalloc(SCX_EXIT_BT_LEN, sizeof(ei->bt[0]), GFP_KERNEL); ei->msg = kzalloc(SCX_EXIT_MSG_LEN, GFP_KERNEL); - ei->dump = kzalloc(exit_dump_len, GFP_KERNEL); + ei->dump = kvzalloc(exit_dump_len, GFP_KERNEL); if (!ei->bt || !ei->msg || !ei->dump) { free_exit_info(ei); From e776b26e3701945e0d20a11dc30ecd4da98e8d67 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 7 Apr 2025 13:20:04 -1000 Subject: [PATCH 2/3] sched_ext: Remove cpu.weight / cpu.idle unimplemented warnings sched_ext generates warnings when cpu.weight / cpu.idle are set to non-default values if the BPF scheduler doesn't implement weight support. These warnings don't provide much value while adding constant annoyance. A BPF scheduler may not implement any particular behavior and there's nothing particularly special about missing cgroup weight support. Drop the warnings. Signed-off-by: Tejun Heo --- kernel/sched/ext.c | 41 +---------------------------------------- 1 file changed, 1 insertion(+), 40 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index db9af6a3c04f..21eaf081d336 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -3899,35 +3899,6 @@ bool scx_can_stop_tick(struct rq *rq) DEFINE_STATIC_PERCPU_RWSEM(scx_cgroup_rwsem); static bool scx_cgroup_enabled; -static bool cgroup_warned_missing_weight; -static bool cgroup_warned_missing_idle; - -static void scx_cgroup_warn_missing_weight(struct task_group *tg) -{ - if (scx_ops_enable_state() == SCX_OPS_DISABLED || - cgroup_warned_missing_weight) - return; - - if ((scx_ops.flags & SCX_OPS_HAS_CGROUP_WEIGHT) || !tg->css.parent) - return; - - pr_warn("sched_ext: \"%s\" does not implement cgroup cpu.weight\n", - scx_ops.name); - cgroup_warned_missing_weight = true; -} - -static void scx_cgroup_warn_missing_idle(struct task_group *tg) -{ - if (!scx_cgroup_enabled || cgroup_warned_missing_idle) - return; - - if (!tg->idle) - return; - - pr_warn("sched_ext: \"%s\" does not implement cgroup cpu.idle\n", - scx_ops.name); - cgroup_warned_missing_idle = true; -} int scx_tg_online(struct task_group *tg) { @@ -3937,8 +3908,6 @@ int scx_tg_online(struct task_group *tg) percpu_down_read(&scx_cgroup_rwsem); - scx_cgroup_warn_missing_weight(tg); - if (scx_cgroup_enabled) { if (SCX_HAS_OP(cgroup_init)) { struct scx_cgroup_init_args args = @@ -4076,9 +4045,7 @@ void scx_group_set_weight(struct task_group *tg, unsigned long weight) void scx_group_set_idle(struct task_group *tg, bool idle) { - percpu_down_read(&scx_cgroup_rwsem); - scx_cgroup_warn_missing_idle(tg); - percpu_up_read(&scx_cgroup_rwsem); + /* TODO: Implement ops->cgroup_set_idle() */ } static void scx_cgroup_lock(void) @@ -4272,9 +4239,6 @@ static int scx_cgroup_init(void) percpu_rwsem_assert_held(&scx_cgroup_rwsem); - cgroup_warned_missing_weight = false; - cgroup_warned_missing_idle = false; - /* * scx_tg_on/offline() are excluded through scx_cgroup_rwsem. If we walk * cgroups and init, all online cgroups are initialized. @@ -4284,9 +4248,6 @@ static int scx_cgroup_init(void) struct task_group *tg = css_tg(css); struct scx_cgroup_init_args args = { .weight = tg->scx_weight }; - scx_cgroup_warn_missing_weight(tg); - scx_cgroup_warn_missing_idle(tg); - if ((tg->scx_flags & (SCX_TG_ONLINE | SCX_TG_INITED)) != SCX_TG_ONLINE) continue; From bc08b15b54b8aadbc8a8f413271c07a3f4bead87 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 8 Apr 2025 08:31:12 -1000 Subject: [PATCH 3/3] sched_ext: Mark SCX_OPS_HAS_CGROUP_WEIGHT for deprecation SCX_OPS_HAS_CGROUP_WEIGHT was only used to suppress the missing cgroup weight support warnings. Now that the warnings are removed, the flag doesn't do anything. Mark it for deprecation and remove its usage from scx_flatcg. v2: Actually include the scx_flatcg update. Signed-off-by: Tejun Heo Suggested-and-reviewed-by: Andrea Righi --- kernel/sched/ext.c | 5 ++++- tools/sched_ext/scx_flatcg.bpf.c | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 21eaf081d336..fdbf249d1c68 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -163,7 +163,7 @@ enum scx_ops_flags { /* * CPU cgroup support flags */ - SCX_OPS_HAS_CGROUP_WEIGHT = 1LLU << 16, /* cpu.weight */ + SCX_OPS_HAS_CGROUP_WEIGHT = 1LLU << 16, /* DEPRECATED, will be removed on 6.18 */ SCX_OPS_ALL_FLAGS = SCX_OPS_KEEP_BUILTIN_IDLE | SCX_OPS_ENQ_LAST | @@ -5213,6 +5213,9 @@ static int validate_ops(const struct sched_ext_ops *ops) return -EINVAL; } + if (ops->flags & SCX_OPS_HAS_CGROUP_WEIGHT) + pr_warn("SCX_OPS_HAS_CGROUP_WEIGHT is deprecated and a noop\n"); + return 0; } diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c index 2c720e3ecad5..fdc7170639e6 100644 --- a/tools/sched_ext/scx_flatcg.bpf.c +++ b/tools/sched_ext/scx_flatcg.bpf.c @@ -950,5 +950,5 @@ SCX_OPS_DEFINE(flatcg_ops, .cgroup_move = (void *)fcg_cgroup_move, .init = (void *)fcg_init, .exit = (void *)fcg_exit, - .flags = SCX_OPS_HAS_CGROUP_WEIGHT | SCX_OPS_ENQ_EXITING, + .flags = SCX_OPS_ENQ_EXITING, .name = "flatcg");