sched_ext: Take out ->priq and ->flags from scx_dsq_node

struct scx_dsq_node contains two data structure nodes to link the containing
task to a DSQ and a flags field that is protected by the lock of the
associated DSQ. One reason why they are grouped into a struct is to use the
type independently as a cursor node when iterating tasks on a DSQ. However,
when iterating, the cursor only needs to be linked on the FIFO list and the
rb_node part ends up inflating the size of the iterator data structure
unnecessarily making it potentially too expensive to place it on stack.

Take ->priq and ->flags out of scx_dsq_node and put them in sched_ext_entity
as ->dsq_priq and ->dsq_flags, respectively. scx_dsq_node is renamed to
scx_dsq_list_node and the field names are renamed accordingly. This will
help implementing DSQ task iterator that can be allocated on stack.

No functional change intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: David Vernet <void@manifault.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
index fe9a67ffe6b1..eb9cfd18a923 100644
--- a/include/linux/sched/ext.h
+++ b/include/linux/sched/ext.h
@@ -121,10 +121,8 @@ enum scx_kf_mask {
 	__SCX_KF_TERMINAL	= SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU | SCX_KF_REST,
 };
 
-struct scx_dsq_node {
-	struct list_head	list;		/* dispatch order */
-	struct rb_node		priq;		/* p->scx.dsq_vtime order */
-	u32			flags;		/* SCX_TASK_DSQ_* flags */
+struct scx_dsq_list_node {
+	struct list_head	node;
 };
 
 /*
@@ -133,7 +131,9 @@ struct scx_dsq_node {
  */
 struct sched_ext_entity {
 	struct scx_dispatch_q	*dsq;
-	struct scx_dsq_node	dsq_node;	/* protected by dsq lock */
+	struct scx_dsq_list_node dsq_list;	/* dispatch order */
+	struct rb_node		dsq_priq;	/* p->scx.dsq_vtime order */
+	u32			dsq_flags;	/* protected by DSQ lock */
 	u32			flags;		/* protected by rq lock */
 	u32			weight;
 	s32			sticky_cpu;