Commit c9c809f4 authored by Tejun Heo's avatar Tejun Heo
Browse files

scx_flatcg: Use a user DSQ for fallback instead of SCX_DSQ_GLOBAL 



scx_flatcg was using SCX_DSQ_GLOBAL for fallback handling. However, it is
assuming that SCX_DSQ_GLOBAL isn't automatically consumed, which was true a
while ago but is no longer the case. Also, there are further changes planned
for SCX_DSQ_GLOBAL which will disallow explicit consumption from it. Switch
to a user DSQ for fallback.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Vernet <void@manifault.com>
parent a748db0c

tools/sched_ext/scx_flatcg.bpf.c

+13 −4
Original line number Diff line number Diff line
@@ -49,7 +49,10 @@ 
/*

 * Maximum amount of retries to find a valid cgroup.

 */

#define CGROUP_MAX_RETRIES 1024

enum {

	FALLBACK_DSQ		= 0,

	CGROUP_MAX_RETRIES	= 1024,

};



char _license[] SEC("license") = "GPL";
@@ -377,7 +380,7 @@ void BPF_STRUCT_OPS(fcg_enqueue, struct task_struct *p, u64 enq_flags) 
			scx_bpf_dispatch(p, SCX_DSQ_LOCAL, SCX_SLICE_DFL, enq_flags);

		} else {

			stat_inc(FCG_STAT_GLOBAL);

			scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags);

			scx_bpf_dispatch(p, FALLBACK_DSQ, SCX_SLICE_DFL, enq_flags);

		}

		return;

	}
@@ -780,7 +783,7 @@ void BPF_STRUCT_OPS(fcg_dispatch, s32 cpu, struct task_struct *prev) 
pick_next_cgroup:

	cpuc->cur_at = now;



	if (scx_bpf_consume(SCX_DSQ_GLOBAL)) {

	if (scx_bpf_consume(FALLBACK_DSQ)) {

		cpuc->cur_cgid = 0;

		return;

	}
@@ -837,7 +840,7 @@ int BPF_STRUCT_OPS_SLEEPABLE(fcg_cgroup_init, struct cgroup *cgrp, 
	int ret;



	/*

	 * Technically incorrect as cgroup ID is full 64bit while dq ID is

	 * Technically incorrect as cgroup ID is full 64bit while dsq ID is

	 * 63bit. Should not be a problem in practice and easy to spot in the

	 * unlikely case that it breaks.

	 */
@@ -925,6 +928,11 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p, 
	p->scx.dsq_vtime = to_cgc->tvtime_now + vtime_delta;

}



s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)

{

	return scx_bpf_create_dsq(FALLBACK_DSQ, -1);

}



void BPF_STRUCT_OPS(fcg_exit, struct scx_exit_info *ei)

{

	UEI_RECORD(uei, ei);
@@ -943,6 +951,7 @@ SCX_OPS_DEFINE(flatcg_ops, 
	       .cgroup_init		= (void *)fcg_cgroup_init,

	       .cgroup_exit		= (void *)fcg_cgroup_exit,

	       .cgroup_move		= (void *)fcg_cgroup_move,

	       .init			= (void *)fcg_init,

	       .exit			= (void *)fcg_exit,

	       .flags			= SCX_OPS_HAS_CGROUP_WEIGHT | SCX_OPS_ENQ_EXITING,

	       .name			= "flatcg");