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scx_flatcg: Use a user DSQ for fallback instead of SCX_DSQ_GLOBAL

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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: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
This commit is contained in:
Tejun Heo 2024-09-26 12:56:46 -10:00
parent a748db0c8c
commit c9c809f413
1 changed files with 13 additions and 4 deletions
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17
tools/sched_ext/scx_flatcg.bpf.c
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@ -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");