linux-kernel - Re: [PATCH v5 6/6] sched_ext: Use time helpers in BPF schedulers

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Message-ID: <Z1_Y7WdR5ete7W-D@gpd3>
Date: Mon, 16 Dec 2024 08:38:21 +0100
From: Andrea Righi <arighi@...dia.com>
To: Changwoo Min <multics69@...il.com>
Cc: tj@...nel.org, void@...ifault.com, mingo@...hat.com,
	peterz@...radead.org, kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org, Changwoo Min <changwoo@...lia.com>
Subject: Re: [PATCH v5 6/6] sched_ext: Use time helpers in BPF schedulers

On Mon, Dec 16, 2024 at 12:11:44PM +0900, Changwoo Min wrote:
> Modify the BPF schedulers to use time helpers defined in common.bpf.h
> 
> Signed-off-by: Changwoo Min <changwoo@...lia.com>

Ditto (about having the same change in the scx repo), as mentioned in
PATCH 4/6.

-Andrea

> ---
>  tools/sched_ext/scx_central.bpf.c |  5 -----
>  tools/sched_ext/scx_flatcg.bpf.c  | 11 +++--------
>  tools/sched_ext/scx_simple.bpf.c  |  5 -----
>  3 files changed, 3 insertions(+), 18 deletions(-)
> 
> diff --git a/tools/sched_ext/scx_central.bpf.c b/tools/sched_ext/scx_central.bpf.c
> index ea1d853b9dd4..c3b6998ea83e 100644
> --- a/tools/sched_ext/scx_central.bpf.c
> +++ b/tools/sched_ext/scx_central.bpf.c
> @@ -87,11 +87,6 @@ struct {
>  	__type(value, struct central_timer);
>  } central_timer SEC(".maps");
>  
> -static bool vtime_before(u64 a, u64 b)
> -{
> -	return (s64)(a - b) < 0;
> -}
> -
>  s32 BPF_STRUCT_OPS(central_select_cpu, struct task_struct *p,
>  		   s32 prev_cpu, u64 wake_flags)
>  {
> diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
> index 85e33e45f818..2735ec25e511 100644
> --- a/tools/sched_ext/scx_flatcg.bpf.c
> +++ b/tools/sched_ext/scx_flatcg.bpf.c
> @@ -137,11 +137,6 @@ static u64 div_round_up(u64 dividend, u64 divisor)
>  	return (dividend + divisor - 1) / divisor;
>  }
>  
> -static bool vtime_before(u64 a, u64 b)
> -{
> -	return (s64)(a - b) < 0;
> -}
> -
>  static bool cgv_node_less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
>  {
>  	struct cgv_node *cgc_a, *cgc_b;
> @@ -920,14 +915,14 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p,
>  		    struct cgroup *from, struct cgroup *to)
>  {
>  	struct fcg_cgrp_ctx *from_cgc, *to_cgc;
> -	s64 vtime_delta;
> +	s64 delta;
>  
>  	/* find_cgrp_ctx() triggers scx_ops_error() on lookup failures */
>  	if (!(from_cgc = find_cgrp_ctx(from)) || !(to_cgc = find_cgrp_ctx(to)))
>  		return;
>  
> -	vtime_delta = p->scx.dsq_vtime - from_cgc->tvtime_now;
> -	p->scx.dsq_vtime = to_cgc->tvtime_now + vtime_delta;
> +	delta = vtime_delta(p->scx.dsq_vtime, from_cgc->tvtime_now);
> +	p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
>  }
>  
>  s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)
> diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
> index 31f915b286c6..6561d400ae6d 100644
> --- a/tools/sched_ext/scx_simple.bpf.c
> +++ b/tools/sched_ext/scx_simple.bpf.c
> @@ -52,11 +52,6 @@ static void stat_inc(u32 idx)
>  		(*cnt_p)++;
>  }
>  
> -static inline bool vtime_before(u64 a, u64 b)
> -{
> -	return (s64)(a - b) < 0;
> -}
> -
>  s32 BPF_STRUCT_OPS(simple_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)
>  {
>  	bool is_idle = false;
> -- 
> 2.47.1
>