linux-kernel - Re: [PATCH v4 2/2] sched/numa: Add tracepoint that tracks the skipping of numa balancing due to cpuset memory pinning

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Message-ID: <20250423201829.17d4c382@gandalf.local.home>
Date: Wed, 23 Apr 2025 20:18:29 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Libo Chen <libo.chen@...cle.com>
Cc: akpm@...ux-foundation.org, peterz@...radead.org, mgorman@...e.de,
 mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 tj@...nel.org, llong@...hat.com, sraithal@....com, venkat88@...ux.ibm.com,
 kprateek.nayak@....com, raghavendra.kt@....com, yu.c.chen@...el.com,
 tim.c.chen@...el.com, vineethr@...ux.ibm.com, chris.hyser@...cle.com,
 daniel.m.jordan@...cle.com, lorenzo.stoakes@...cle.com, mkoutny@...e.com,
 linux-mm@...ck.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] sched/numa: Add tracepoint that tracks the
 skipping of numa balancing due to cpuset memory pinning

On Wed, 23 Apr 2025 17:01:46 -0700
Libo Chen <libo.chen@...cle.com> wrote:

> +++ b/include/trace/events/sched.h
> @@ -745,6 +745,37 @@ TRACE_EVENT(sched_skip_vma_numa,
>  		  __entry->vm_end,
>  		  __print_symbolic(__entry->reason, NUMAB_SKIP_REASON))
>  );
> +
> +TRACE_EVENT(sched_skip_cpuset_numa,
> +
> +	TP_PROTO(struct task_struct *tsk, nodemask_t *mem_allowed_ptr),
> +
> +	TP_ARGS(tsk, mem_allowed_ptr),
> +
> +	TP_STRUCT__entry(
> +		__array( char,		comm,		TASK_COMM_LEN		)
> +		__field( pid_t,		pid					)
> +		__field( pid_t,		tgid					)
> +		__field( pid_t,		ngid					)
> +		__array( unsigned long, mem_allowed, BITS_TO_LONGS(MAX_NUMNODES))
> +	),
> +
> +	TP_fast_assign(
> +		memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
> +		__entry->pid		 = task_pid_nr(tsk);
> +		__entry->tgid		 = task_tgid_nr(tsk);
> +		__entry->ngid		 = task_numa_group_id(tsk);
> +		memcpy(__entry->mem_allowed, mem_allowed_ptr->bits,
> +		       sizeof(__entry->mem_allowed));

Is mem_allowed->bits guaranteed to be the size of BITS_TO_LONGS(MAX_NUM_NODES)
in size? If not, then memcpy will read beyond that size.

-- Steve


> +	),
> +
> +	TP_printk("comm=%s pid=%d tgid=%d ngid=%d mem_nodes_allowed=%*pbl",
> +		  __entry->comm,
> +		  __entry->pid,
> +		  __entry->tgid,
> +		  __entry->ngid,
> +		  MAX_NUMNODES, __entry->mem_allowed)
> +);