linux-kernel - Re: [PATCH v2 1/2] mm: memcg: print out cgroup name in the memcg tracepoints

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Message-ID: <20231123072126.jpukmc6rqmzckdw2@google.com>
Date:   Thu, 23 Nov 2023 07:21:26 +0000
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Dmitry Rokosov <ddrokosov@...utedevices.com>
Cc:     rostedt@...dmis.org, mhiramat@...nel.org, hannes@...xchg.org,
        mhocko@...nel.org, roman.gushchin@...ux.dev, muchun.song@...ux.dev,
        akpm@...ux-foundation.org, kernel@...rdevices.ru,
        rockosov@...il.com, cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: memcg: print out cgroup name in the memcg tracepoints

On Wed, Nov 22, 2023 at 01:01:55PM +0300, Dmitry Rokosov wrote:
> Sometimes it is necessary to understand in which memcg tracepoint event
> occurred. The function cgroup_name() is a useful tool for this purpose.
> To integrate cgroup_name() into the existing memcg tracepoints, this
> patch introduces a new tracepoint template for the begin() and end()
> events, utilizing static __array() to store the cgroup name.
> 
> Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> ---
>  include/trace/events/vmscan.h | 77 +++++++++++++++++++++++++++++------
>  mm/vmscan.c                   | 10 ++---
>  2 files changed, 70 insertions(+), 17 deletions(-)
> 
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index d2123dd960d5..9b49cd120ae9 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -141,19 +141,47 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_direct_reclaim_b
>  );
>  
>  #ifdef CONFIG_MEMCG
> -DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_memcg_reclaim_begin,
>  
> -	TP_PROTO(int order, gfp_t gfp_flags),
> +DECLARE_EVENT_CLASS(mm_vmscan_memcg_reclaim_begin_template,
>  
> -	TP_ARGS(order, gfp_flags)
> +	TP_PROTO(int order, gfp_t gfp_flags, const struct mem_cgroup *memcg),
> +
> +	TP_ARGS(order, gfp_flags, memcg),
> +
> +	TP_STRUCT__entry(
> +		__field(int, order)
> +		__field(unsigned long, gfp_flags)
> +		__array(char, name, NAME_MAX + 1)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->order = order;
> +		__entry->gfp_flags = (__force unsigned long)gfp_flags;
> +		cgroup_name(memcg->css.cgroup,
> +			__entry->name,
> +			sizeof(__entry->name));

Any reason not to use cgroup_ino? cgroup_name may conflict and be
ambiguous.