linux-kernel - Re: [PATCH] kmem/tracing: Add kmem name to kmem_cache

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Message-ID: <46e70b3c-6d96-4507-ba17-a52e8362873d@suse.cz>
Date: Mon, 3 Feb 2025 09:34:29 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Wander Lairson Costa <wander@...hat.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 Christian König <christian.koenig@....com>,
 "Darrick J. Wong" <djwong@...nel.org>, Richard Chang
 <richardycc@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
 "open list:TRACING" <linux-kernel@...r.kernel.org>,
 "open list:TRACING" <linux-trace-kernel@...r.kernel.org>,
 David Rientjes <rientjes@...gle.com>, Christoph Lameter <cl@...two.org>,
 Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: Re: [PATCH] kmem/tracing: Add kmem name to kmem_cache_alloc
 tracepoint

On 1/30/25 19:16, Wander Lairson Costa wrote:
> The kmem_cache_free tracepoint includes a "name" field, which allows
> for easy identification and filtering of specific kmem's. However, the
> kmem_cache_alloc tracepoint lacks this field, making it difficult to
> pair corresponding alloc and free events for analysis.

Hm yeah looks like the free one was added in commit 3544de8ee6e48 and their
use case didn't need alloc too, but it makes sense.

> Add the "name" field to kmem_cache_alloc to enable consistent tracking
> and correlation of kmem alloc and free events.
> 
> Signed-off-by: Wander Lairson Costa <wander@...hat.com>

I will take this in the slab tree, unless Steven objects.

Thanks,
Vlastimil

> ---
>  include/trace/events/kmem.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
> index b37eb0a7060f..8ffb022f024c 100644
> --- a/include/trace/events/kmem.h
> +++ b/include/trace/events/kmem.h
> @@ -22,6 +22,7 @@ TRACE_EVENT(kmem_cache_alloc,
>  	TP_STRUCT__entry(
>  		__field(	unsigned long,	call_site	)
>  		__field(	const void *,	ptr		)
> +		__string(	name,		s->name		)
>  		__field(	size_t,		bytes_req	)
>  		__field(	size_t,		bytes_alloc	)
>  		__field(	unsigned long,	gfp_flags	)
> @@ -32,6 +33,7 @@ TRACE_EVENT(kmem_cache_alloc,
>  	TP_fast_assign(
>  		__entry->call_site	= call_site;
>  		__entry->ptr		= ptr;
> +		__assign_str(name);
>  		__entry->bytes_req	= s->object_size;
>  		__entry->bytes_alloc	= s->size;
>  		__entry->gfp_flags	= (__force unsigned long)gfp_flags;
> @@ -41,9 +43,10 @@ TRACE_EVENT(kmem_cache_alloc,
>  					  (s->flags & SLAB_ACCOUNT)) : false;
>  	),
>  
> -	TP_printk("call_site=%pS ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d accounted=%s",
> +	TP_printk("call_site=%pS ptr=%p name=%s bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d accounted=%s",
>  		(void *)__entry->call_site,
>  		__entry->ptr,
> +		__get_str(name),
>  		__entry->bytes_req,
>  		__entry->bytes_alloc,
>  		show_gfp_flags(__entry->gfp_flags),