[v1] kmem/tracing: Add kmem name to kmem_cache_alloc tracepoint

[PATCH] kmem/tracing: Add kmem name to kmem_cache_alloc tracepoint

Posted by Wander Lairson Costa 10 months, 3 weeks ago

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.

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@redhat.com>
---
 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),
-- 
2.48.1

Re: [PATCH] kmem/tracing: Add kmem name to kmem_cache_alloc tracepoint

Posted by Vlastimil Babka 10 months, 2 weeks ago

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@redhat.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),

Re: [PATCH] kmem/tracing: Add kmem name to kmem_cache_alloc tracepoint

Posted by Steven Rostedt 10 months, 2 weeks ago

On Mon, 3 Feb 2025 09:34:29 +0100
Vlastimil Babka <vbabka@suse.cz> wrote:

> 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@redhat.com>  
> 
> I will take this in the slab tree, unless Steven objects.

No objections but...

> 
> 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		)

The string place holder in the "struct" is 4 bytes and not a pointer. So I
would place it either at the end or next to another "int" to avoid any
holes caused by it being placed next to a 8 byte field.

-- Steve


> >  		__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),