On Mon, 3 Feb 2025 09:34:29 +0100
Vlastimil Babka [off-list ref] wrote:

On 1/30/25 19:16, Wander Lairson Costa wrote:

quoted

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.

quoted

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 <redacted>  

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

No objections but...

Thanks,
Vlastimil

quoted

---
 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

quoted

 		__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),