fix: mm, tracing: record slab name for kmem_cache_free() (v5.12)

See upstream commit:

  commit 3544de8ee6e4817278b15fe08658de49abf58954
  Author: Jacob Wen <jian.w.wen@oracle.com>
  Date:   Wed Feb 24 12:00:55 2021 -0800

    mm, tracing: record slab name for kmem_cache_free()

    Currently, a trace record generated by the RCU core is as below.

    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=00000000f3b49a66

    It doesn't tell us what the RCU core has freed.

    This patch adds the slab name to trace_kmem_cache_free().
    The new format is as follows.

    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=0000000037f79c8d name=dentry
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=00000000f78cb7b5 name=sock_inode_cache
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=0000000018768985 name=pool_workqueue
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=000000006a6cb484 name=radix_tree_node

    We can use it to understand what the RCU core is going to free. For
    example, some users maybe interested in when the RCU core starts
    freeing reclaimable slabs like dentry to reduce memory pressure.

Link: https://lkml.kernel.org/r/20201216072804.8838-1-jian.w.wen@oracle.com
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1ee2fc476614cadcc8d3ac5d8feddc7910e1aa3a

diff --git a/instrumentation/events/lttng-module/kmem.h b/instrumentation/events/lttng-module/kmem.h
index b134620a92ed13a3e98bb5f66333ef8a155ee77c..d787ea5463e9d03b84d7dbd5cdb3f71bfab6a249 100644 (file)
--- a/instrumentation/events/lttng-module/kmem.h
+++ b/instrumentation/events/lttng-module/kmem.h
@@ -87,6 +87,32 @@ LTTNG_TRACEPOINT_EVENT_INSTANCE(kmem_alloc_node, kmem_cache_alloc_node,
        TP_ARGS(call_site, ptr, bytes_req, bytes_alloc, gfp_flags, node)
 )
 
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,12,0))
+LTTNG_TRACEPOINT_EVENT(kfree,
+
+       TP_PROTO(unsigned long call_site, const void *ptr),
+
+       TP_ARGS(call_site, ptr),
+
+       TP_FIELDS(
+               ctf_integer_hex(unsigned long, call_site, call_site)
+               ctf_integer_hex(const void *, ptr, ptr)
+       )
+)
+
+LTTNG_TRACEPOINT_EVENT(kmem_cache_free,
+
+       TP_PROTO(unsigned long call_site, const void *ptr, const char *name),
+
+       TP_ARGS(call_site, ptr, name),
+
+       TP_FIELDS(
+               ctf_integer_hex(unsigned long, call_site, call_site)
+               ctf_integer_hex(const void *, ptr, ptr)
+               ctf_string(name, name)
+       )
+)
+#else
 LTTNG_TRACEPOINT_EVENT_CLASS(kmem_free,
 
        TP_PROTO(unsigned long call_site, const void *ptr),
@@ -114,6 +140,7 @@ LTTNG_TRACEPOINT_EVENT_INSTANCE(kmem_free, kmem_cache_free,
 
        TP_ARGS(call_site, ptr)
 )
+#endif
 
 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(3,3,0))
 LTTNG_TRACEPOINT_EVENT_MAP(mm_page_free, kmem_mm_page_free,