[PATCH] bpf: Allocate bpf_event_entry with node info

[PATCH] bpf: Allocate bpf_event_entry with node info

[Namhyung Kim]

It was reported that accessing perf_event map entry caused pretty high
LLC misses in get_map_perf_counter().  As reading perf_event is allowed
for the local CPU only, I think we can use the target CPU of the event
as hint for the allocation like in perf_event_alloc() so that the event
and the entry can be in the same node at least.

Reported-by: Aleksei Shchekotikhin <alekseis@google.com>
Reported-by: Nilay Vaish <nilayvaish@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/bpf/arraymap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index feabc0193852..3f7718c261d7 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -1194,10 +1194,15 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
 						   struct file *map_file)
 {
 	struct bpf_event_entry *ee;
+	struct perf_event *event = perf_file->private_data;
+	int node = -1;
 
-	ee = kzalloc(sizeof(*ee), GFP_KERNEL);
+	if (event->cpu >= 0)
+		node = cpu_to_node(cpu);
+
+	ee = kzalloc_node(sizeof(*ee), GFP_KERNEL, node);
 	if (ee) {
-		ee->event = perf_file->private_data;
+		ee->event = event;
 		ee->perf_file = perf_file;
 		ee->map_file = map_file;
 	}
-- 
2.45.1.288.g0e0cd299f1-goog

Re: [PATCH] bpf: Allocate bpf_event_entry with node info

[kernel test robot]

Hi Namhyung,

kernel test robot noticed the following build errors:

[auto build test ERROR on bpf-next/master]
[also build test ERROR on bpf/master linus/master v6.10-rc1 next-20240528]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Namhyung-Kim/bpf-Allocate-bpf_event_entry-with-node-info/20240529-063828
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20240528223643.1166776-1-namhyung%40kernel.org
patch subject: [PATCH] bpf: Allocate bpf_event_entry with node info
config: m68k-defconfig (https://download.01.org/0day-ci/archive/20240529/202405291415.6JlTkRMF-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240529/202405291415.6JlTkRMF-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202405291415.6JlTkRMF-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

   kernel/bpf/arraymap.c: In function 'bpf_event_entry_gen':
>> kernel/bpf/arraymap.c:1200:18: error: 'struct perf_event' has no member named 'cpu'
    1200 |         if (event->cpu >= 0)
         |                  ^~
   In file included from ./arch/m68k/include/generated/asm/topology.h:1,
                    from include/linux/topology.h:36,
                    from include/linux/gfp.h:8,
                    from include/linux/umh.h:4,
                    from include/linux/kmod.h:9,
                    from include/linux/module.h:17,
                    from include/linux/bpf.h:20,
                    from kernel/bpf/arraymap.c:5:
   kernel/bpf/arraymap.c:1201:36: error: 'cpu' undeclared (first use in this function)
    1201 |                 node = cpu_to_node(cpu);
         |                                    ^~~
   include/asm-generic/topology.h:35:41: note: in definition of macro 'cpu_to_node'
      35 | #define cpu_to_node(cpu)        ((void)(cpu),0)
         |                                         ^~~
   kernel/bpf/arraymap.c:1201:36: note: each undeclared identifier is reported only once for each function it appears in
    1201 |                 node = cpu_to_node(cpu);
         |                                    ^~~
   include/asm-generic/topology.h:35:41: note: in definition of macro 'cpu_to_node'
      35 | #define cpu_to_node(cpu)        ((void)(cpu),0)
         |                                         ^~~
>> include/asm-generic/topology.h:35:45: warning: left-hand operand of comma expression has no effect [-Wunused-value]
      35 | #define cpu_to_node(cpu)        ((void)(cpu),0)
         |                                             ^
   kernel/bpf/arraymap.c:1201:24: note: in expansion of macro 'cpu_to_node'
    1201 |                 node = cpu_to_node(cpu);
         |                        ^~~~~~~~~~~


vim +1200 kernel/bpf/arraymap.c

  1192	
  1193	static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
  1194							   struct file *map_file)
  1195	{
  1196		struct bpf_event_entry *ee;
  1197		struct perf_event *event = perf_file->private_data;
  1198		int node = -1;
  1199	
> 1200		if (event->cpu >= 0)
  1201			node = cpu_to_node(cpu);
  1202	
  1203		ee = kzalloc_node(sizeof(*ee), GFP_KERNEL, node);
  1204		if (ee) {
  1205			ee->event = event;
  1206			ee->perf_file = perf_file;
  1207			ee->map_file = map_file;
  1208		}
  1209	
  1210		return ee;
  1211	}
  1212	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki