perf header: Fix false warning when there are no duplicate cache entries

Before this patch, perf expected that there might be NPROC*4 unique
cache entries at max, however, it also expected that some of them would
be shared and/or of the same size, thus the final number of entries
would be reduced to be lower than NPROC*4. In case the number of entries
hadn't been reduced (was NPROC*4), the warning was printed.

However, some systems might have unusual cache topology, such as the
following two-processor KVM guest:

	cpu  level  shared_cpu_list  size
	  0     1         0           32K
	  0     1         0           64K
	  0     2         0           512K
	  0     3         0           8192K
	  1     1         1           32K
	  1     1         1           64K
	  1     2         1           512K
	  1     3         1           8192K

This KVM guest has 8 (NPROC*4) unique cache entries, which used to make
perf printing the message, although there actually aren't "way too many
cpu caches".

v2: Removing unused argument.

v3: Unifying the way we obtain number of cpus.

v4: Removed '& UINT_MAX' construct which is redundant.

Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
LPU-Reference: 20191208162056.20772-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 4d39a75551a0b4f56522ecf579225886d1565e15..93ad27830e2bdf7fa2758c53c98b3a95ba167de9 100644 (file)
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1089,21 +1089,18 @@ static void cpu_cache_level__fprintf(FILE *out, struct cpu_cache_level *c)
        fprintf(out, "L%d %-15s %8s [%s]\n", c->level, c->type, c->size, c->map);
 }
 
-static int build_caches(struct cpu_cache_level caches[], u32 size, u32 *cntp)
+#define MAX_CACHE_LVL 4
+
+static int build_caches(struct cpu_cache_level caches[], u32 *cntp)
 {
        u32 i, cnt = 0;
-       long ncpus;
        u32 nr, cpu;
        u16 level;
 
-       ncpus = sysconf(_SC_NPROCESSORS_CONF);
-       if (ncpus < 0)
-               return -1;
-
-       nr = (u32)(ncpus & UINT_MAX);
+       nr = cpu__max_cpu();
 
        for (cpu = 0; cpu < nr; cpu++) {
-               for (level = 0; level < 10; level++) {
+               for (level = 0; level < MAX_CACHE_LVL; level++) {
                        struct cpu_cache_level c;
                        int err;
 
@@ -1123,18 +1120,12 @@ static int build_caches(struct cpu_cache_level caches[], u32 size, u32 *cntp)
                                caches[cnt++] = c;
                        else
                                cpu_cache_level__free(&c);
-
-                       if (WARN_ONCE(cnt == size, "way too many cpu caches.."))
-                               goto out;
                }
        }
- out:
        *cntp = cnt;
        return 0;
 }
 
-#define MAX_CACHE_LVL 4
-
 static int write_cache(struct feat_fd *ff,
                       struct evlist *evlist __maybe_unused)
 {
@@ -1143,7 +1134,7 @@ static int write_cache(struct feat_fd *ff,
        u32 cnt = 0, i, version = 1;
        int ret;
 
-       ret = build_caches(caches, max_caches, &cnt);
+       ret = build_caches(caches, &cnt);
        if (ret)
                goto out;