perf expr: Migrate expr ids table to a hashmap

Use a hashmap between a char* string and a double* value. While bpf's
hashmap entries are size_t in size, we can't guarantee sizeof(size_t) >=
sizeof(double). Avoid a memory allocation when gathering ids by making
0.0 a special value encoded as NULL.

Original map suggestion by Andi Kleen:

  https://lore.kernel.org/lkml/20200224210308.GQ160988@tassilo.jf.intel.com/

and seconded by Jiri Olsa:

  https://lore.kernel.org/lkml/20200423112915.GH1136647@krava/

Committer notes:

There are fixes that need to land upstream before we can use libbpf's
headers, for now use our copy unconditionally, since the data structures
at this point are exactly the same, no problem.

When the fixes for libbpf's hashmap land upstream, we can fix this up.

Testing it:

Building with LIBBPF=1, i.e. the default:

  $ perf -vv | grep -i bpf
                     bpf: [ on  ]  # HAVE_LIBBPF_SUPPORT
  $ nm ~/bin/perf | grep -i libbpf_ | wc -l
  39
  $ nm ~/bin/perf | grep -i hashmap_ | wc -l
  17
  $

Explicitely building without LIBBPF:

  $ perf -vv | grep -i bpf
                     bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
  $
  $ nm ~/bin/perf | grep -i libbpf_ | wc -l
  0
  $ nm ~/bin/perf | grep -i hashmap_ | wc -l
  9
  $

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: kp singh <kpsingh@chromium.org>
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200515221732.44078-8-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index 40fc452b0f2b..8a2c1074f90f 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -2,17 +2,17 @@
 #ifndef PARSE_CTX_H
 #define PARSE_CTX_H 1
 
-#define EXPR_MAX_OTHER 64
-#define MAX_PARSE_ID EXPR_MAX_OTHER
-
-struct expr_parse_id {
-	const char *name;
-	double val;
-};
+// There are fixes that need to land upstream before we can use libbpf's headers,
+// for now use our copy uncoditionally, since the data structures at this point
+// are exactly the same, no problem.
+//#ifdef HAVE_LIBBPF_SUPPORT
+//#include <bpf/hashmap.h>
+//#else
+#include "util/hashmap.h"
+//#endif
 
 struct expr_parse_ctx {
-	int num_ids;
-	struct expr_parse_id ids[MAX_PARSE_ID];
+	struct hashmap ids;
 };
 
 struct expr_scanner_ctx {
@@ -21,9 +21,12 @@ struct expr_scanner_ctx {
 };
 
 void expr__ctx_init(struct expr_parse_ctx *ctx);
-void expr__add_id(struct expr_parse_ctx *ctx, const char *id, double val);
-int expr__parse(double *final_val, struct expr_parse_ctx *ctx, const char *expr, int runtime);
-int expr__find_other(const char *expr, const char *one, const char ***other,
-		int *num_other, int runtime);
+void expr__ctx_clear(struct expr_parse_ctx *ctx);
+int expr__add_id(struct expr_parse_ctx *ctx, const char *id, double val);
+int expr__get_id(struct expr_parse_ctx *ctx, const char *id, double *val_ptr);
+int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
+		const char *expr, int runtime);
+int expr__find_other(const char *expr, const char *one,
+		struct expr_parse_ctx *ids, int runtime);
 
 #endif