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perf expr: Migrate expr ids table to a hashmap

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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>
This commit is contained in:
Ian Rogers
2020-05-15 15:17:32 -07:00
committed by Arnaldo Carvalho de Melo
parent eee1950192
commit ded80bda8b
7 changed files with 200 additions and 190 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
tools/perf/util/expr.y
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@@ -47,19 +47,6 @@ static void expr_error(double *final_val __maybe_unused,
pr_debug("%s\n", s);
}
static int lookup_id(struct expr_parse_ctx *ctx, char *id, double *val)
{
int i;
for (i = 0; i < ctx->num_ids; i++) {
if (!strcasecmp(ctx->ids[i].name, id)) {
*val = ctx->ids[i].val;
return 0;
}
}
return -1;
}
%}
%%
@@ -73,12 +60,7 @@ all_other: all_other other
other: ID
{
if (ctx->num_ids + 1 >= EXPR_MAX_OTHER) {
pr_err("failed: way too many variables");
YYABORT;
}
ctx->ids[ctx->num_ids++].name = $1;
expr__add_id(ctx, $1, 0.0);
}
|
MIN | MAX | IF | ELSE | SMT_ON | NUMBER | '|' | '^' | '&' | '-' | '+' | '*' | '/' | '%' | '(' | ')' | ','
@@ -93,7 +75,7 @@ if_expr:
;
expr: NUMBER
| ID { if (lookup_id(ctx, $1, &$$) < 0) {
| ID { if (expr__get_id(ctx, $1, &$$)) {
pr_debug("%s not found\n", $1);
free($1);
YYABORT;