Re: [PATCH v2 0/7] Share events between metrics

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>, Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Song Liu <songliubraving@fb.com>,
	Andrii Nakryiko <andriin@fb.com>,
	Kajol Jain <kjain@linux.ibm.com>, Andi Kleen <ak@linux.intel.com>,
	John Garry <john.garry@huawei.com>,
	Jin Yao <yao.jin@linux.intel.com>,
	Kan Liang <kan.liang@linux.intel.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Kim Phillips <kim.phillips@amd.com>, Paul Clarke <pc@us.ibm.com>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, linux-perf-users@vger.kernel.org,
	Vince Weaver <vincent.weaver@maine.edu>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH v2 0/7] Share events between metrics
Date: Fri, 22 May 2020 11:49:08 -0300	[thread overview]
Message-ID: <20200522144908.GI14034@kernel.org> (raw)
In-Reply-To: <20200522101311.GA404187@krava>

Em Fri, May 22, 2020 at 12:13:11PM +0200, Jiri Olsa escreveu:
> On Thu, May 21, 2020 at 02:22:35PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, May 21, 2020 at 01:43:25PM +0200, Jiri Olsa escreveu:
> > > On Wed, May 20, 2020 at 11:20:04AM -0700, Ian Rogers wrote:
> > > 
> > > SNIP
> > > 
> > > > There are 5 out of 12 metric groups where no events are shared, such
> > > > as Power, however, disabling grouping of events always reduces the
> > > > number of events.
> > > > 
> > > > The result for Memory_BW needs explanation:
> > > > 
> > > > Metric group: Memory_BW
> > > >  - No merging (old default, now --metric-no-merge): 9
> > > >  - Merging over metrics (new default)             : 5
> > > >  - No event groups and merging (--metric-no-group): 11
> > > > 
> > > > Both with and without merging the groups fail to be set up and so the
> > > > event counts here are for broken metrics. The --metric-no-group number
> > > > is accurate as all the events are scheduled. Ideally a constraint
> > > > would be added for these metrics in the json code to avoid grouping.
> > > > 
> > > > v2. rebases on kernel/git/acme/linux.git branch tmp.perf/core, fixes a
> > > > missing comma with metric lists (reported-by Jiri Olsa
> > > > <jolsa@redhat.com>) and adds early returns to metricgroup__add_metric
> > > > (suggested-by Jiri Olsa).
> > > 
> > > Acked-by: Jiri Olsa <jolsa@redhat.com>
> > 
> > Applied and pushed to tmp.perf/core, will move to perf/core as soon as
> > testing finishes,
> 
> I checked tmp.perf/core and I'm getting segfault for 'perf test expr'

Right, reproduced here and...

> 	 7: Simple expression parser                              :
> 	Program received signal SIGSEGV, Segmentation fault.
> 	0x000000000067841e in hashmap_find_entry (map=0x7fffffffd0c0, key=0xc83b30, hash=9893851511679796638, pprev=0x0, entry=0x7fffffffc658) at hashmap.c:131
> 	131             for (prev_ptr = &map->buckets[hash], cur = *prev_ptr;
> 	(gdb) bt
> 	#0  0x000000000067841e in hashmap_find_entry (map=0x7fffffffd0c0, key=0xc83b30, hash=9893851511679796638, pprev=0x0, entry=0x7fffffffc658) at hashmap.c:131
> 	#1  0x000000000067853a in hashmap__insert (map=0x7fffffffd0c0, key=0xc83b30, value=0x0, strategy=HASHMAP_SET, old_key=0x7fffffffc718, 
> 	    old_value=0x7fffffffc710) at hashmap.c:160
> 	#2  0x00000000005d3209 in hashmap__set (map=0x7fffffffd0c0, key=0xc83b30, value=0x0, old_key=0x7fffffffc718, old_value=0x7fffffffc710)
> 	    at /home/jolsa/kernel/linux-perf/tools/perf/util/hashmap.h:107
> 	#3  0x00000000005d3386 in expr__add_id (ctx=0x7fffffffd0c0, name=0xc83b30 "FOO", val=0) at util/expr.c:45
> 	#4  0x00000000005d27ee in expr_parse (final_val=0x0, ctx=0x7fffffffd0c0, scanner=0xc87990) at util/expr.y:63
> 	#5  0x00000000005d35b7 in __expr__parse (val=0x0, ctx=0x7fffffffd0c0, expr=0x75a84b "FOO + BAR + BAZ + BOZO", start=259, runtime=1) at util/expr.c:102
> 	#6  0x00000000005d36c6 in expr__find_other (expr=0x75a84b "FOO + BAR + BAZ + BOZO", one=0x75a791 "FOO", ctx=0x7fffffffd0c0, runtime=1) at util/expr.c:121
> 	#7  0x00000000004e3aaf in test__expr (t=0xa7bd40 <generic_tests+384>, subtest=-1) at tests/expr.c:55
> 	#8  0x00000000004b5651 in run_test (test=0xa7bd40 <generic_tests+384>, subtest=-1) at tests/builtin-test.c:393
> 	#9  0x00000000004b5787 in test_and_print (t=0xa7bd40 <generic_tests+384>, force_skip=false, subtest=-1) at tests/builtin-test.c:423
> 	#10 0x00000000004b61c4 in __cmd_test (argc=1, argv=0x7fffffffd7f0, skiplist=0x0) at tests/builtin-test.c:628
> 	#11 0x00000000004b6911 in cmd_test (argc=1, argv=0x7fffffffd7f0) at tests/builtin-test.c:772
> 	#12 0x00000000004e977b in run_builtin (p=0xa7eee8 <commands+552>, argc=3, argv=0x7fffffffd7f0) at perf.c:312
> 	#13 0x00000000004e99e8 in handle_internal_command (argc=3, argv=0x7fffffffd7f0) at perf.c:364
> 	#14 0x00000000004e9b2f in run_argv (argcp=0x7fffffffd64c, argv=0x7fffffffd640) at perf.c:408
> 	#15 0x00000000004e9efb in main (argc=3, argv=0x7fffffffd7f0) at perf.c:538
> 
> attached patch fixes it for me, but I'm not sure this
> should be necessary

... applying the patch below makes the segfault go away. Ian, Ack? I can
fold it into the patch introducing the problem.

- Arnaldo

> jirka
> 
> 
> ---
> diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
> index 1cb02ca2b15f..21693fe516c1 100644
> --- a/tools/perf/tests/expr.c
> +++ b/tools/perf/tests/expr.c
> @@ -52,6 +52,7 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
>  	TEST_ASSERT_VAL("missing operand", ret == -1);
>  
>  	expr__ctx_clear(&ctx);
> +	expr__ctx_init(&ctx);
>  	TEST_ASSERT_VAL("find other",
>  			expr__find_other("FOO + BAR + BAZ + BOZO", "FOO",
>  					 &ctx, 1) == 0);
> @@ -64,6 +65,7 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
>  						    (void **)&val_ptr));
>  
>  	expr__ctx_clear(&ctx);
> +	expr__ctx_init(&ctx);
>  	TEST_ASSERT_VAL("find other",
>  			expr__find_other("EVENT1\\,param\\=?@ + EVENT2\\,param\\=?@",
>  					 NULL, &ctx, 3) == 0);
> 
> 

-- 

- Arnaldo