linux-kernel - Re: [PATCH V2 02/12] perf record: Support new sample type for data page size

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Date:   Mon, 7 Dec 2020 14:07:59 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     kan.liang@...ux.intel.com
Cc:     mingo@...nel.org, jolsa@...hat.com, linux-kernel@...r.kernel.org,
        namhyung@...nel.org, eranian@...gle.com, ak@...ux.intel.com,
        mark.rutland@....com, will@...nel.org, mpe@...erman.id.au
Subject: Re: [PATCH V2 02/12] perf record: Support new sample type for data
 page size

Em Mon, Nov 30, 2020 at 09:27:53AM -0800, kan.liang@...ux.intel.com escreveu:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> Support new sample type PERF_SAMPLE_DATA_PAGE_SIZE for page size.
> 
> Add new option --data-page-size to record sample data page size.

So, trying this on a kernel without this feature I get:

[acme@...e perf]$ perf record --data-page-size sleep 1
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cycles:u).
/bin/dmesg | grep -i perf may provide additional information.

[acme@...e perf]$

I'm adding the following patch right after yours, next time please test
this and provide a similar error message.

- Arnaldo

commit 2044fec7fcc6070b09f9b6a67922b0b9e4295dba
Author: Arnaldo Carvalho de Melo <acme@...hat.com>
Date:   Mon Dec 7 14:04:05 2020 -0300

    perf evsel: Emit warning about kernel not supporting the data page size sample_type bit
    
    Before we had this unhelpful message:
    
      $ perf record --data-page-size sleep 1
      Error:
      The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cycles:u).
      /bin/dmesg | grep -i perf may provide additional information.
      $
    
    Add support to the perf_missing_features variable to remember what
    caused evsel__open() to fail and then use that information in
    evsel__open_strerror().
    
      $ perf record --data-page-size sleep 1
      Error:
      Asking for the data page size isn't supported by this kernel.
      $
    
    Cc: Kan Liang <kan.liang@...ux.intel.com>
    Cc: Namhyung Kim <namhyung@...nel.org>
    Cc: Andi Kleen <ak@...ux.intel.com>
    Cc: Jiri Olsa <jolsa@...hat.com>
    Cc: Mark Rutland <mark.rutland@....com>
    Cc: Michael Ellerman <mpe@...erman.id.au>
    Cc: Stephane Eranian <eranian@...gle.com>
    Cc: Will Deacon <will@...nel.org>
    Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 5e6085c3fc761a55..c26ea82220bd8625 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1873,7 +1873,12 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	 * Must probe features in the order they were added to the
 	 * perf_event_attr interface.
 	 */
-        if (!perf_missing_features.cgroup && evsel->core.attr.cgroup) {
+        if (!perf_missing_features.data_page_size &&
+	    (evsel->core.attr.sample_type & PERF_SAMPLE_DATA_PAGE_SIZE)) {
+		perf_missing_features.data_page_size = true;
+		pr_debug2_peo("Kernel has no PERF_SAMPLE_DATA_PAGE_SIZE support, bailing out\n");
+		goto out_close;
+	} else if (!perf_missing_features.cgroup && evsel->core.attr.cgroup) {
 		perf_missing_features.cgroup = true;
 		pr_debug2_peo("Kernel has no cgroup sampling support, bailing out\n");
 		goto out_close;
@@ -2673,6 +2678,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 	"We found oprofile daemon running, please stop it and try again.");
 		break;
 	case EINVAL:
+		if (evsel->core.attr.sample_type & PERF_SAMPLE_DATA_PAGE_SIZE && perf_missing_features.data_page_size)
+			return scnprintf(msg, size, "Asking for the data page size isn't supported by this kernel.");
 		if (evsel->core.attr.write_backward && perf_missing_features.write_backward)
 			return scnprintf(msg, size, "Reading from overwrite event is not supported by this kernel.");
 		if (perf_missing_features.clockid)
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 79a860d8e3eefe23..cd1d8dd431997b84 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -144,6 +144,7 @@ struct perf_missing_features {
 	bool aux_output;
 	bool branch_hw_idx;
 	bool cgroup;
+	bool data_page_size;
 };
 
 extern struct perf_missing_features perf_missing_features;