linux-kernel - Re: [PATCH] perf script: Fix Cannot print 'iregs' field for hybrid systems

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Date:   Thu, 8 Sep 2022 10:24:27 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     zhengjun.xing@...ux.intel.com
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...el.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        irogers@...gle.com, ak@...ux.intel.com, kan.liang@...ux.intel.com
Subject: Re: [PATCH] perf script: Fix Cannot print 'iregs' field for hybrid
 systems

On Thu, Sep 08, 2022 at 03:00:30PM +0800, zhengjun.xing@...ux.intel.com wrote:
> From: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> 
> Commit b91e5492f9d7 ("perf record: Add a dummy event on hybrid systems to
> collect metadata records") adds a dummy event on hybrid systems to fix the
> symbol "unknown" issue when the workload is created in a P-core but runs
> on an E-core. The added dummy event will cause "perf script -F iregs" to
> fail. Dummy events do not have "iregs" attribute set, so when we do
> evsel__check_attr, the "iregs" attribute check will fail, so the issue
> happened.
> 
> The following commit [1] has fixed a similar issue by skipping the attr
> check for the dummy event because it does not have any samples anyway. It
> works okay for the normal mode, but the issue still happened when running
> the test in the pipe mode. In the pipe mode, it calls process_attr() which
> still checks the attr for the dummy event. This commit fixed the issue by
> skipping the attr check for the dummy event in the API evsel__check_attr,
> Otherwise, we have to patch everywhere when evsel__check_attr() is called.
> 
> Before:
> 
>  #./perf record -o - --intr-regs=di,r8,dx,cx -e br_inst_retired.near_call:p -c 1000 --per-thread true 2>/dev/null|./perf script -F iregs |head -5
> Samples for 'dummy:HG' event do not have IREGS attribute set. Cannot print 'iregs' field.
> 0x120 [0x90]: failed to process type: 64
> 
> After:
> 
>  # ./perf record -o - --intr-regs=di,r8,dx,cx -e br_inst_retired.near_call:p -c 1000 --per-thread true 2>/dev/null|./perf script -F iregs |head -5
>  ABI:2    CX:0x55b8efa87000    DX:0x55b8efa7e000    DI:0xffffba5e625efbb0    R8:0xffff90e51f8ae100
>  ABI:2    CX:0x7f1dae1e4000    DX:0xd0    DI:0xffff90e18c675ac0    R8:0x71
>  ABI:2    CX:0xcc0    DX:0x1    DI:0xffff90e199880240    R8:0x0
>  ABI:2    CX:0xffff90e180dd7500    DX:0xffff90e180dd7500    DI:0xffff90e180043500    R8:0x1
>  ABI:2    CX:0x50    DX:0xffff90e18c583bd0    DI:0xffff90e1998803c0    R8:0x58
> 
> [1]https://lore.kernel.org/lkml/20220831124041.219925-1-jolsa@kernel.org/
> 
> Fixes: b91e5492f9d7 ("perf record: Add a dummy event on hybrid systems to collect metadata records")
> 
> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> Suggested-by: Namhyung Kim <namhyung@...nel.org>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka

> ---
>  tools/perf/builtin-script.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index 585171479876..1a8790385eba 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -445,6 +445,9 @@ static int evsel__check_attr(struct evsel *evsel, struct perf_session *session)
>  	struct perf_event_attr *attr = &evsel->core.attr;
>  	bool allow_user_set;
>  
> +	if (evsel__is_dummy_event(evsel))
> +		return 0;
> +
>  	if (perf_header__has_feat(&session->header, HEADER_STAT))
>  		return 0;
>  
> -- 
> 2.25.1
>