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

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Date:   Thu, 8 Sep 2022 15:28:33 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     zhengjun.xing@...ux.intel.com, 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

Em Thu, Sep 08, 2022 at 10:24:27AM +0200, Jiri Olsa escreveu:
> 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, applied.

- Arnaldo