linux-kernel - Re: [PATCH] perf mem: Fix printing PERF_MEM_LVLNUM_{L2

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Message-ID: <3bb83817d36128426cafa31b6cd5863be89f1ea0.camel@intel.com>
Date: Wed, 25 Sep 2024 21:40:15 +0000
From: "Falcon, Thomas" <thomas.falcon@...el.com>
To: "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
	"leo.yan@....com" <leo.yan@....com>, "peterz@...radead.org"
	<peterz@...radead.org>, "acme@...nel.org" <acme@...nel.org>,
	"mingo@...hat.com" <mingo@...hat.com>, "mark.rutland@....com"
	<mark.rutland@....com>, "Hunter, Adrian" <adrian.hunter@...el.com>,
	"namhyung@...nel.org" <namhyung@...nel.org>, "jolsa@...nel.org"
	<jolsa@...nel.org>, "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
	"irogers@...gle.com" <irogers@...gle.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH] perf mem: Fix printing PERF_MEM_LVLNUM_{L2_MHB|MSC}

On Wed, 2024-09-25 at 21:16 +0100, Leo Yan wrote:
> On 9/25/2024 7:36 PM, Thomas Falcon wrote:
> > 
> > 
> > With commit 8ec9497d3ef34 ("tools/include: Sync uapi/linux/perf.h
> > with the kernel sources"), 'perf mem report' gives an incorrect
> > memory
> > access string.
> > ...
> > 0.02%   1       3644    L5 hit  [.] 0x0000000000009b0e  mlc     [.]
> > 0x00007fce43f59480
> > ...
> > 
> > This occurs because, if no entry exists in mem_lvlnum,
> > perf_mem__lvl_scnprintf
> > will default to 'L%d, lvl', which in this case for
> > PERF_MEM_LVLNUM_L2_MHB is 0x05.
> > Add entries for PERF_MEM_LVLNUM_L2_MHB and PERF_MEM_LVLNUM_MSC to
> > mem_lvlnum,
> > so that the correct strings are printed.
> > ...
> > 0.02%   1       3644    L2 MHB hit      [.] 0x0000000000009b0e 
> > mlc     [.] 0x00007fce43f59480
> > ...
> > 
> > Fixes: 8ec9497d3ef34 ("tools/include: Sync uapi/linux/perf.h with
> > the kernel sources")
> > Suggested-by: Kan Liang <kan.liang@...ux.intel.com>
> > Signed-off-by: Thomas Falcon <thomas.falcon@...el.com>
> > Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
> 
> This change is fine for me. But for later avoid same issues, I would
> like to
> improve a bit:
> 
> static const char * const mem_lvlnum[] = {
>        [PERF_MEM_LVLNUM_L1] = "L1",
>        [PERF_MEM_LVLNUM_L2] = "L2",
>        [PERF_MEM_LVLNUM_L3] = "L3",
>        [PERF_MEM_LVLNUM_L4] = "L4",
>        [PERF_MEM_LVLNUM_L2_MHB] = "L2 MHB",
>        [PERF_MEM_LVLNUM_MSC] = "Memory-side Cache",
>        ...
> };
> 
> Then in the function perf_mem__lvl_scnprintf() :
> 
>    if (mem_lvlnum[lvl])
>        l += scnprintf(out + l, sz - l, mem_lvlnum[lvl]);
>    else
>        l += scnprintf(out + l, sz - l, "Unknown level %d", lvl);
> 
> This can help us easily to catch unexpected memory level.
> 

Thank you! I will send an updated v2 with your suggested changes. 

Tom

> Thanks,
> Leo
> 
> > ---
> >  tools/perf/util/mem-events.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-
> > events.c
> > index 051feb93ed8d..c630aca5bd93 100644
> > --- a/tools/perf/util/mem-events.c
> > +++ b/tools/perf/util/mem-events.c
> > @@ -366,6 +366,8 @@ static const char * const mem_lvl[] = {
> >  };
> > 
> >  static const char * const mem_lvlnum[] = {
> > +       [PERF_MEM_LVLNUM_L2_MHB] = "L2 MHB",
> > +       [PERF_MEM_LVLNUM_MSC] = "Memory-side Cache",
> >         [PERF_MEM_LVLNUM_UNC] = "Uncached",
> >         [PERF_MEM_LVLNUM_CXL] = "CXL",
> >         [PERF_MEM_LVLNUM_IO] = "I/O",
> > --
> > 2.46.0
> > 
> >