Re: [PATCH v9 2/9] perf c2c: add function view model skeleton

[Ian Rogers]

On Mon, Aug 17, 2026 at 3:48 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Mon, Aug 17, 2026 at 01:53:46PM -0700, Ian Rogers wrote:
> > On Mon, Aug 17, 2026 at 2:40 AM Jiebin Sun <jiebin.sun@xxxxxxxxx> wrote:
> > >
> > > Add the initial common model for the c2c function view: model state and
> > > small helpers shared by the hierarchy construction and formatting added
> > > in later patches.
> > >
> > > Build the model from util/ so it remains independent of the TUI and
> > > command-private symbols.
> > >
> > > Signed-off-by: Jiebin Sun <jiebin.sun@xxxxxxxxx>
> > > Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> > > Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> > > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > > Cc: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
> > > Cc: Ian Rogers <irogers@xxxxxxxxxx>
> > > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > > Cc: James Clark <james.clark@xxxxxxxxxx>
> > > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > > Cc: Thomas Falcon <thomas.falcon@xxxxxxxxx>
> > > Reviewed-by: Tianyou Li <tianyou.li@xxxxxxxxx>
> > > Reviewed-by: Wangyang Guo <wangyang.guo@xxxxxxxxx>
> > > ---
> > >  tools/perf/util/Build          |  1 +
> > >  tools/perf/util/c2c-function.c | 66 ++++++++++++++++++++++++++++++++++
> > >  2 files changed, 67 insertions(+)
> > >  create mode 100644 tools/perf/util/c2c-function.c
> > >
> > > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > > index 1dfd92cbe3b7..b26a0b1ddfa3 100644
> > > --- a/tools/perf/util/Build
> > > +++ b/tools/perf/util/Build
> > > @@ -12,6 +12,7 @@ perf-util-y += block-info.o
> > >  perf-util-y += block-range.o
> > >  perf-util-y += build-id.o
> > >  perf-util-y += c2c.o
> > > +perf-util-y += c2c-function.o
> > >  perf-util-y += cacheline.o
> > >  perf-util-$(CONFIG_LIBCAPSTONE) += capstone.o
> > >  perf-util-y += config.o
> > > diff --git a/tools/perf/util/c2c-function.c b/tools/perf/util/c2c-function.c
> > > new file mode 100644
> > > index 000000000000..ca82425a28dc
> > > --- /dev/null
> > > +++ b/tools/perf/util/c2c-function.c
> > > @@ -0,0 +1,66 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * C2C function model - function-level cacheline sharing analysis
> > > + *
> > > + * Displays a 3-level hierarchy showing which functions share cachelines:
> > > + *   Level 1: Read-side functions sorted by Cycles % (estimated load cycles)
> > > + *   Level 2: Functions sampled writing the shared lines read by level 1
> > > + *   Level 3: The specific cachelines where the two functions contend
> > > + *
> > > + * Builds the hierarchy from the existing cacheline histograms
> > > + * (c2c_hist_entry->hists), reusing the shared c2c data structures.
> > > + */
> > > +
> > > +#include <errno.h>
> > > +#include <inttypes.h>
> > > +#include <stdlib.h>
> > > +#include <string.h>
> > > +#include <tools/libc_compat.h> /* reallocarray */
> > > +#include <linux/list.h>
> > > +#include <linux/rbtree.h>
> > > +#include <linux/zalloc.h>
> > > +
> > > +#include "addr_location.h"
> > > +#include "c2c.h"
> > > +#include "cacheline.h"
> > > +#include "hist.h"
> > > +#include "map.h"
> > > +#include "mem-events.h"
> > > +#include "mem-info.h"
> > > +#include "sort.h"
> > > +#include "symbol.h"
> > > +#include "thread.h"
> >
> > nit: the number of #includes is somewhat generous here. I presume
> > later patches will require these includes. To avoid everything
> > depending on everything else it would be nice to use forward
> > declarations when possible. For example, if the only reason for
> > including the header file was to use a struct's name where it is
> > passed as a pointer in a function declaration, ie in header files
> > prefer:
> >
> >   struct map;
> >   int foo(struct map *m);
> >
> > over
> >
> >   #include "map.h"
> >   int foo(struct map *m);
>
> I think they are actually used in the later patches in this series.

Ah. I misread and thought they were being added to the header file. My
mistake and I guess it is okay to add unused header file #includes in
the same way as the patches introduce initially unused functions.

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> >
> > > +
> > > +struct c2c_function_model {
> > > +       struct c2c_hists        function_hists;
> > > +       /* Total estimated cycles across all level-1 entries. */
> > > +       u64                     total_cycles;
> > > +       /* Source cacheline histograms; not owned here. */
> > > +       struct c2c_hists        *cl_hists;
> > > +       /* --coalesce field list, used to require iaddr. */
> > > +       const char              *cl_sort;
> > > +       /* Do not cap long symbol names. */
> > > +       bool                     symbol_full;
> > > +};
> > > +
> > > +static struct c2c_function_model c2c_ext __maybe_unused;
> > > +
> > > +static inline __maybe_unused u64 c2c_hitm_count(const struct c2c_stats *stats)
> > > +{
> > > +       return stats->tot_hitm;
> > > +}
> > > +
> > > +static inline __maybe_unused bool symbol_name_equal(struct symbol *a, struct symbol *b)
> > > +{
> > > +       /* Two unknown symbols compare equal, matching cmp_null() in util/sort.c. */
> > > +       if (!a || !b)
> > > +               return a == b;
> > > +       return arch__compare_symbol_names(a->name, b->name) == 0;
> >
> > Sashiko rightly flagged this as not being cross-platform compatible,
> > but this is a pre-existing issue that looks relatively easy to clean
> > up but only really impacts PowerPC and so is hard for me to test. I'll
> > try to do it anyway.
>
> Thanks for your review.  Yep, I think it can be handled separately.
>
> Namhyung
>
> >
> > > +}
> > > +
> > > +static inline __maybe_unused u64 hist_entry__iaddr(struct hist_entry *he)
> > > +{
> > > +       if (he->mem_info)
> > > +               return mem_info__iaddr(he->mem_info)->addr;
> > > +       return he->ip;
> > > +}
> > > --
> > > 2.52.0
> > >