Re: [PATCH v1 01/16] perf header: Make nodes dynamic in write_mem_topology

[Ian Rogers <irogers@google.com>]

On Thu, May 25, 2023 at 12:15 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Thu, May 25, 2023 at 12:12 AM Ian Rogers <irogers@google.com> wrote:
> >
> > Avoid a large static array, dynamically allocate the nodes avoiding a
> > hard coded limited as well.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/perf/util/header.c | 33 +++++++++++++++++++++------------
> >  1 file changed, 21 insertions(+), 12 deletions(-)
> >
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index 2dde3ca20de5..80593ed8c79b 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -24,6 +24,7 @@
> >  #include <bpf/libbpf.h>
> >  #endif
> >  #include <perf/cpumap.h>
> > +#include <tools/libc_compat.h> // reallocarray
> >
> >  #include "dso.h"
> >  #include "evlist.h"
> > @@ -1396,13 +1397,14 @@ static int memory_node__sort(const void *a, const void *b)
> >         return na->node - nb->node;
> >  }
> >
> > -static int build_mem_topology(struct memory_node *nodes, u64 size, u64 *cntp)
> > +static int build_mem_topology(struct memory_node **nodesp, u64 *cntp)
> >  {
> >         char path[PATH_MAX];
> >         struct dirent *ent;
> >         DIR *dir;
> > -       u64 cnt = 0;
> >         int ret = 0;
> > +       size_t cnt = 0, size = 0;
> > +       struct memory_node *nodes = NULL;
> >
> >         scnprintf(path, PATH_MAX, "%s/devices/system/node/",
> >                   sysfs__mountpoint());
> > @@ -1426,16 +1428,24 @@ static int build_mem_topology(struct memory_node *nodes, u64 size, u64 *cntp)
> >                 if (r != 1)
> >                         continue;
> >
> > -               if (WARN_ONCE(cnt >= size,
> > -                       "failed to write MEM_TOPOLOGY, way too many nodes\n")) {
> > -                       closedir(dir);
> > -                       return -1;
> > -               }
> > +               if (cnt >= size) {
> > +                       struct memory_node *new_nodes =
> > +                               reallocarray(nodes, cnt + 4, sizeof(*nodes));
> >
> > +                       if (!new_nodes) {
> > +                               pr_err("Failed to write MEM_TOPOLOGY, size %zd nodes\n", size);
> > +                               free(nodes);
> > +                               closedir(dir);
> > +                               return -ENOMEM;
> > +                       }
> > +                       nodes = new_nodes;
> > +                       size += 4;
> > +               }
> >                 ret = memory_node__read(&nodes[cnt++], idx);
>
> I think you need to handle error cases here.
>
> Thanks,
> Namhyung

Not sure I follow. The reallocarray tests for failure, frees nodes and
returns -ENOMEM on error.

Thanks,
Ian

>
> >         }
> >
> >         *cntp = cnt;
> > +       *nodesp = nodes;
> >         closedir(dir);
> >
> >         if (!ret)
> > @@ -1444,8 +1454,6 @@ static int build_mem_topology(struct memory_node *nodes, u64 size, u64 *cntp)
> >         return ret;
> >  }
> >
> > -#define MAX_MEMORY_NODES 2000
> > -
> >  /*
> >   * The MEM_TOPOLOGY holds physical memory map for every
> >   * node in system. The format of data is as follows:
> > @@ -1464,8 +1472,8 @@ static int build_mem_topology(struct memory_node *nodes, u64 size, u64 *cntp)
> >  static int write_mem_topology(struct feat_fd *ff __maybe_unused,
> >                               struct evlist *evlist __maybe_unused)
> >  {
> > -       static struct memory_node nodes[MAX_MEMORY_NODES];
> > -       u64 bsize, version = 1, i, nr;
> > +       struct memory_node *nodes = NULL;
> > +       u64 bsize, version = 1, i, nr = 0;
> >         int ret;
> >
> >         ret = sysfs__read_xll("devices/system/memory/block_size_bytes",
> > @@ -1473,7 +1481,7 @@ static int write_mem_topology(struct feat_fd *ff __maybe_unused,
> >         if (ret)
> >                 return ret;
> >
> > -       ret = build_mem_topology(&nodes[0], MAX_MEMORY_NODES, &nr);
> > +       ret = build_mem_topology(&nodes, &nr);
> >         if (ret)
> >                 return ret;
> >
> > @@ -1508,6 +1516,7 @@ static int write_mem_topology(struct feat_fd *ff __maybe_unused,
> >         }
> >
> >  out:
> > +       free(nodes);
> >         return ret;
> >  }
> >
> > --
> > 2.40.1.698.g37aff9b760-goog
> >