linux-kernel - Re: [PATCH v1 01/16] perf header: Make nodes dynamic in write_mem

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Message-ID: <CAM9d7cgaSPbnjoA6bv8fwkpoyc6nCdXOOrbmBm_jGbZbm3a_4w@mail.gmail.com>
Date:   Thu, 25 May 2023 12:14:53 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Ross Zwisler <zwisler@...omium.org>,
        Leo Yan <leo.yan@...aro.org>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Yang Jihong <yangjihong1@...wei.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 01/16] perf header: Make nodes dynamic in write_mem_topology

On Thu, May 25, 2023 at 12:12 AM Ian Rogers <irogers@...gle.com> wrote:
>
> Avoid a large static array, dynamically allocate the nodes avoiding a
> hard coded limited as well.
>
> Signed-off-by: Ian Rogers <irogers@...gle.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


>         }
>
>         *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
>