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

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Date:   Thu, 25 May 2023 23:00:54 -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 7:39 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Thu, May 25, 2023 at 12:15 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > 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
>
> Not sure I follow. The reallocarray tests for failure, frees nodes and
> returns -ENOMEM on error.

Right, but I think it would leak the nodes when the
memory_node__read() fails.

Thanks,
Namhyung