On Fri, Jun 13, 2025 at 12:21 AM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> This commit adds a new field mem_peak / "Peak memory (MiB)" field to a
> set of gathered statistics. The field is intended as an estimate for
> peak verifier memory consumption for processing of a given program.
>
> Mechanically stat is collected as follows:
> - At the beginning of handle_verif_mode() a new cgroup is created
> and veristat process is moved into this cgroup.
> - At each program load:
> - bpf_object__load() is split into bpf_object__prepare() and
> bpf_object__load() to avoid accounting for memory allocated for
> maps;
> - before bpf_object__load():
> - a write to "memory.peak" file of the new cgroup is used to reset
> cgroup statistics;
> - updated value is read from "memory.peak" file and stashed;
> - after bpf_object__load() "memory.peak" is read again and
> difference between new and stashed values is used as a metric.
>
> If any of the above steps fails veristat proceeds w/o collecting
> mem_peak information for a program, reporting mem_peak as -1.
>
> While memcg provides data in bytes (converted from pages), veristat
> converts it to megabytes to avoid jitter when comparing results of
> different executions.
>
> The change has no measurable impact on veristat running time.
>
> A correlation between "Peak states" and "Peak memory" fields provides
> a sanity check for gathered statistics, e.g. a sample of data for
> sched_ext programs:
>
> Program Peak states Peak memory (MiB)
> ------------------------ ----------- -----------------
> lavd_select_cpu 2153 44
> lavd_enqueue 1982 41
> lavd_dispatch 3480 28
> layered_dispatch 1417 17
> layered_enqueue 760 11
> lavd_cpu_offline 349 6
> lavd_cpu_online 349 6
> lavd_init 394 6
> rusty_init 350 5
> layered_select_cpu 391 4
> ...
> rusty_stopping 134 1
> arena_topology_node_init 170 0
>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> tools/testing/selftests/bpf/Makefile | 8 +
> tools/testing/selftests/bpf/veristat.c | 248 ++++++++++++++++++++++++-
> 2 files changed, 249 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index cf5ed3bee573..dd598ca771c5 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -841,6 +841,14 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \
> $(call msg,BINARY,,$@)
> $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
>
> +# This works around GCC warning about snprintf truncating strings like:
> +#
> +# char a[PATH_MAX], b[PATH_MAX];
> +# snprintf(a, "%s/foo", b); // triggers -Wformat-truncation
> +ifeq ($(LLVM),)
> +$(OUTPUT)/veristat.o: CFLAGS+=-Wno-format-truncation
fixed formatting around +=, and dropped LLVM check, I think that
should be handled by -Wno-unused-command-line-argument we set earlier
(`make LLVM=1 veristat` succeeded without any warnings for me, FWIW)
applied to bpf-next, thanks
> +endif
> +
> $(OUTPUT)/veristat.o: $(BPFOBJ)
> $(OUTPUT)/veristat: $(OUTPUT)/veristat.o
> $(call msg,BINARY,,$@)
[...]
> +/*
> + * Creates a cgroup at /sys/fs/cgroup/veristat-accounting-<pid>,
> + * moves current process to this cgroup.
> + */
> +static void create_stat_cgroup(void)
> +{
> + char cgroup_fs_mount[PATH_MAX];
> + char buf[PATH_MAX];
I hard-coded these to 4096 given we hard-coded 4095 below.
[...]
