[PATCH bpf-next v3 0/2] veristat: memory accounting for bpf programs

[PATCH bpf-next v3 0/2] veristat: memory accounting for bpf programs

[Eduard Zingerman]

When working on the verifier, it is sometimes interesting to know how a
particular change affects memory consumption. This patch-set modifies
veristat to provide such information. As a collateral, kernel needs an
update to make allocations reachable from BPF program load accountable
in memcg statistics.

Here is a sample output:

  Program          Peak states  Peak memory (MiB)
  ---------------  -----------  -----------------
  lavd_select_cpu         2153                 43
  lavd_enqueue            1982                 41
  lavd_dispatch           3480                 28

Technically, this is implemented by creating and entering a new cgroup
at the start of veristat execution. The difference between values from
cgroup "memory.peak" file before and after bpf_object__load() is used
as a metric.

To minimize measurements jitter data is collected in megabytes.

Changelog:
v2: https://lore.kernel.org/bpf/20250612130835.2478649-1-eddyz87@gmail.com/
v2 -> v3:
- bpf_verifier_state->jmp_history and
  bpf_verifier_env->explored_states allocations are switched from
  GFP_USER to GFP_KERNEL_ACCOUNT (Andrii, Alexei);
- veristat.c:STR macro removed, PATH_MAX-1 == 4095 is hard-coded in
  scanf format strings (Andrii);
- env->{orig,stat}_cgroup size changed to PATH_MAX (Andrii);
- snprintf_trunc() is removed, flag -Wno-format-truncation
  is added to CFLAGS for veristat.o when compiled with gcc;

v1: https://lore.kernel.org/bpf/20250605230609.1444980-1-eddyz87@gmail.com/
v1 -> v2:
- a single cgroup, created at the beginning of execution, is now used
  for measurements (Andrii, Mykyta);
- cgroup namespace is not created, as it turned out to be useless
  (Andrii);
- veristat no longer mounts cgroup fs or changes subtree_control,
  instead it looks for an existing mount point and reports an error if
  memory.peak file can't be opened (Andrii, Alexei);
- if 'mem_peak' statistics is not enabled, veristat skips cgroup
  setup;
- code sharing with cgroup_helpers.c was considered but was decided
  against to simplify veristat github sync.

Eduard Zingerman (2):
  bpf: include verifier memory allocations in memcg statistics
  veristat: memory accounting for bpf programs

 kernel/bpf/btf.c                       |  15 +-
 kernel/bpf/verifier.c                  |  69 +++----
 tools/testing/selftests/bpf/Makefile   |   8 +
 tools/testing/selftests/bpf/veristat.c | 248 ++++++++++++++++++++++++-
 4 files changed, 292 insertions(+), 48 deletions(-)

-- 
2.47.1

[PATCH bpf-next v3 1/2] bpf: include verifier memory allocations in memcg statistics

[Eduard Zingerman]

This commit adds __GFP_ACCOUNT flag to verifier induced memory
allocations. The intent is to account for all allocations reachable
from BPF_PROG_LOAD command, which is needed to track verifier memory
consumption in veristat. This includes allocations done in verifier.c,
and some allocations in btf.c, functions in log.c do not allocate.

There is also a utility function bpf_memcg_flags() which selectively
adds GFP_ACCOUNT flag depending on the `cgroup.memory=nobpf` option.
As far as I understand [1], the idea is to remove bpf_prog instances
and maps from memcg accounting as these objects do not strictly belong
to cgroup, hence it should not apply here.

(btf_parse_fields() is reachable from both program load and map
 creation, but allocated record is not persistent as is freed as soon
 as map_check_btf() exits).

[1] https://lore.kernel.org/all/20230210154734.4416-1-laoar.shao@gmail.com/

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/btf.c      | 15 +++++-----
 kernel/bpf/verifier.c | 69 ++++++++++++++++++++++---------------------
 2 files changed, 43 insertions(+), 41 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 1d2cf898e21e..682acb1ed234 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3443,7 +3443,8 @@ btf_find_graph_root(const struct btf *btf, const struct btf_type *pt,
 	node_field_name = strstr(value_type, ":");
 	if (!node_field_name)
 		return -EINVAL;
-	value_type = kstrndup(value_type, node_field_name - value_type, GFP_KERNEL | __GFP_NOWARN);
+	value_type = kstrndup(value_type, node_field_name - value_type,
+			      GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
 	if (!value_type)
 		return -ENOMEM;
 	id = btf_find_by_name_kind(btf, value_type, BTF_KIND_STRUCT);
@@ -3958,7 +3959,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	/* This needs to be kzalloc to zero out padding and unused fields, see
 	 * comment in btf_record_equal.
 	 */
-	rec = kzalloc(struct_size(rec, fields, cnt), GFP_KERNEL | __GFP_NOWARN);
+	rec = kzalloc(struct_size(rec, fields, cnt), GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
 	if (!rec)
 		return ERR_PTR(-ENOMEM);
 
@@ -9019,7 +9020,7 @@ static struct bpf_cand_cache *populate_cand_cache(struct bpf_cand_cache *cands,
 		bpf_free_cands_from_cache(*cc);
 		*cc = NULL;
 	}
-	new_cands = kmemdup(cands, sizeof_cands(cands->cnt), GFP_KERNEL);
+	new_cands = kmemdup(cands, sizeof_cands(cands->cnt), GFP_KERNEL_ACCOUNT);
 	if (!new_cands) {
 		bpf_free_cands(cands);
 		return ERR_PTR(-ENOMEM);
@@ -9027,7 +9028,7 @@ static struct bpf_cand_cache *populate_cand_cache(struct bpf_cand_cache *cands,
 	/* strdup the name, since it will stay in cache.
 	 * the cands->name points to strings in prog's BTF and the prog can be unloaded.
 	 */
-	new_cands->name = kmemdup_nul(cands->name, cands->name_len, GFP_KERNEL);
+	new_cands->name = kmemdup_nul(cands->name, cands->name_len, GFP_KERNEL_ACCOUNT);
 	bpf_free_cands(cands);
 	if (!new_cands->name) {
 		kfree(new_cands);
@@ -9111,7 +9112,7 @@ bpf_core_add_cands(struct bpf_cand_cache *cands, const struct btf *targ_btf,
 			continue;
 
 		/* most of the time there is only one candidate for a given kind+name pair */
-		new_cands = kmalloc(sizeof_cands(cands->cnt + 1), GFP_KERNEL);
+		new_cands = kmalloc(sizeof_cands(cands->cnt + 1), GFP_KERNEL_ACCOUNT);
 		if (!new_cands) {
 			bpf_free_cands(cands);
 			return ERR_PTR(-ENOMEM);
@@ -9228,7 +9229,7 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
 	/* ~4k of temp memory necessary to convert LLVM spec like "0:1:0:5"
 	 * into arrays of btf_ids of struct fields and array indices.
 	 */
-	specs = kcalloc(3, sizeof(*specs), GFP_KERNEL);
+	specs = kcalloc(3, sizeof(*specs), GFP_KERNEL_ACCOUNT);
 	if (!specs)
 		return -ENOMEM;
 
@@ -9253,7 +9254,7 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
 			goto out;
 		}
 		if (cc->cnt) {
-			cands.cands = kcalloc(cc->cnt, sizeof(*cands.cands), GFP_KERNEL);
+			cands.cands = kcalloc(cc->cnt, sizeof(*cands.cands), GFP_KERNEL_ACCOUNT);
 			if (!cands.cands) {
 				err = -ENOMEM;
 				goto out;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c378074516cf..fd81cff11617 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1404,7 +1404,7 @@ static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
 		goto out;
 
 	alloc_size = kmalloc_size_roundup(size_mul(new_n, size));
-	new_arr = krealloc(arr, alloc_size, GFP_KERNEL);
+	new_arr = krealloc(arr, alloc_size, GFP_KERNEL_ACCOUNT);
 	if (!new_arr) {
 		kfree(arr);
 		return NULL;
@@ -1421,7 +1421,7 @@ static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
 static int copy_reference_state(struct bpf_verifier_state *dst, const struct bpf_verifier_state *src)
 {
 	dst->refs = copy_array(dst->refs, src->refs, src->acquired_refs,
-			       sizeof(struct bpf_reference_state), GFP_KERNEL);
+			       sizeof(struct bpf_reference_state), GFP_KERNEL_ACCOUNT);
 	if (!dst->refs)
 		return -ENOMEM;
 
@@ -1440,7 +1440,7 @@ static int copy_stack_state(struct bpf_func_state *dst, const struct bpf_func_st
 	size_t n = src->allocated_stack / BPF_REG_SIZE;
 
 	dst->stack = copy_array(dst->stack, src->stack, n, sizeof(struct bpf_stack_state),
-				GFP_KERNEL);
+				GFP_KERNEL_ACCOUNT);
 	if (!dst->stack)
 		return -ENOMEM;
 
@@ -1731,7 +1731,7 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 
 	dst_state->jmp_history = copy_array(dst_state->jmp_history, src->jmp_history,
 					  src->jmp_history_cnt, sizeof(*dst_state->jmp_history),
-					  GFP_USER);
+					  GFP_KERNEL_ACCOUNT);
 	if (!dst_state->jmp_history)
 		return -ENOMEM;
 	dst_state->jmp_history_cnt = src->jmp_history_cnt;
@@ -1760,7 +1760,7 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 	for (i = 0; i <= src->curframe; i++) {
 		dst = dst_state->frame[i];
 		if (!dst) {
-			dst = kzalloc(sizeof(*dst), GFP_KERNEL);
+			dst = kzalloc(sizeof(*dst), GFP_KERNEL_ACCOUNT);
 			if (!dst)
 				return -ENOMEM;
 			dst_state->frame[i] = dst;
@@ -1874,7 +1874,7 @@ static struct bpf_scc_visit *scc_visit_alloc(struct bpf_verifier_env *env,
 	info = env->scc_info[scc];
 	num_visits = info ? info->num_visits : 0;
 	new_sz = sizeof(*info) + sizeof(struct bpf_scc_visit) * (num_visits + 1);
-	info = kvrealloc(env->scc_info[scc], new_sz, GFP_KERNEL);
+	info = kvrealloc(env->scc_info[scc], new_sz, GFP_KERNEL_ACCOUNT);
 	if (!info)
 		return NULL;
 	env->scc_info[scc] = info;
@@ -2095,7 +2095,7 @@ static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
 	struct bpf_verifier_stack_elem *elem;
 	int err;
 
-	elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
+	elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL_ACCOUNT);
 	if (!elem)
 		goto err;
 
@@ -2862,7 +2862,7 @@ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env,
 	struct bpf_verifier_stack_elem *elem;
 	struct bpf_func_state *frame;
 
-	elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
+	elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL_ACCOUNT);
 	if (!elem)
 		goto err;
 
@@ -2885,7 +2885,7 @@ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env,
 	 */
 	elem->st.branches = 1;
 	elem->st.in_sleepable = is_sleepable;
-	frame = kzalloc(sizeof(*frame), GFP_KERNEL);
+	frame = kzalloc(sizeof(*frame), GFP_KERNEL_ACCOUNT);
 	if (!frame)
 		goto err;
 	init_func_state(env, frame,
@@ -3237,7 +3237,7 @@ static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, s16 offset)
 			return -EINVAL;
 		}
 
-		tab = kzalloc(sizeof(*tab), GFP_KERNEL);
+		tab = kzalloc(sizeof(*tab), GFP_KERNEL_ACCOUNT);
 		if (!tab)
 			return -ENOMEM;
 		prog_aux->kfunc_tab = tab;
@@ -3253,7 +3253,7 @@ static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, s16 offset)
 		return 0;
 
 	if (!btf_tab && offset) {
-		btf_tab = kzalloc(sizeof(*btf_tab), GFP_KERNEL);
+		btf_tab = kzalloc(sizeof(*btf_tab), GFP_KERNEL_ACCOUNT);
 		if (!btf_tab)
 			return -ENOMEM;
 		prog_aux->kfunc_btf_tab = btf_tab;
@@ -3939,7 +3939,7 @@ static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_st
 
 	cnt++;
 	alloc_size = kmalloc_size_roundup(size_mul(cnt, sizeof(*p)));
-	p = krealloc(cur->jmp_history, alloc_size, GFP_USER);
+	p = krealloc(cur->jmp_history, alloc_size, GFP_KERNEL_ACCOUNT);
 	if (!p)
 		return -ENOMEM;
 	cur->jmp_history = p;
@@ -10356,7 +10356,7 @@ static int setup_func_entry(struct bpf_verifier_env *env, int subprog, int calls
 	}
 
 	caller = state->frame[state->curframe];
-	callee = kzalloc(sizeof(*callee), GFP_KERNEL);
+	callee = kzalloc(sizeof(*callee), GFP_KERNEL_ACCOUNT);
 	if (!callee)
 		return -ENOMEM;
 	state->frame[state->curframe + 1] = callee;
@@ -17693,17 +17693,18 @@ static int check_cfg(struct bpf_verifier_env *env)
 	int *insn_stack, *insn_state, *insn_postorder;
 	int ex_insn_beg, i, ret = 0;
 
-	insn_state = env->cfg.insn_state = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
+	insn_state = env->cfg.insn_state = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
 	if (!insn_state)
 		return -ENOMEM;
 
-	insn_stack = env->cfg.insn_stack = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
+	insn_stack = env->cfg.insn_stack = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
 	if (!insn_stack) {
 		kvfree(insn_state);
 		return -ENOMEM;
 	}
 
-	insn_postorder = env->cfg.insn_postorder = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
+	insn_postorder = env->cfg.insn_postorder =
+		kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
 	if (!insn_postorder) {
 		kvfree(insn_state);
 		kvfree(insn_stack);
@@ -17837,7 +17838,7 @@ static int check_btf_func_early(struct bpf_verifier_env *env,
 	urecord = make_bpfptr(attr->func_info, uattr.is_kernel);
 	min_size = min_t(u32, krec_size, urec_size);
 
-	krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL | __GFP_NOWARN);
+	krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
 	if (!krecord)
 		return -ENOMEM;
 
@@ -17937,7 +17938,7 @@ static int check_btf_func(struct bpf_verifier_env *env,
 	urecord = make_bpfptr(attr->func_info, uattr.is_kernel);
 
 	krecord = prog->aux->func_info;
-	info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL | __GFP_NOWARN);
+	info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
 	if (!info_aux)
 		return -ENOMEM;
 
@@ -18023,7 +18024,7 @@ static int check_btf_line(struct bpf_verifier_env *env,
 	 * pass in a smaller bpf_line_info object.
 	 */
 	linfo = kvcalloc(nr_linfo, sizeof(struct bpf_line_info),
-			 GFP_KERNEL | __GFP_NOWARN);
+			 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
 	if (!linfo)
 		return -ENOMEM;
 
@@ -19408,7 +19409,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 			if (loop) {
 				struct bpf_scc_backedge *backedge;
 
-				backedge = kzalloc(sizeof(*backedge), GFP_KERNEL);
+				backedge = kzalloc(sizeof(*backedge), GFP_KERNEL_ACCOUNT);
 				if (!backedge)
 					return -ENOMEM;
 				err = copy_verifier_state(&backedge->state, cur);
@@ -19472,7 +19473,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 	 * When looping the sl->state.branches will be > 0 and this state
 	 * will not be considered for equivalence until branches == 0.
 	 */
-	new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL);
+	new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL_ACCOUNT);
 	if (!new_sl)
 		return -ENOMEM;
 	env->total_states++;
@@ -22976,13 +22977,13 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 	env->prev_linfo = NULL;
 	env->pass_cnt++;
 
-	state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL);
+	state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL_ACCOUNT);
 	if (!state)
 		return -ENOMEM;
 	state->curframe = 0;
 	state->speculative = false;
 	state->branches = 1;
-	state->frame[0] = kzalloc(sizeof(struct bpf_func_state), GFP_KERNEL);
+	state->frame[0] = kzalloc(sizeof(struct bpf_func_state), GFP_KERNEL_ACCOUNT);
 	if (!state->frame[0]) {
 		kfree(state);
 		return -ENOMEM;
@@ -23208,7 +23209,7 @@ static void print_verification_stats(struct bpf_verifier_env *env)
 int bpf_prog_ctx_arg_info_init(struct bpf_prog *prog,
 			       const struct bpf_ctx_arg_aux *info, u32 cnt)
 {
-	prog->aux->ctx_arg_info = kmemdup_array(info, cnt, sizeof(*info), GFP_KERNEL);
+	prog->aux->ctx_arg_info = kmemdup_array(info, cnt, sizeof(*info), GFP_KERNEL_ACCOUNT);
 	prog->aux->ctx_arg_info_size = cnt;
 
 	return prog->aux->ctx_arg_info ? 0 : -ENOMEM;
@@ -24152,7 +24153,7 @@ static int compute_live_registers(struct bpf_verifier_env *env)
 	 * - repeat the computation while {in,out} fields changes for
 	 *   any instruction.
 	 */
-	state = kvcalloc(insn_cnt, sizeof(*state), GFP_KERNEL);
+	state = kvcalloc(insn_cnt, sizeof(*state), GFP_KERNEL_ACCOUNT);
 	if (!state) {
 		err = -ENOMEM;
 		goto out;
@@ -24244,10 +24245,10 @@ static int compute_scc(struct bpf_verifier_env *env)
 	 * - 'low[t] == n' => smallest preorder number of the vertex reachable from 't' is 'n';
 	 * - 'dfs' DFS traversal stack, used to emulate explicit recursion.
 	 */
-	stack = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
-	pre = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
-	low = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
-	dfs = kvcalloc(insn_cnt, sizeof(*dfs), GFP_KERNEL);
+	stack = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
+	pre = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
+	low = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL_ACCOUNT);
+	dfs = kvcalloc(insn_cnt, sizeof(*dfs), GFP_KERNEL_ACCOUNT);
 	if (!stack || !pre || !low || !dfs) {
 		err = -ENOMEM;
 		goto exit;
@@ -24381,7 +24382,7 @@ static int compute_scc(struct bpf_verifier_env *env)
 			dfs_sz--;
 		}
 	}
-	env->scc_info = kvcalloc(next_scc_id, sizeof(*env->scc_info), GFP_KERNEL);
+	env->scc_info = kvcalloc(next_scc_id, sizeof(*env->scc_info), GFP_KERNEL_ACCOUNT);
 	if (!env->scc_info) {
 		err = -ENOMEM;
 		goto exit;
@@ -24409,7 +24410,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	/* 'struct bpf_verifier_env' can be global, but since it's not small,
 	 * allocate/free it every time bpf_check() is called
 	 */
-	env = kvzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
+	env = kvzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL_ACCOUNT);
 	if (!env)
 		return -ENOMEM;
 
@@ -24472,7 +24473,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 
 	env->explored_states = kvcalloc(state_htab_size(env),
 				       sizeof(struct list_head),
-				       GFP_USER);
+				       GFP_KERNEL_ACCOUNT);
 	ret = -ENOMEM;
 	if (!env->explored_states)
 		goto skip_full_check;
@@ -24603,7 +24604,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 		/* if program passed verifier, update used_maps in bpf_prog_info */
 		env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
 							  sizeof(env->used_maps[0]),
-							  GFP_KERNEL);
+							  GFP_KERNEL_ACCOUNT);
 
 		if (!env->prog->aux->used_maps) {
 			ret = -ENOMEM;
@@ -24618,7 +24619,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 		/* if program passed verifier, update used_btfs in bpf_prog_aux */
 		env->prog->aux->used_btfs = kmalloc_array(env->used_btf_cnt,
 							  sizeof(env->used_btfs[0]),
-							  GFP_KERNEL);
+							  GFP_KERNEL_ACCOUNT);
 		if (!env->prog->aux->used_btfs) {
 			ret = -ENOMEM;
 			goto err_release_maps;
-- 
2.47.1

[PATCH bpf-next v3 2/2] veristat: memory accounting for bpf programs

[Eduard Zingerman]

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@gmail.com>
---
 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
+endif
+
 $(OUTPUT)/veristat.o: $(BPFOBJ)
 $(OUTPUT)/veristat: $(OUTPUT)/veristat.o
 	$(call msg,BINARY,,$@)
diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index b2bb20b00952..0a3be1282402 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -49,6 +49,7 @@ enum stat_id {
 	STACK,
 	PROG_TYPE,
 	ATTACH_TYPE,
+	MEMORY_PEAK,
 
 	FILE_NAME,
 	PROG_NAME,
@@ -208,6 +209,9 @@ static struct env {
 	int top_src_lines;
 	struct var_preset *presets;
 	int npresets;
+	char orig_cgroup[PATH_MAX];
+	char stat_cgroup[PATH_MAX];
+	int memory_peak_fd;
 } env;
 
 static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
@@ -219,6 +223,22 @@ static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va
 	return vfprintf(stderr, format, args);
 }
 
+#define log_errno(fmt, ...) log_errno_aux(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
+
+__printf(3, 4)
+static int log_errno_aux(const char *file, int line, const char *fmt, ...)
+{
+	int err = -errno;
+	va_list ap;
+
+	va_start(ap, fmt);
+	fprintf(stderr, "%s:%d: ", file, line);
+	vfprintf(stderr, fmt, ap);
+	fprintf(stderr, " failed with error '%s'.\n", strerror(errno));
+	va_end(ap);
+	return err;
+}
+
 #ifndef VERISTAT_VERSION
 #define VERISTAT_VERSION "<kernel>"
 #endif
@@ -734,13 +754,13 @@ static int append_file_from_file(const char *path)
 }
 
 static const struct stat_specs default_csv_output_spec = {
-	.spec_cnt = 14,
+	.spec_cnt = 15,
 	.ids = {
 		FILE_NAME, PROG_NAME, VERDICT, DURATION,
 		TOTAL_INSNS, TOTAL_STATES, PEAK_STATES,
 		MAX_STATES_PER_INSN, MARK_READ_MAX_LEN,
 		SIZE, JITED_SIZE, PROG_TYPE, ATTACH_TYPE,
-		STACK,
+		STACK, MEMORY_PEAK,
 	},
 };
 
@@ -781,6 +801,7 @@ static struct stat_def {
 	[STACK] = {"Stack depth", {"stack_depth", "stack"}, },
 	[PROG_TYPE] = { "Program type", {"prog_type"}, },
 	[ATTACH_TYPE] = { "Attach type", {"attach_type", }, },
+	[MEMORY_PEAK] = { "Peak memory (MiB)", {"mem_peak", }, },
 };
 
 static bool parse_stat_id_var(const char *name, size_t len, int *id,
@@ -1278,16 +1299,214 @@ static int max_verifier_log_size(void)
 	return log_size;
 }
 
+static bool output_stat_enabled(int id)
+{
+	int i;
+
+	for (i = 0; i < env.output_spec.spec_cnt; i++)
+		if (env.output_spec.ids[i] == id)
+			return true;
+	return false;
+}
+
+__printf(2, 3)
+static int write_one_line(const char *file, const char *fmt, ...)
+{
+	int err, saved_errno;
+	va_list ap;
+	FILE *f;
+
+	f = fopen(file, "w");
+	if (!f)
+		return -1;
+
+	va_start(ap, fmt);
+	errno = 0;
+	err = vfprintf(f, fmt, ap);
+	saved_errno = errno;
+	va_end(ap);
+	fclose(f);
+	errno = saved_errno;
+	return err < 0 ? -1 : 0;
+}
+
+__scanf(3, 4)
+static int scanf_one_line(const char *file, int fields_expected, const char *fmt, ...)
+{
+	int res = 0, saved_errno = 0;
+	char *line = NULL;
+	size_t line_len;
+	va_list ap;
+	FILE *f;
+
+	f = fopen(file, "r");
+	if (!f)
+		return -1;
+
+	va_start(ap, fmt);
+	while (getline(&line, &line_len, f) > 0) {
+		res = vsscanf(line, fmt, ap);
+		if (res == fields_expected)
+			goto out;
+	}
+	if (ferror(f)) {
+		saved_errno = errno;
+		res = -1;
+	}
+
+out:
+	va_end(ap);
+	free(line);
+	fclose(f);
+	errno = saved_errno;
+	return res;
+}
+
+static void destroy_stat_cgroup(void)
+{
+	char buf[PATH_MAX];
+	int err;
+
+	close(env.memory_peak_fd);
+
+	if (env.orig_cgroup[0]) {
+		snprintf(buf, sizeof(buf), "%s/cgroup.procs", env.orig_cgroup);
+		err = write_one_line(buf, "%d\n", getpid());
+		if (err < 0)
+			log_errno("moving self to original cgroup %s\n", env.orig_cgroup);
+	}
+
+	if (env.stat_cgroup[0]) {
+		err = rmdir(env.stat_cgroup);
+		if (err < 0)
+			log_errno("deletion of cgroup %s", env.stat_cgroup);
+	}
+
+	env.memory_peak_fd = -1;
+	env.orig_cgroup[0] = 0;
+	env.stat_cgroup[0] = 0;
+}
+
+/*
+ * 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];
+	int err;
+
+	env.memory_peak_fd = -1;
+
+	if (!output_stat_enabled(MEMORY_PEAK))
+		return;
+
+	err = scanf_one_line("/proc/self/mounts", 2, "%*s %4095s cgroup2 %s",
+			     cgroup_fs_mount, buf);
+	if (err != 2) {
+		if (err < 0)
+			log_errno("reading /proc/self/mounts");
+		else if (!env.quiet)
+			fprintf(stderr, "Can't find cgroupfs v2 mount point.\n");
+		goto err_out;
+	}
+
+	/* cgroup-v2.rst promises the line "0::<group>" for cgroups v2 */
+	err = scanf_one_line("/proc/self/cgroup", 1, "0::%4095s", buf);
+	if (err != 1) {
+		if (err < 0)
+			log_errno("reading /proc/self/cgroup");
+		else if (!env.quiet)
+			fprintf(stderr, "Can't infer veristat process cgroup.");
+		goto err_out;
+	}
+
+	snprintf(env.orig_cgroup, sizeof(env.orig_cgroup), "%s/%s", cgroup_fs_mount, buf);
+
+	snprintf(buf, sizeof(buf), "%s/veristat-accounting-%d", cgroup_fs_mount, getpid());
+	err = mkdir(buf, 0777);
+	if (err < 0) {
+		log_errno("creation of cgroup %s", buf);
+		goto err_out;
+	}
+	strcpy(env.stat_cgroup, buf);
+
+	snprintf(buf, sizeof(buf), "%s/cgroup.procs", env.stat_cgroup);
+	err = write_one_line(buf, "%d\n", getpid());
+	if (err < 0) {
+		log_errno("entering cgroup %s", buf);
+		goto err_out;
+	}
+
+	snprintf(buf, sizeof(buf), "%s/memory.peak", env.stat_cgroup);
+	env.memory_peak_fd = open(buf, O_RDWR | O_APPEND);
+	if (env.memory_peak_fd < 0) {
+		log_errno("opening %s", buf);
+		goto err_out;
+	}
+
+	return;
+
+err_out:
+	if (!env.quiet)
+		fprintf(stderr, "Memory usage metric unavailable.\n");
+	destroy_stat_cgroup();
+}
+
+/* Current value of /sys/fs/cgroup/veristat-accounting-<pid>/memory.peak */
+static long cgroup_memory_peak(void)
+{
+	long err, memory_peak;
+	char buf[32];
+
+	if (env.memory_peak_fd < 0)
+		return -1;
+
+	err = pread(env.memory_peak_fd, buf, sizeof(buf) - 1, 0);
+	if (err <= 0) {
+		log_errno("pread(%s/memory.peak)", env.stat_cgroup);
+		return -1;
+	}
+
+	buf[err] = 0;
+	errno = 0;
+	memory_peak = strtoll(buf, NULL, 10);
+	if (errno) {
+		log_errno("%s/memory.peak:strtoll(%s)", env.stat_cgroup, buf);
+		return -1;
+	}
+
+	return memory_peak;
+}
+
+static int reset_stat_cgroup(void)
+{
+	char buf[] = "r\n";
+	int err;
+
+	if (env.memory_peak_fd < 0)
+		return -1;
+
+	err = pwrite(env.memory_peak_fd, buf, sizeof(buf), 0);
+	if (err <= 0) {
+		log_errno("pwrite(%s/memory.peak)", env.stat_cgroup);
+		return -1;
+	}
+	return 0;
+}
+
 static int process_prog(const char *filename, struct bpf_object *obj, struct bpf_program *prog)
 {
 	const char *base_filename = basename(strdupa(filename));
 	const char *prog_name = bpf_program__name(prog);
+	long mem_peak_a, mem_peak_b, mem_peak = -1;
 	char *buf;
 	int buf_sz, log_level;
 	struct verif_stats *stats;
 	struct bpf_prog_info info;
 	__u32 info_len = sizeof(info);
-	int err = 0;
+	int err = 0, cgroup_err;
 	void *tmp;
 	int fd;
 
@@ -1332,7 +1551,15 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf
 	if (env.force_reg_invariants)
 		bpf_program__set_flags(prog, bpf_program__flags(prog) | BPF_F_TEST_REG_INVARIANTS);
 
-	err = bpf_object__load(obj);
+	err = bpf_object__prepare(obj);
+	if (!err) {
+		cgroup_err = reset_stat_cgroup();
+		mem_peak_a = cgroup_memory_peak();
+		err = bpf_object__load(obj);
+		mem_peak_b = cgroup_memory_peak();
+		if (!cgroup_err && mem_peak_a >= 0 && mem_peak_b >= 0)
+			mem_peak = mem_peak_b - mem_peak_a;
+	}
 	env.progs_processed++;
 
 	stats->file_name = strdup(base_filename);
@@ -1341,6 +1568,7 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf
 	stats->stats[SIZE] = bpf_program__insn_cnt(prog);
 	stats->stats[PROG_TYPE] = bpf_program__type(prog);
 	stats->stats[ATTACH_TYPE] = bpf_program__expected_attach_type(prog);
+	stats->stats[MEMORY_PEAK] = mem_peak < 0 ? -1 : mem_peak / (1024 * 1024);
 
 	memset(&info, 0, info_len);
 	fd = bpf_program__fd(prog);
@@ -1824,6 +2052,7 @@ static int cmp_stat(const struct verif_stats *s1, const struct verif_stats *s2,
 	case TOTAL_STATES:
 	case PEAK_STATES:
 	case MAX_STATES_PER_INSN:
+	case MEMORY_PEAK:
 	case MARK_READ_MAX_LEN: {
 		long v1 = s1->stats[id];
 		long v2 = s2->stats[id];
@@ -2053,6 +2282,7 @@ static void prepare_value(const struct verif_stats *s, enum stat_id id,
 	case STACK:
 	case SIZE:
 	case JITED_SIZE:
+	case MEMORY_PEAK:
 		*val = s ? s->stats[id] : 0;
 		break;
 	default:
@@ -2139,6 +2369,7 @@ static int parse_stat_value(const char *str, enum stat_id id, struct verif_stats
 	case MARK_READ_MAX_LEN:
 	case SIZE:
 	case JITED_SIZE:
+	case MEMORY_PEAK:
 	case STACK: {
 		long val;
 		int err, n;
@@ -2776,7 +3007,7 @@ static void output_prog_stats(void)
 
 static int handle_verif_mode(void)
 {
-	int i, err;
+	int i, err = 0;
 
 	if (env.filename_cnt == 0) {
 		fprintf(stderr, "Please provide path to BPF object file!\n\n");
@@ -2784,11 +3015,12 @@ static int handle_verif_mode(void)
 		return -EINVAL;
 	}
 
+	create_stat_cgroup();
 	for (i = 0; i < env.filename_cnt; i++) {
 		err = process_obj(env.filenames[i]);
 		if (err) {
 			fprintf(stderr, "Failed to process '%s': %d\n", env.filenames[i], err);
-			return err;
+			goto out;
 		}
 	}
 
@@ -2796,7 +3028,9 @@ static int handle_verif_mode(void)
 
 	output_prog_stats();
 
-	return 0;
+out:
+	destroy_stat_cgroup();
+	return err;
 }
 
 static int handle_replay_mode(void)
-- 
2.47.1

Re: [PATCH bpf-next v3 2/2] veristat: memory accounting for bpf programs

[Andrii Nakryiko]

On Fri, Jun 13, 2025 at 12:21 AM Eduard Zingerman <eddyz87@gmail.com> 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@gmail.com>
> ---
>  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.

[...]

Re: [PATCH bpf-next v3 0/2] veristat: memory accounting for bpf programs

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Fri, 13 Jun 2025 00:21:45 -0700 you wrote:
> When working on the verifier, it is sometimes interesting to know how a
> particular change affects memory consumption. This patch-set modifies
> veristat to provide such information. As a collateral, kernel needs an
> update to make allocations reachable from BPF program load accountable
> in memcg statistics.
> 
> Here is a sample output:
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3,1/2] bpf: include verifier memory allocations in memcg statistics
    https://git.kernel.org/bpf/bpf-next/c/43736ec3e027
  - [bpf-next,v3,2/2] veristat: memory accounting for bpf programs
    (no matching commit)

You are awesome, thank you!
-- 
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