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Fri, 22 May 2026 14:26:43 -0700 (PDT) Received: from ryzen ([2601:644:8000:5b5d:7285:c2ff:fe45:8a32]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beb58b386esm30195395ad.44.2026.05.22.14.26.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 May 2026 14:26:42 -0700 (PDT) From: Rosen Penev To: linux-trace-kernel@vger.kernel.org Cc: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org (open list:TRACING) Subject: [PATCHv2] trace: allocate fields with elt struct Date: Fri, 22 May 2026 14:26:27 -0700 Message-ID: <20260522212627.12406-1-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Use a flexible array member to embed the fields array in the tracing_map_elt allocation, reducing the number of allocations per element. Since the fields are now embedded in the struct, taking the address of a field through a const-qualified elt pointer yields a const-qualified pointer. Rather than adding casts, switch the comparison functions to take const void * parameters. These are all read-only operations. Assisted-by: OpenCode:BigPickle Signed-off-by: Rosen Penev --- v2: Rebased. kernel/trace/tracing_map.c | 41 ++++++++++++++++---------------------- kernel/trace/tracing_map.h | 8 ++++---- 2 files changed, 21 insertions(+), 28 deletions(-) diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c index d7922f40dbe2..928948b50737 100644 --- a/kernel/trace/tracing_map.c +++ b/kernel/trace/tracing_map.c @@ -125,32 +125,32 @@ u64 tracing_map_read_var_once(struct tracing_map_elt = *elt, unsigned int i) return (u64)atomic64_read(&elt->vars[i]); } =20 -int tracing_map_cmp_string(void *val_a, void *val_b) +int tracing_map_cmp_string(const void *val_a, const void *val_b) { - char *a =3D val_a; - char *b =3D val_b; + const char *a =3D val_a; + const char *b =3D val_b; =20 return strcmp(a, b); } =20 -int tracing_map_cmp_none(void *val_a, void *val_b) +int tracing_map_cmp_none(const void *val_a, const void *val_b) { return 0; } =20 -static int tracing_map_cmp_atomic64(void *val_a, void *val_b) +static int tracing_map_cmp_atomic64(const void *val_a, const void *val_b) { - u64 a =3D atomic64_read((atomic64_t *)val_a); - u64 b =3D atomic64_read((atomic64_t *)val_b); + u64 a =3D atomic64_read((const atomic64_t *)val_a); + u64 b =3D atomic64_read((const atomic64_t *)val_b); =20 return (a > b) ? 1 : ((a < b) ? -1 : 0); } =20 #define DEFINE_TRACING_MAP_CMP_FN(type) \ -static int tracing_map_cmp_##type(void *val_a, void *val_b) \ +static int tracing_map_cmp_##type(const void *val_a, const void *val_b) \ { \ - type a =3D (type)(*(u64 *)val_a); \ - type b =3D (type)(*(u64 *)val_b); \ + type a =3D (type)(*(const u64 *)val_a); \ + type b =3D (type)(*(const u64 *)val_b); \ \ return (a > b) ? 1 : ((a < b) ? -1 : 0); \ } @@ -383,7 +383,6 @@ static void __tracing_map_elt_free(struct tracing_map_e= lt *elt) if (!elt) return; =20 - kfree(elt->fields); kfree(elt->vars); kfree(elt->var_set); kfree(elt->key); @@ -406,7 +405,7 @@ static struct tracing_map_elt *tracing_map_elt_alloc(st= ruct tracing_map *map) struct tracing_map_elt *elt; int err =3D 0; =20 - elt =3D kzalloc_obj(*elt); + elt =3D kzalloc_flex(*elt, fields, map->n_fields); if (!elt) return ERR_PTR(-ENOMEM); =20 @@ -418,12 +417,6 @@ static struct tracing_map_elt *tracing_map_elt_alloc(s= truct tracing_map *map) goto free; } =20 - elt->fields =3D kzalloc_objs(*elt->fields, map->n_fields); - if (!elt->fields) { - err =3D -ENOMEM; - goto free; - } - elt->vars =3D kzalloc_objs(*elt->vars, map->n_vars); if (!elt->vars) { err =3D -ENOMEM; @@ -857,10 +850,10 @@ static int cmp_entries_sum(const void *A, const void = *B) { const struct tracing_map_elt *elt_a, *elt_b; const struct tracing_map_sort_entry *a, *b; - struct tracing_map_sort_key *sort_key; - struct tracing_map_field *field; + const struct tracing_map_sort_key *sort_key; + const struct tracing_map_field *field; tracing_map_cmp_fn_t cmp_fn; - void *val_a, *val_b; + const void *val_a, *val_b; int ret =3D 0; =20 a =3D *(const struct tracing_map_sort_entry **)A; @@ -888,10 +881,10 @@ static int cmp_entries_key(const void *A, const void = *B) { const struct tracing_map_elt *elt_a, *elt_b; const struct tracing_map_sort_entry *a, *b; - struct tracing_map_sort_key *sort_key; - struct tracing_map_field *field; + const struct tracing_map_sort_key *sort_key; + const struct tracing_map_field *field; tracing_map_cmp_fn_t cmp_fn; - void *val_a, *val_b; + const void *val_a, *val_b; int ret =3D 0; =20 a =3D *(const struct tracing_map_sort_entry **)A; diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h index 18a02959d77b..90a7fde5dd02 100644 --- a/kernel/trace/tracing_map.h +++ b/kernel/trace/tracing_map.h @@ -13,7 +13,7 @@ #define TRACING_MAP_VARS_MAX 16 #define TRACING_MAP_SORT_KEYS_MAX 2 =20 -typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b); +typedef int (*tracing_map_cmp_fn_t) (const void *val_a, const void *val_b); =20 /* * This is an overview of the tracing_map data structures and how they @@ -137,11 +137,11 @@ struct tracing_map_field { =20 struct tracing_map_elt { struct tracing_map *map; - struct tracing_map_field *fields; atomic64_t *vars; bool *var_set; void *key; void *private_data; + struct tracing_map_field fields[]; }; =20 struct tracing_map_entry { @@ -260,8 +260,8 @@ tracing_map_lookup(struct tracing_map *map, void *key); =20 extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, int field_is_signed); -extern int tracing_map_cmp_string(void *val_a, void *val_b); -extern int tracing_map_cmp_none(void *val_a, void *val_b); +extern int tracing_map_cmp_string(const void *val_a, const void *val_b); +extern int tracing_map_cmp_none(const void *val_a, const void *val_b); =20 extern void tracing_map_update_sum(struct tracing_map_elt *elt, unsigned int i, u64 n); --=20 2.54.0