From 8b1042c425f6a5a9fb57c5e1d5ecf5247cf899a6 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 15 Aug 2024 15:38:23 -0700 Subject: [PATCH] perf annotate-data: Set bitfield member offset and size properly The bitfield members might not have DW_AT_data_member_location. Let's use DW_AT_data_bit_offset to set the member offset correct. Also use DW_AT_bit_size for the name like in a C program. Before: Annotate type: 'struct sk_buff' (1 samples) Percent Offset Size Field - 100.00 0 232 struct sk_buff { + 0.00 0 24 union ; + 0.00 24 8 union ; + 0.00 32 8 union ; 0.00 40 48 char[] cb; + 0.00 88 16 union ; 0.00 104 8 long unsigned int _nfct; 100.00 112 4 unsigned int len; 0.00 116 4 unsigned int data_len; 0.00 120 2 __u16 mac_len; 0.00 122 2 __u16 hdr_len; 0.00 124 2 __u16 queue_mapping; 0.00 126 0 __u8[] __cloned_offset; 0.00 0 1 __u8 cloned; 0.00 0 1 __u8 nohdr; 0.00 0 1 __u8 fclone; 0.00 0 1 __u8 peeked; 0.00 0 1 __u8 head_frag; 0.00 0 1 __u8 pfmemalloc; 0.00 0 1 __u8 pp_recycle; 0.00 127 1 __u8 active_extensions; + 0.00 128 60 union ; 0.00 188 4 sk_buff_data_t tail; 0.00 192 4 sk_buff_data_t end; 0.00 200 8 unsigned char* head; After: Annotate type: 'struct sk_buff' (1 samples) Percent Offset Size Field - 100.00 0 232 struct sk_buff { + 0.00 0 24 union ; + 0.00 24 8 union ; + 0.00 32 8 union ; 0.00 40 48 char[] cb + 0.00 88 16 union ; 0.00 104 8 long unsigned int _nfct; 100.00 112 4 unsigned int len; 0.00 116 4 unsigned int data_len; 0.00 120 2 __u16 mac_len; 0.00 122 2 __u16 hdr_len; 0.00 124 2 __u16 queue_mapping; 0.00 126 0 __u8[] __cloned_offset; 0.00 126 1 __u8 cloned:1; 0.00 126 1 __u8 nohdr:1; 0.00 126 1 __u8 fclone:2; 0.00 126 1 __u8 peeked:1; 0.00 126 1 __u8 head_frag:1; 0.00 126 1 __u8 pfmemalloc:1; 0.00 126 1 __u8 pp_recycle:1; 0.00 127 1 __u8 active_extensions; + 0.00 128 60 union ; 0.00 188 4 sk_buff_data_t tail; 0.00 192 4 sk_buff_data_t end; 0.00 200 8 unsigned char* head; Commiter notes: Collect some data: root@number:~# perf mem record -a --ldlat 5 -- ping -s 8193 -f 192.168.86.1 Memory events are enabled on a subset of CPUs: 16-27 PING 192.168.86.1 (192.168.86.1) 8193(8221) bytes of data. .^C --- 192.168.86.1 ping statistics --- 13881 packets transmitted, 13880 received, 0.00720409% packet loss, time 8664ms rtt min/avg/max/mdev = 0.510/0.599/7.768/0.115 ms, ipg/ewma 0.624/0.593 ms [ perf record: Woken up 8 times to write data ] [ perf record: Captured and wrote 14.877 MB perf.data (46785 samples) ] root@number:~# root@number:~# perf evlist cpu_atom/mem-loads,ldlat=5/P cpu_atom/mem-stores/P dummy:u root@number:~# perf evlist -v cpu_atom/mem-loads,ldlat=5/P: type: 10 (cpu_atom), size: 136, config: 0x5d0 (mem-loads), { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|ADDR|CPU|PERIOD|IDENTIFIER|DATA_SRC|WEIGHT_STRUCT, read_format: ID|LOST, disabled: 1, inherit: 1, freq: 1, precise_ip: 3, sample_id_all: 1, { bp_addr, config1 }: 0x7 cpu_atom/mem-stores/P: type: 10 (cpu_atom), size: 136, config: 0x6d0 (mem-stores), { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|ADDR|CPU|PERIOD|IDENTIFIER|DATA_SRC|WEIGHT_STRUCT, read_format: ID|LOST, disabled: 1, inherit: 1, freq: 1, precise_ip: 3, sample_id_all: 1 dummy:u: type: 1 (software), size: 136, config: 0x9 (PERF_COUNT_SW_DUMMY), { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|ADDR|CPU|IDENTIFIER|DATA_SRC|WEIGHT_STRUCT, read_format: ID|LOST, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, task: 1, mmap_data: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1 root@number:~# Ok, now lets see what changes from before this patch to after it: root@number:~# perf annotate --data-type > /tmp/before Apply the patch, build: root@number:~# perf annotate --data-type > /tmp/after The first hunk of the diff, for a glib data structure, in userspace, look at those bitfields: root@number:~# diff -u10 /tmp/before /tmp/after | head -20 --- /tmp/before 2024-08-20 17:29:58.306765780 -0300 +++ /tmp/after 2024-08-20 17:33:13.210582596 -0300 @@ -163,22 +163,22 @@ Annotate type: 'GHashTable' in /usr/lib64/libglib-2.0.so.0.8000.3 (1 samples): ============================================================================ Percent offset size field 100.00 0 96 GHashTable { 0.00 0 8 gsize size; 0.00 8 4 gint mod; 100.00 12 4 guint mask; 0.00 16 4 guint nnodes; 0.00 20 4 guint noccupied; - 0.00 0 4 guint have_big_keys; - 0.00 0 4 guint have_big_values; + 0.00 24 1 guint have_big_keys:1; + 0.00 24 1 guint have_big_values:1; 0.00 32 8 gpointer keys; 0.00 40 8 guint* hashes; 0.00 48 8 gpointer values; root@number:~# As advertised :-) Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Athira Rajeev Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20240815223823.2402285-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/annotate-data.c | 34 +++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c index aa330c7d8edd..e5589268cb42 100644 --- a/tools/perf/util/annotate-data.c +++ b/tools/perf/util/annotate-data.c @@ -202,7 +202,7 @@ static int __add_member_cb(Dwarf_Die *die, void *arg) struct annotated_member *parent = arg; struct annotated_member *member; Dwarf_Die member_type, die_mem; - Dwarf_Word size, loc; + Dwarf_Word size, loc, bit_size = 0; Dwarf_Attribute attr; struct strbuf sb; int tag; @@ -226,15 +226,37 @@ static int __add_member_cb(Dwarf_Die *die, void *arg) if (dwarf_aggregate_size(&die_mem, &size) < 0) size = 0; - if (!dwarf_attr_integrate(die, DW_AT_data_member_location, &attr)) - loc = 0; - else + if (dwarf_attr_integrate(die, DW_AT_data_member_location, &attr)) dwarf_formudata(&attr, &loc); + else { + /* bitfield member */ + if (dwarf_attr_integrate(die, DW_AT_data_bit_offset, &attr) && + dwarf_formudata(&attr, &loc) == 0) + loc /= 8; + else + loc = 0; + + if (dwarf_attr_integrate(die, DW_AT_bit_size, &attr) && + dwarf_formudata(&attr, &bit_size) == 0) + size = (bit_size + 7) / 8; + } member->type_name = strbuf_detach(&sb, NULL); /* member->var_name can be NULL */ - if (dwarf_diename(die)) - member->var_name = strdup(dwarf_diename(die)); + if (dwarf_diename(die)) { + if (bit_size) { + if (asprintf(&member->var_name, "%s:%ld", + dwarf_diename(die), (long)bit_size) < 0) + member->var_name = NULL; + } else { + member->var_name = strdup(dwarf_diename(die)); + } + + if (member->var_name == NULL) { + free(member); + return DIE_FIND_CB_END; + } + } member->size = size; member->offset = loc + parent->offset; INIT_LIST_HEAD(&member->children); -- 2.50.1