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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 <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240815223823.2402285-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim
Arnaldo Carvalho de Melo
parent
6236ebe071
commit
8b1042c425
1 changed files with 28 additions and 6 deletions
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@ -202,7 +202,7 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
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struct annotated_member *parent = arg;
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struct annotated_member *member;
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Dwarf_Die member_type, die_mem;
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Dwarf_Word size, loc;
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Dwarf_Word size, loc, bit_size = 0;
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Dwarf_Attribute attr;
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struct strbuf sb;
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int tag;
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@ -226,15 +226,37 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
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if (dwarf_aggregate_size(&die_mem, &size) < 0)
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size = 0;
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if (!dwarf_attr_integrate(die, DW_AT_data_member_location, &attr))
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loc = 0;
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else
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if (dwarf_attr_integrate(die, DW_AT_data_member_location, &attr))
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dwarf_formudata(&attr, &loc);
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else {
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/* bitfield member */
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if (dwarf_attr_integrate(die, DW_AT_data_bit_offset, &attr) &&
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dwarf_formudata(&attr, &loc) == 0)
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loc /= 8;
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else
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loc = 0;
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if (dwarf_attr_integrate(die, DW_AT_bit_size, &attr) &&
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dwarf_formudata(&attr, &bit_size) == 0)
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size = (bit_size + 7) / 8;
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}
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member->type_name = strbuf_detach(&sb, NULL);
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/* member->var_name can be NULL */
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if (dwarf_diename(die))
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member->var_name = strdup(dwarf_diename(die));
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if (dwarf_diename(die)) {
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if (bit_size) {
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if (asprintf(&member->var_name, "%s:%ld",
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dwarf_diename(die), (long)bit_size) < 0)
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member->var_name = NULL;
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} else {
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member->var_name = strdup(dwarf_diename(die));
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}
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if (member->var_name == NULL) {
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free(member);
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return DIE_FIND_CB_END;
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}
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}
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member->size = size;
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member->offset = loc + parent->offset;
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INIT_LIST_HEAD(&member->children);
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