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dwarves: Revert semantics of member bit/byte hole 

pahole --reorganize heavily depends on member's bit_hole and hole fields
to denote bit/byte holes *after* member. Previous commit "dwarves: use
bit sizes and bit/byte hole info in __class__fprintf" changed its
meaning to bit/byte hole *before* member to accomodate possible bit/byte
holes at the beginning of a struct. This change broke reorganization
algorithm, though, which is quite involved and isn't trivially
modifiable to accomodate new semantics.

This patch reverts the meaning of bit_hole and hole, but also introduces
per class pre_bit_hole/pre_hole to record initial bit/byte hole of a
struct. This allows to fix reorg code more easily and still handle
initial holes cases, if at the expense of being not as elegant.

Committer testing:

  $ time pahole -F btf --packable vmlinux | sort -nr -k4 | head
  bts_ctx     12288 8192 4096
  swsusp_info  4096  432 3664
  vc_data       792  496  296
  pci_dev      2488 2320  168
  rcu_state    3392 3240  152
  ptr_ring      192   40  152
  xdp_sock      960  840  120
  zone         1664 1552  112
  rcu_data      576  472  104
  rcu_node      576  480   96

  real	0m0.038s
  user	0m0.029s
  sys	0m0.017s
  $

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Andrii Nakryiko 2019-04-03 00:01:45 -07:00 committed by Arnaldo Carvalho de Melo
parent b56fed297e
commit 78c110a7ea
3 changed files with 57 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
dwarves.c
View File

@ -1260,8 +1260,13 @@ void class__find_holes(struct class *class)
cur_bitfield_end = bit_end;
}
pos->hole = byte_holes;
pos->bit_hole = bit_holes;
if (last) {
last->hole = byte_holes;
last->bit_hole = bit_holes;
} else {
class->pre_hole = byte_holes;
class->pre_bit_hole = bit_holes;
}
if (bit_holes)
class->nr_bit_holes++;
if (byte_holes)

2
dwarves.h
View File

@ -1026,7 +1026,9 @@ struct class {
uint16_t nr_vtable_entries;
uint8_t nr_holes;
uint8_t nr_bit_holes;
uint16_t pre_hole;
uint16_t padding;
uint8_t pre_bit_hole;
uint8_t bit_padding;
bool holes_searched;
void *priv;

72
dwarves_fprintf.c
View File

@ -1292,6 +1292,30 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu,
printed += fprintf(fp, " {\n");
if (class->pre_bit_hole > 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "%.*s/* XXX %d bit%s hole, "
"try to pack */\n", cconf.indent, tabs,
class->pre_bit_hole,
class->pre_bit_hole != 1 ? "s" : "");
sum_bit_holes += class->pre_bit_hole;
}
if (class->pre_hole > 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "%.*s/* XXX %d byte%s hole, "
"try to pack */\n",
cconf.indent, tabs, class->pre_hole,
class->pre_hole != 1 ? "s" : "");
sum_holes += class->pre_hole;
}
type__for_each_tag(type, tag_pos) {
struct tag *type;
const char *accessibility = tag__accessibility(tag_pos);
@ -1361,30 +1385,6 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu,
}
}
if (pos->bit_hole != 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "%.*s/* XXX %d bit%s hole, "
"try to pack */\n", cconf.indent, tabs,
pos->bit_hole,
pos->bit_hole != 1 ? "s" : "");
sum_bit_holes += pos->bit_hole;
}
if (pos->hole > 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "%.*s/* XXX %d byte%s hole, "
"try to pack */\n",
cconf.indent, tabs, pos->hole,
pos->hole != 1 ? "s" : "");
sum_holes += pos->hole;
}
if (newline) {
fputc('\n', fp);
newline = 0;
@ -1428,6 +1428,30 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu,
}
}
if (pos->bit_hole != 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "\n%.*s/* XXX %d bit%s hole, "
"try to pack */", cconf.indent, tabs,
pos->bit_hole,
pos->bit_hole != 1 ? "s" : "");
sum_bit_holes += pos->bit_hole;
}
if (pos->hole > 0 && !cconf.suppress_comments) {
if (!newline++) {
fputc('\n', fp);
++printed;
}
printed += fprintf(fp, "\n%.*s/* XXX %d byte%s hole, "
"try to pack */",
cconf.indent, tabs, pos->hole,
pos->hole != 1 ? "s" : "");
sum_holes += pos->hole;
}
fputc('\n', fp);
++printed;