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* [binutils-gdb] add splay tree for info_ptr -> CU mapping
@ 2022-08-08 11:52 Martin Liska
0 siblings, 0 replies; only message in thread
From: Martin Liska @ 2022-08-08 11:52 UTC (permalink / raw)
To: bfd-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e441b55e94c905c6ee4417be3e5d88021d9c5aa6
commit e441b55e94c905c6ee4417be3e5d88021d9c5aa6
Author: Martin Liska <mliska@suse.cz>
Date: Wed Aug 3 11:28:10 2022 +0200
add splay tree for info_ptr -> CU mapping
While using perf top for MozillaThunderbird I noticed quite some slow
dissably call with source code involved. E.g.
time ./objdump --start-address=0x0000000004e0dcd0 --stop-address=0x0000000004e0df8b -l -d --no-show-raw-insn -S -C /usr/lib64/thunderbird/libxul.so
took 2.071s and I noticed quite some time is spent in
find_abstract_instance:
33.46% objdump objdump [.] find_abstract_instance
18.22% objdump objdump [.] arange_add
13.77% objdump objdump [.] read_attribute_value
4.82% objdump objdump [.] comp_unit_maybe_decode_line_info
3.10% objdump libc.so.6 [.] __memset_avx2_unaligned_erms
where linked list of CU is iterated when searing for where info_ptr
belongs to:
: 3452 for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
0.00 : 4c61f7: mov 0x10(%rbx),%rax
0.00 : 4c61fb: test %rax,%rax
0.00 : 4c61fe: je 4c6215 <find_abstract_instance+0x365>
: 3453 if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
0.00 : 4c6200: cmp 0x60(%rax),%rdx
83.20 : 4c6204: jb 4c620c <find_abstract_instance+0x35c>
0.00 : 4c6206: cmp 0x78(%rax),%rdx
6.89 : 4c620a: jb 4c6270 <find_abstract_instance+0x3c0>
: 3452 for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
0.00 : 4c620c: mov 0x10(%rax),%rax
7.90 : 4c6210: test %rax,%rax
0.00 : 4c6213: jne 4c6200 <find_abstract_instance+0x350>
The following scan can be replaced with search in a splay tree and with
that I can get to 1.5s and there are other symbols where the difference
is even bigger.
bfd/ChangeLog:
PR 29081
* dwarf2.c (struct addr_range): New.
(addr_range_intersects): Likewise.
(splay_tree_compare_addr_range): Likewise.
(splay_tree_free_addr_range): Likewise.
(struct dwarf2_debug_file): Add comp_unit_tree.
(find_abstract_instance): Use the splay tree when searching
for a info_ptr.
(stash_comp_unit): Insert to the splay tree.
(_bfd_dwarf2_cleanup_debug_info): Clean up the splay tree.
Diff:
---
bfd/dwarf2.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 67 insertions(+), 10 deletions(-)
diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index fbe9dd2070b..69d30216771 100644
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -36,6 +36,7 @@
#include "elf-bfd.h"
#include "dwarf2.h"
#include "hashtab.h"
+#include "splay-tree.h"
/* The data in the .debug_line statement prologue looks like this. */
@@ -152,6 +153,45 @@ static struct trie_node *alloc_trie_leaf (bfd *abfd)
return &leaf->head;
}
+struct addr_range
+{
+ bfd_byte *start;
+ bfd_byte *end;
+};
+
+/* Return true if address range do intersect. */
+
+static bool
+addr_range_intersects (struct addr_range *r1, struct addr_range *r2)
+{
+ return (r1->start <= r2->start && r2->start < r1->end)
+ || (r1->start <= (r2->end - 1) && (r2->end - 1) < r1->end);
+}
+
+/* Compare function for splay tree of addr_ranges. */
+
+static int
+splay_tree_compare_addr_range (splay_tree_key xa, splay_tree_key xb)
+{
+ struct addr_range *r1 = (struct addr_range *) xa;
+ struct addr_range *r2 = (struct addr_range *) xb;
+
+ if (addr_range_intersects (r1, r2) || addr_range_intersects (r2, r1))
+ return 0;
+ else if (r1->end <= r2->start)
+ return -1;
+ else
+ return 1;
+}
+
+/* Splay tree release function for keys (addr_range). */
+
+static void
+splay_tree_free_addr_range (splay_tree_key key)
+{
+ free ((struct addr_range *)key);
+}
+
struct dwarf2_debug_file
{
/* The actual bfd from which debug info was loaded. Might be
@@ -235,6 +275,9 @@ struct dwarf2_debug_file
/* Root of a trie to map addresses to compilation units. */
struct trie_node *trie_root;
+
+ /* Splay tree to map info_ptr address to compilation units. */
+ splay_tree comp_unit_tree;
};
struct dwarf2_debug
@@ -3447,16 +3490,12 @@ find_abstract_instance (struct comp_unit *unit,
else
{
/* Check other CUs to see if they contain the abbrev. */
- struct comp_unit *u;
-
- for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
- if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
- break;
-
- if (u == NULL)
- for (u = unit->next_unit; u != NULL; u = u->next_unit)
- if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
- break;
+ struct comp_unit *u = NULL;
+ struct addr_range range = { info_ptr, info_ptr };
+ splay_tree_node v = splay_tree_lookup (unit->file->comp_unit_tree,
+ (splay_tree_key)&range);
+ if (v != NULL)
+ u = (struct comp_unit *)v->value;
if (attr_ptr->form == DW_FORM_ref_addr)
while (u == NULL)
@@ -5509,6 +5548,22 @@ stash_comp_unit (struct dwarf2_debug *stash, struct dwarf2_debug_file *file)
info_ptr_unit, offset_size);
if (each)
{
+ if (file->comp_unit_tree == NULL)
+ file->comp_unit_tree
+ = splay_tree_new (splay_tree_compare_addr_range,
+ splay_tree_free_addr_range, NULL);
+
+ struct addr_range *r
+ = (struct addr_range *)bfd_malloc (sizeof (struct addr_range));
+ r->start = each->info_ptr_unit;
+ r->end = each->end_ptr;
+ splay_tree_node v = splay_tree_lookup (file->comp_unit_tree,
+ (splay_tree_key)r);
+ if (v != NULL || r->end <= r->start)
+ abort ();
+ splay_tree_insert (file->comp_unit_tree, (splay_tree_key)r,
+ (splay_tree_value)each);
+
if (file->all_comp_units)
file->all_comp_units->prev_unit = each;
else
@@ -5982,6 +6037,8 @@ _bfd_dwarf2_cleanup_debug_info (bfd *abfd, void **pinfo)
free (file->line_table->dirs);
}
htab_delete (file->abbrev_offsets);
+ if (file->comp_unit_tree != NULL)
+ splay_tree_delete (file->comp_unit_tree);
free (file->dwarf_line_str_buffer);
free (file->dwarf_str_buffer);
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2022-08-08 11:52 [binutils-gdb] add splay tree for info_ptr -> CU mapping Martin Liska
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