For cases where the compiler doesn't emits the whole struct definition for
things like base classes that don't have any of its members acessed, just the
ones in its descendants.
Will be used to avoid emiting hole anottations, since we don't have the
size of these classes we can't say if its smaller than the space allocated
by the compiler.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This new function searches the first member before the one being traversed that
has a bit hole (or byte_hole, I've just normalised it on bits to make it
generic) that can be used to combine with the class_member at hand to possibly
kill a hole, possibly because for now it doesn't guarantees that moving the
member being traversed to just after the hole after the member returned by
class__find_bit_hole will indeed reduce the struct size, but its a good first
stab, next csets should provide a member to start from so that we can try to
find other holes after the one that proved not enough to reduce the struct
size.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
To simplify the callsites and make implementing the same thing on the other
dwarves (prefcnt, pfunct, etc) easy.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
To represent DW_TAG_lexical_block, for now just group the lists of
labels, inline expansions and variables, struct function now has
the root of the tree as ->lexblock.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Introducing function__print_body, that orders the tags in a function by the
souce code line where it was declared or inlined.
This finally takes advantage of the struct tag "superclass", more to come in
the form of lexical blocks and goto labels.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Following what is in the DWARF2 specs:
Name Meaning
-----------------------------------------------------------------------------
DW_INL_not_inlined Not declared inline nor inlined by the compiler
DW_INL_inlined Not declared inline but inlined by the compiler
DW_INL_declared_not_inlined Declared inline but not inlined by the compiler
DW_INL_declared_inlined Declared inline and inlined by the compiler
Take advantae of this and use it in a new pfunct option: --cc_inlined, to
show which functions were of the DW_INL_inlined type.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
And helper routines, so as to separate DW_TAG_subprogram from
the type tags (DW_TAG_structure_type, basic_type, etc).
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This should have been done from the start: all DW_TAG_s will be represented by
structs that has as its first member a struct tag, so that we can fully
represent the DWARF information, following csets will take continue the
restructuring.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
That uses the DW_AT_external attribute, that tells if the DW_TAG_subprogram
(a function) is visible externally.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This fixes a problem with codiff usage of the ->class_to_diff member, as we
were looking at a different CU than the one intended, so we'd have to have a
pointer to the CU associated with ->class_to_diff, heck, its time to have this
backpointer :-)
Now to audit the rest of the code to look for simplifications since we now have
this backpointer and thus don't need to pass CU pointers around.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
[acme@newtoy examples]$ cat struct.c
static struct foo {
char a:2;
unsigned int b;
unsigned long c;
unsigned long d;
unsigned long e;
} bar;
int main(int argc, char *argv[])
{
printf("%d", bar.a);
}
[acme@newtoy examples]$
Then change "a:2" to "a:4":
[acme@newtoy examples]$ codiff -V old_struct new_struct
struct.c:
struct foo | +0
a:2;
from: char /* 0(6) 1(2) */
to: char /* 0(4) 1(4) */
1 struct changed
Now, on top of that move a after b:
[acme@newtoy examples]$ codiff -V old_struct new_struct
struct.c:
struct foo | +0
a:2;
from: char /* 0(6) 1(2) */
to: char /* 4(4) 1(4) */
b;
from: unsigned int /* 4(0) 4(0) */
to: unsigned int /* 0(0) 4(0) */
1 struct changed
[acme@newtoy examples]$
Move it back a to before b and change the type of e without changing its size,
i.e. from unsigned long to long:
[acme@newtoy examples]$ codiff -V old_struct new_struct
struct.c:
struct foo | +0
a:2;
from: char /* 0(6) 1(2) */
to: char /* 0(4) 1(4) */
e;
from: long unsigned int /* 16(0) 4(0) */
to: long int /* 16(0) 4(0) */
1 struct changed
[acme@newtoy examples]$
Now on top of this lets delete the c member:
[acme@newtoy examples]$ codiff -V old_struct new_struct
struct.c:
struct foo | -4
nr_members: -1
-long unsigned int c; /* 8 4 */
a:2;
from: char /* 0(6) 1(2) */
to: char /* 0(4) 1(4) */
d;
from: long unsigned int /* 12(0) 4(0) */
to: long unsigned int /* 8(0) 4(0) */
e;
from: long unsigned int /* 16(0) 4(0) */
to: long int /* 12(0) 4(0) */
1 struct changed
[acme@newtoy examples]$
WOW, many changes, what an ABI breakage, no? :-)
It started as:
[acme@newtoy examples]$ pahole old_struct foo
/* /home/acme/pahole/examples/struct.c:3 */
struct foo {
char a:2; /* 0 1 */
/* XXX 3 bytes hole, try to pack */
unsigned int b; /* 4 4 */
long unsigned int c; /* 8 4 */
long unsigned int d; /* 12 4 */
long unsigned int e; /* 16 4 */
}; /* size: 20, sum members: 17, holes: 1, sum holes: 3 */
And ended up as:
[acme@newtoy examples]$ pahole new_struct foo
/* /home/acme/pahole/examples/struct.c:3 */
struct foo {
char a:4; /* 0 1 */
/* XXX 3 bytes hole, try to pack */
unsigned int b; /* 4 4 */
long unsigned int d; /* 8 4 */
long int e; /* 12 4 */
}; /* size: 16, sum members: 13, holes: 1, sum holes: 3 */
[acme@newtoy examples]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
First step:
Show if struct members were removed or added:
[acme@newtoy net-2.6.20]$ codiff -sV /tmp/ipv6.ko.before /tmp/ipv6.ko.after
<SNIP>
/pub/scm/linux/kernel/git/acme/net-2.6.20/net/ipv6/tcp_ipv6.c:
struct inet_sock | -4
nr_members: -1
struct inet_connection_sock | -4
struct tcp_sock | -4
struct tcp6_sock | -4
4 structs changed
<SNIP>
Oh, so struct inet_sock must be one of the members of the other structs that
haven't had changes in its number of members? Yes, this is the case :-)
Now lets see _which_ members were removed, added or had its type changed
causing a reduction in the struct size.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
prefcnt is a new tool to do reference counting on all the TAGs, starting
from the list of DW_TAG_subroutine tags and going down thru the return type,
parameter list types, variables and inline expansions in the functions, to
help finding unused stuff, its not so effective because of bugs in gcc
DWARF emitting code for concrete inline instances, i.e. the inline expansions
are not all being emitted, see:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29792
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
To represent DW_TAG_variable, for now all the variables in all the lexical
blocks, in addition to the top level function variables are in this list, next
step is to add support for DW_TAG_lexical_block, with support for nesting, and
to associate variables to the right place, be it the function itself (first,
implicit lexical block) or to the lexical blocks they belong too, this will be
useful for calculating stack usage.
So, with what we have now pfunct can do this:
[acme@newtoy guinea_pig-2.6]$ pfunct --variables net/ipv4/built-in.o tcp_v4_remember_stamp
/* net/ipv4/tcp_ipv4.c:1197 */
int tcp_v4_remember_stamp(struct sock * sk);
{
/* variables in tcp_v4_remember_stamp: */
struct inet_sock * inet;
struct tcp_sock * tp;
struct rtable * rt;
struct inet_peer * peer;
int release_it;
}
[acme@newtoy guinea_pig-2.6]$
That is already useful when you don't have the sources, huh? :-)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Now it shows the number that each of the inline functions were expanded in an
object file:
Top 10 inline functions expanded more than once in kernel/sched.o, by total
size of inline expansions:
[acme@newtoy guinea_pig-2.6]$ pfunct --cu_inline_expansions_stats kernel/sched.o | sort -k3 -nr | grep -v ': 1 ' | head -11
kernel/sched.c: 318 10217
get_current: 38 325
finish_task_switch: 2 238
normal_prio: 2 167
__cpus_and: 14 164
find_process_by_pid: 6 152
current_thread_info: 21 149
sched_find_first_bit: 2 148
update_cpu_clock: 2 140
task_rq_unlock: 14 137
variable_test_bit: 14 121
[acme@newtoy guinea_pig-2.6]$
Now we have these options:
[acme@newtoy guinea_pig-2.6]$ pfunct --help
usage: pfunct [options] <file_name> {<function_name>}
where:
-c, --class=<class> functions that have <class> pointer parameters
-g, --goto_labels show number of goto labels
-i, --show_inline_expansions show inline expansions
-C, --cu_inline_expansions_stats show CU inline expansions stats
-s, --sizes show size of functions
-N, --function_name_len show size of functions
-p, --nr_parameters show number or parameters
-S, --variables show number of variables
-V, --verbose be verbose
[acme@newtoy guinea_pig-2.6]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Top five object files (CU, Compilation Unit) per number of inline expansions,
vmlinux being dissected is one built for QEMU, most things as modules, that
are not being taken into account as we're only looking at vmlinux:
[acme@newtoy guinea_pig-2.6]$ pfunct -C ../../acme/OUTPUT/qemu/net-2.6/vmlinux | sort -k2 -nr | head -5 | cut -c40-
net/ipv4/tcp_input.c: 274 20655
fs/buffer.c: 272 4597
kernel/sched.c: 214 3549
kernel/signal.c: 196 2730
fs/ext3/inode.c: 191 7961
[acme@newtoy guinea_pig-2.6]$
Top five object files (CU, Compilation Unit) per total size of inline expansions:
[acme@newtoy guinea_pig-2.6]$ pfunct -C ../../acme/OUTPUT/qemu/net-2.6/vmlinux | sort -k3 -nr | head -5 | cut -c40-
net/ipv4/tcp_input.c: 274 20655
net/xfrm/xfrm_policy.c: 173 11511
kernel/module.c: 95 10826
drivers/char/vt.c: 91 10050
net/xfrm/xfrm_user.c: 150 9682
[acme@newtoy guinea_pig-2.6]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Reducing the memory footprint, but more has to be done, such as to take
advantage of the strings table when handling indirect strings.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
So that we can find all the cus for some specific class
(cus__find_class_by_name), or traverse all the CUs (cus__for_each_cu),
etc.
Now we don't look at just the first CU in multi-CU files (vmlinux, etc).
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
types for each CU, for now when working on multi-CU files (vmlinux, any binary
with more than one object file linked) we look only at the first CU when
looking for a specific class or function name, this will be fixed in the
upcoming csets, but doesn't affect the case when we don't specify a class or
function name, where all the CU's are traversed.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
so that one can traverse all the classes loaded by classes__load.
Also export classes__find_by_id().
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
see that the function was indeed inlined:
[acme@newtoy net-2.6]$ pfunct kernel/sched.o task_running
/* /pub/scm/linux/kernel/git/acme/net-2.6/kernel/sched.c 304 */
inline int task_running(struct rq * rq, struct task_struct * p);
[acme@newtoy net-2.6]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
print just the structs with holes, that indeed is what we do now if no class
name is passed.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Arnaldo Carvalho de Melo
Johannes Berg