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libsymbols kallsyms: Parse using io api

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'perf record' will call kallsyms__parse 4 times during startup and
process megabytes of data. This changes kallsyms__parse to use the io
library rather than fgets to improve performance of the user code by
over 8%.

Before:

  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 103.988 ms (+- 0.203 ms)

After:

  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 95.571 ms (+- 0.006 ms)

For a workload like:

  $ perf record /bin/true
  Run under 'perf record -e cycles:u -g' the time goes from:
  Before
  30.10%     1.67%  perf     perf                [.] kallsyms__parse
  After
  25.55%    20.04%  perf     perf                [.] kallsyms__parse

So a little under 5% of the start-up time is removed. A lot of what
remains is on the kernel side, but caching kallsyms within perf would at
least impact memory footprint.

Committer notes:

The internal/kallsyms-parse bench is run using:

  [root@five ~]# perf bench internals kallsyms-parse
  # Running 'internals/kallsyms-parse' benchmark:
    Average kallsyms__parse took: 80.381 ms (+- 0.115 ms)
  [root@five ~]#

And this pre-existing test uses these routines to parse kallsyms and
then compare with the info obtained from the matching ELF symtab:

  [root@five ~]# perf test vmlinux
   1: vmlinux symtab matches kallsyms                       : Ok
  [root@five ~]#

Also we can't remove hex2u64() in this patch as this breaks the build:

  /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `modules__parse':
  /home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
  /usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
  /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `dso__load_perf_map':
  /home/acme/git/perf/tools/perf/util/symbol.c:1477: undefined reference to `hex2u64'
  /usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:1483: undefined reference to `hex2u64'
  collect2: error: ld returned 1 exit status

Leave it there, move it in the next patch.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200501221315.54715-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2020-05-01 15:13:14 -07:00 committed by Arnaldo Carvalho de Melo
parent 51876bd452
commit 53df2b9344
2 changed files with 52 additions and 46 deletions
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3
tools/lib/api/io.h
View File

@ -7,6 +7,9 @@
#ifndef __API_IO__
#define __API_IO__
#include <stdlib.h>
#include <unistd.h>
struct io {
/* File descriptor being read/ */
int fd;

95
tools/lib/symbol/kallsyms.c
View File

@ -1,7 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
#include "symbol/kallsyms.h"
#include "api/io.h"
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
u8 kallsyms2elf_type(char type)
{
@ -9,12 +11,6 @@ u8 kallsyms2elf_type(char type)
return (type == 't' || type == 'w') ? STT_FUNC : STT_OBJECT;
}
bool kallsyms__is_function(char symbol_type)
{
symbol_type = toupper(symbol_type);
return symbol_type == 'T' || symbol_type == 'W';
}
/*
* While we find nice hex chars, build a long_val.
* Return number of chars processed.
@ -28,61 +24,68 @@ int hex2u64(const char *ptr, u64 *long_val)
return p - ptr;
}
bool kallsyms__is_function(char symbol_type)
{
symbol_type = toupper(symbol_type);
return symbol_type == 'T' || symbol_type == 'W';
}
static void read_to_eol(struct io *io)
{
int ch;
for (;;) {
ch = io__get_char(io);
if (ch < 0 || ch == '\n')
return;
}
}
int kallsyms__parse(const char *filename, void *arg,
int (*process_symbol)(void *arg, const char *name,
char type, u64 start))
{
char *line = NULL;
size_t n;
int err = -1;
FILE *file = fopen(filename, "r");
struct io io;
char bf[BUFSIZ];
int err;
if (file == NULL)
goto out_failure;
io.fd = open(filename, O_RDONLY, 0);
if (io.fd < 0)
return -1;
io__init(&io, io.fd, bf, sizeof(bf));
err = 0;
while (!feof(file)) {
u64 start;
int line_len, len;
while (!io.eof) {
__u64 start;
int ch;
size_t i;
char symbol_type;
char *symbol_name;
char symbol_name[KSYM_NAME_LEN + 1];
line_len = getline(&line, &n, file);
if (line_len < 0 || !line)
break;
line[--line_len] = '\0'; /* \n */
len = hex2u64(line, &start);
/* Skip the line if we failed to parse the address. */
if (!len)
if (io__get_hex(&io, &start) != ' ') {
read_to_eol(&io);
continue;
len++;
if (len + 2 >= line_len)
continue;
symbol_type = line[len];
len += 2;
symbol_name = line + len;
len = line_len - len;
if (len >= KSYM_NAME_LEN) {
err = -1;
break;
}
symbol_type = io__get_char(&io);
if (io__get_char(&io) != ' ') {
read_to_eol(&io);
continue;
}
for (i = 0; i < sizeof(symbol_name); i++) {
ch = io__get_char(&io);
if (ch < 0 || ch == '\n')
break;
symbol_name[i] = ch;
}
symbol_name[i] = '\0';
err = process_symbol(arg, symbol_name, symbol_type, start);
if (err)
break;
}
free(line);
fclose(file);
close(io.fd);
return err;
out_failure:
return -1;
}