Re: [PATCH v1 01/14] perf util: Create source line mapping table

From: Arnaldo Carvalho de Melo
Date: Tue Mar 10 2020 - 11:09:02 EST

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In reply to: Jin Yao: "[PATCH v1 01/14] perf util: Create source line mapping table"
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Em Tue, Mar 10, 2020 at 03:02:32PM +0800, Jin Yao escreveu:
> Sometimes, a small change in a hot function reducing the cycles of
> this function, but the overall workload doesn't get faster. It is
> interesting where the cycles are moved to.
>
> What it would like is to diff before/after streams. A stream is a
> callchain which is aggregated by the branch records from samples.
>
> By browsing the hot streams, we can understand the hot code flow.
> By comparing the cycles variation of same streams between old perf
> data and new perf data, we can understand if the cycles are moved to
> the unchanged code.
>
> The before stream is the stream before source line changed
> (e.g. streams in perf.data.old). The after stream is the stream
> after source line changed (e.g. streams in perf.data).
>
> Diffing before/after streams compares all streams (or compares top
> N hot streams) between two perf data files.
>
> If all entries of one stream in perf.data.old are fully matched with
> all entries of another stream in perf.data, we think these two streams
> are matched, otherwise the streams are not matched.
>
> For example,
>
> cycles: 1, hits: 26.80% cycles: 1, hits: 27.30%
> -------------------------- --------------------------
> main div.c:39 main div.c:39
> main div.c:44 main div.c:44
>
> It looks that two streams are matched and we can see for the same
> streams the cycles are equal and the stream hit percents are
> slightly changed. That's expected in the normal range.
>
> But that's not always true if source lines are changed in perf.data
> (e.g. div.c:39 is changed). If the source line is changed, they
> are different streams, we can't compare them. We just think the
> stream in perf.data is a new one.
>
> The challenge is how to identify the changed source lines. The basic
> idea is to use linux command 'diff' to compare the source file A and
> source file A* line by line (assume A is used in perf.data.old
> and A* is updated in perf.data). Create a source line mapping table.
>
> For example,
>
> Execute 'diff ./before/div.c ./after/div.c'
>
> 25c25
> < i = rand() % 2;
> ---
> > i = rand() % 4;
> 39c39
> < for (i = 0; i < 2000000000; i++) {
> ---
> > for (i = 0; i < 20000000001; i++) {
>
> div.c (after -> before) lines mapping:
> 0 -> 0
> 1 -> 1
> 2 -> 2
> 3 -> 3
> 4 -> 4
> 5 -> 5
> 6 -> 6
> 7 -> 7
> 8 -> 8
> 9 -> 9
> ...
> 24 -> 24
> 25 -> -1
> 26 -> 26
> 27 -> 27
> 28 -> 28
> 29 -> 29
> 30 -> 30
> 31 -> 31
> 32 -> 32
> 33 -> 33
> 34 -> 34
> 35 -> 35
> 36 -> 36
> 37 -> 37
> 38 -> 38
> 39 -> -1
> 40 -> 40
> ...
>
> From the table, we can easily know div.c:39 is source line changed.
> (it's mapped to -1). So these two streams are not matched.
>
> This patch can also handle the cases of new source lines insertion
> and old source lines deletion. This source line mapping table is a
> base for next processing for stream comparison.
>
> This patch creates a new rblist 'srclist' to manage the source line
> mapping tables. Each node contains the source line mapping table of
> a before/after source file pair. The node is created on demand as
> we process the samples. So it's likely we don't need to create so many
> nodes.
>
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> ---
> tools/perf/util/Build | 1 +
> tools/perf/util/srclist.c | 552 ++++++++++++++++++++++++++++++++++++++
> tools/perf/util/srclist.h | 65 +++++
> 3 files changed, 618 insertions(+)
> create mode 100644 tools/perf/util/srclist.c
> create mode 100644 tools/perf/util/srclist.h
>
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index c0cf8dff694e..b9bf620b60f0 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -99,6 +99,7 @@ perf-y += call-path.o
> perf-y += rwsem.o
> perf-y += thread-stack.o
> perf-y += spark.o
> +perf-y += srclist.o
> perf-$(CONFIG_AUXTRACE) += auxtrace.o
> perf-$(CONFIG_AUXTRACE) += intel-pt-decoder/
> perf-$(CONFIG_AUXTRACE) += intel-pt.o
> diff --git a/tools/perf/util/srclist.c b/tools/perf/util/srclist.c
> new file mode 100644
> index 000000000000..cb1d42a3a8ed
> --- /dev/null
> +++ b/tools/perf/util/srclist.c
> @@ -0,0 +1,552 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Manage difference of source lines
> + * Copyright (c) 2020, Intel Corporation.
> + * Author: Jin Yao
> + */
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <inttypes.h>
> +#include <string.h>
> +#include <strings.h>
> +#include <unistd.h>
> +#include <err.h>
> +#include <errno.h>
> +#include <limits.h>
> +#include <stdbool.h>
> +#include <linux/zalloc.h>
> +#include "strlist.h"
> +#include "srclist.h"
> +#include "debug.h"
> +
> +enum {
> + DIFF_LINE_ADD,
> + DIFF_LINE_DEL,
> + DIFF_LINE_CHANGE
> +};
> +
> +static void get_full_path(const char *dir, const char *rel_path,
> + char *full_path, int size)
> +{
> + if (!dir) {
> + snprintf(full_path, size, "%s", rel_path);
> + return;
> + }
> +
> + if (dir[strlen(dir) - 1] == '/')
> + snprintf(full_path, size, "%s%s", dir, rel_path);
> + else
> + snprintf(full_path, size, "%s/%s", dir, rel_path);

Just use

snprintf(full_path, size, "%s/%s", dir, rel_path);

an extra / won't matter, the code will be smaller. At first I thought
you could use path__join(), please check if that is the case.

> +}
> +
> +static int get_line_num(char *path)

So this is to get how many lines a given file has? I.e. 'wc -l'? Maybe:

static int path__number_of_lines(const char *path)

?

> +{
> + FILE *fh;
> + int num = 0, ch, last = 0;
> +
> + fh = fopen(path, "r");
> + if (!fh) {
> + pr_debug("Failed to open file %s\n", path);
> + return -1;
> + }
> +
> + while (!feof(fh)) {
> + ch = fgetc(fh);
> + if (ch == '\n')
> + num++;
> + last = ch;

Maybe use fgets() instead as it already stops at '\n'?

> + }
> +
> + fclose(fh);
> +
> + if (last != '\n')
> + num++;
> +
> + return num;
> +}
> +
> +static int get_digit(char *str, char **end_str, int *val)
> +{
> + int v;
> + char *end;
> +
> + errno = 0;
> + v = strtol(str, &end, 10);
> + if ((errno == ERANGE && (v == INT_MAX || v == INT_MIN))
> + || (errno != 0 && v == 0)) {
> + return -1;
> + }
> +
> + if (end == str)
> + return -1;
> +
> + *val = v;
> + *end_str = end;
> + return 0;
> +}
> +
> +static int get_range(char *str, int *start_val, int *end_val)
> +{
> + int val, ret;
> + char *end, *next;
> +
> + *start_val = -1;
> + *end_val = -1;
> +
> + ret = get_digit(str, &end, &val);
> + if (ret)
> + return ret;
> +
> + *start_val = val;
> +
> + if (*end != '\0') {
> + next = end + 1;
> + ret = get_digit(next, &end, &val);
> + if (ret)
> + return ret;
> +
> + *end_val = val;
> + }
> +
> + return 0;
> +}
> +
> +static int opr_str_idx(char *str, int len, char ch)
> +{
> + int i;
> +
> + for (i = 0; i < len; i++) {
> + if (str[i] == ch)
> + break;
> + }
> +
> + if (i == len || i == 0 || i == len - 1)
> + return -1;
> +
> + if (str[i - 1] >= '0' && str[i - 1] <= '9' &&
> + str[i + 1] >= '0' && str[i + 1] <= '9') {
> + return i;
> + }
> +
> + return -1;
> +}
> +
> +static bool get_diff_operation(char *str, int *opr, int *b_start, int *b_end,
> + int *a_start, int *a_end)
> +{
> + int idx, len;
> +
> + if (str[0] == '<' || str[0] == '>' || str[0] == '-')
> + return false;
> +
> + len = strlen(str);
> +
> + /*
> + * For example,
> + * 5,6d4
> + * 8a7
> + * 20,21c19
> + */
> + idx = opr_str_idx(str, len, 'd');
> + if (idx != -1) {
> + *opr = DIFF_LINE_DEL;
> + goto exit;
> + }
> +
> + idx = opr_str_idx(str, len, 'a');
> + if (idx != -1) {
> + *opr = DIFF_LINE_ADD;
> + goto exit;
> + }
> +
> + idx = opr_str_idx(str, len, 'c');
> + if (idx != -1) {
> + *opr = DIFF_LINE_CHANGE;
> + goto exit;
> + }
> +
> +exit:
> + if (idx != -1) {
> + str[idx] = 0;
> + get_range(str, b_start, b_end);
> + get_range(&str[idx + 1], a_start, a_end);

get_range() may return -1, don't you have to check this here?

> + return true;
> + }
> +
> + return false;
> +}
> +
> +static int del_lines(struct line_pair *lines, int b_start, int b_end,
> + int a_start, int a_end __maybe_unused,
> + int *nr_lines, int *b_adjust)
> +{
> + int i = *nr_lines;
> + bool set = false;
> +
> + /*
> + * For example, 5,6d4
> + * It means line5~line6 of file1 are not same as line4 of file2
> + * since line5~line6 are deleted.
> + */
> +
> + if (a_start == i) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = i + *b_adjust;
> + set = true;
> + }
> +
> + if (b_end != -1)
> + *b_adjust += b_end - b_start + 1;
> + else
> + *b_adjust += 1;
> +
> + if (!set) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = i + *b_adjust;
> + }
> +
> + *nr_lines = i + 1;
> + return 0;
> +}
> +
> +static int add_lines(struct line_pair *lines,
> + int b_start __maybe_unused, int b_end __maybe_unused,
> + int a_start, int a_end, int *nr_lines, int *b_adjust)
> +{
> + int i = *nr_lines;
> +
> + /*
> + * For example, 8a7
> + * It means line8 of file1 is not same as line7 of file2
> + * since a new line (line7) is inserted to file2.
> + */
> + if (a_end != -1) {
> + for (int j = 0; j < a_end - a_start + 1; j++) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = -1;
> + i++;
> + }
> + *b_adjust -= a_end - a_start + 1;
> + } else {
> + lines[i].a_nr = i;
> + lines[i].b_nr = -1;
> + i++;
> + *b_adjust -= 1;
> + }
> +
> + *nr_lines = i;
> + return 0;
> +}
> +
> +static int change_lines(struct line_pair *lines, int b_start, int b_end,
> + int a_start, int a_end, int *nr_lines, int *b_adjust)
> +{
> + int i = *nr_lines;
> +
> + /*
> + * For example, 20,21c19
> + * It means line20~line21 of file1 are not same as line19 of file2
> + * since they are changed.
> + */
> +
> + if (a_end != -1) {
> + for (int j = 0; j < a_end - a_start + 1; j++) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = -1;
> + i++;
> + }
> + } else {
> + lines[i].a_nr = i;
> + lines[i].b_nr = -1;
> + i++;
> + }
> +
> + if (b_end != -1)
> + *b_adjust += b_end - b_start;
> +
> + if (a_end != -1)
> + *b_adjust -= a_end - a_start;
> +
> + *nr_lines = i;
> + return 0;
> +}
> +
> +static int update_lines(struct line_pair *lines, int opr, int b_start,
> + int b_end, int a_start, int a_end, int *nr_lines,
> + int *b_adjust)

Functions operating on thisa 'struct line_pair' should have the
line_pair__ prefix, so that we can use ctags, etc, as we have other
places that process lines, etc, which may end up clashing.

> +{
> + int i = *nr_lines;
> +
> + while (i < a_start) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = i + *b_adjust;
> + i++;
> + }
> +
> + *nr_lines = i;
> +
> + switch (opr) {
> + case DIFF_LINE_DEL:
> + del_lines(lines, b_start, b_end, a_start, a_end,
> + nr_lines, b_adjust);
> + break;
> +
> + case DIFF_LINE_ADD:
> + add_lines(lines, b_start, b_end, a_start, a_end,
> + nr_lines, b_adjust);
> + break;
> +
> + case DIFF_LINE_CHANGE:
> + change_lines(lines, b_start, b_end, a_start, a_end,
> + nr_lines, b_adjust);
> + break;
> +
> + default:
> + break;
> + }
> +
> + return 0;
> +}
> +
> +static void update_remaining(struct line_pair *lines, int a_num, int *nr_lines,
> + int b_adjust)
> +{
> + int i;
> +
> + for (i = *nr_lines; i <= a_num; i++) {
> + lines[i].a_nr = i;
> + lines[i].b_nr = i + b_adjust;
> + }
> +
> + *nr_lines = i;
> +}
> +
> +static int build_mapping_table(FILE *diff_fd, struct line_pair *lines,
> + int *nr_lines, int a_num)
> +{
> + char *str, *p;
> + size_t len;
> + int opr, b_start, b_end, a_start, a_end, b_adjust = 0;
> +
> + *nr_lines = 1; /* First line is reserved */
> +
> + while (!feof(diff_fd)) {
> + str = NULL;

Forgot to set len to zero? (See getline manpage)

> + if (getline(&str, &len, diff_fd) < 0 || !len)
> + break;
> +
> + p = strchr(str, '\n');
> + if (p)
> + *p = '\0';
> +
> + pr_debug("%s\n", str);
> +
> + if (!get_diff_operation(str, &opr, &b_start, &b_end,
> + &a_start, &a_end)) {
> + continue;
> + }
> +
> + update_lines(lines, opr, b_start, b_end, a_start, a_end,
> + nr_lines, &b_adjust);

So, since str was allocated, where is it being kept? above you're always
setting it to NULL before calling getline.

> + }
> +
> + update_remaining(lines, a_num, nr_lines, b_adjust);
> +
> + free(str);
> + return 0;
> +}
> +
> +static int create_line_mapping(struct src_info *info, char *b_path,
> + char *a_path)

src_info__create_line_mappings() ?

> +{
> + char cmd[PATH_MAX];
> + FILE *diff_fd = NULL;
> + int ret = -1;
> +
> + info->nr_lines_before = get_line_num(b_path);
> + if (info->nr_lines_before == -1)
> + goto out;
> +
> + info->nr_lines_after = get_line_num(a_path);
> + if (info->nr_lines_after == -1)
> + goto out;
> +
> + /* Reserve first line */
> + info->nr_max = info->nr_lines_before + info->nr_lines_after + 1;
> + info->lines = calloc(info->nr_max, sizeof(struct line_pair));
> + if (!info->lines) {
> + pr_err("Failed to alloc memory for lines\n");
> + goto out;
> + }
> +
> + snprintf(cmd, sizeof(cmd), "diff %s %s",
> + b_path, a_path);
> +
> + pr_debug("Execute '%s'\n", cmd);
> +
> + diff_fd = popen(cmd, "r");
> + if (!diff_fd) {
> + pr_err("Failed to execute '%s'\n", cmd);
> + goto out;
> + }
> +
> + ret = build_mapping_table(diff_fd, info->lines, &info->nr_lines,
> + info->nr_lines_after);
> +
> +out:
> + if (diff_fd)
> + fclose(diff_fd);
> +
> + return ret;
> +}
> +
> +static void free_src_info(struct src_info *info)
> +{
> + if (info->rel_path)
> + zfree(&info->rel_path);
> +
> + if (info->lines)
> + zfree(&info->lines);

No need to check if it is NULL, call zfree() straight away.

> +}
> +
> +static int init_src_info(char *b_path, char *a_path, const char *rel_path,
> + struct src_info *info)
> +{
> + int ret;
> +
> + info->rel_path = strdup(rel_path);
> + if (!info->rel_path)
> + return -1;
> +
> + ret = create_line_mapping(info, b_path, a_path);
> + if (ret) {
> + free_src_info(info);
> + return ret;
> + }
> +
> + return 0;

if (ret)
free_src_info(info);

return ret;

Should be equivalent and shorter, no?

> +}
> +
> +static void free_src_node(struct src_node *node)
> +{

Free routines should accept a NULL arg, i.e. first thing:

if (node == NULL)
return;

> + free_src_info(&node->info);
> + free(node);
> +}
> +
> +static struct rb_node *srclist__node_new(struct rblist *rblist,
> + const void *entry)
> +{
> + struct srclist *slist = container_of(rblist, struct srclist, rblist);
> + const char *rel_path = entry;
> + char b_path[PATH_MAX], a_path[PATH_MAX];
> + struct src_node *node;
> + int ret;
> +
> + get_full_path(slist->before_dir, rel_path, b_path, PATH_MAX);
> + get_full_path(slist->after_dir, rel_path, a_path, PATH_MAX);
> +
> + node = calloc(1, sizeof(*node));

zalloc()?

> + if (!node)
> + return NULL;
> +
> + ret = init_src_info(b_path, a_path, rel_path, &node->info);
> + if (ret)
> + goto err;
> +
> + return &node->rb_node;
> +
> +err:
> + free_src_node(node);
> + return NULL;
> +}
> +
> +static void srclist__node_delete(struct rblist *rblist __maybe_unused,
> + struct rb_node *rb_node)
> +{
> + struct src_node *node = container_of(rb_node, struct src_node, rb_node);
> +
> + free_src_info(&node->info);
> + free(node);
> +}
> +
> +static int srclist__node_cmp(struct rb_node *rb_node, const void *entry)
> +{
> + struct src_node *node = container_of(rb_node, struct src_node, rb_node);
> + const char *str = entry;
> +
> + return strcmp(node->info.rel_path, str);
> +}
> +
> +struct srclist *srclist__new(const char *before_dir, const char *after_dir)
> +{
> + struct srclist *slist = calloc(1, sizeof(*slist));

zalloc()

> +
> + if (!slist)
> + return NULL;
> +
> + rblist__init(&slist->rblist);
> + slist->rblist.node_cmp = srclist__node_cmp;
> + slist->rblist.node_new = srclist__node_new;
> + slist->rblist.node_delete = srclist__node_delete;
> +
> + slist->before_dir = before_dir;
> + slist->after_dir = after_dir;
> + return slist;
> +}
> +
> +void srclist__delete(struct srclist *slist)
> +{
> + if (slist)
> + rblist__delete(&slist->rblist);

Correct, delete operations should accept NULL, just like free()

> +}
> +
> +struct src_node *srclist__find(struct srclist *slist, char *rel_path,
> + bool create)
> +{
> + struct src_node *node = NULL;
> + struct rb_node *rb_node;
> +
> + if (create)
> + rb_node = rblist__findnew(&slist->rblist, (void *)rel_path);
> + else
> + rb_node = rblist__find(&slist->rblist, (void *)rel_path);
> +
> + if (rb_node)
> + node = container_of(rb_node, struct src_node, rb_node);
> +
> + return node;
> +}
> +
> +struct line_pair *srclist__line_pair(struct src_node *node, int a_nr)
> +{
> + struct src_info *info = &node->info;
> +
> + if (a_nr < info->nr_lines && a_nr > 0)
> + return &info->lines[a_nr];
> +
> + pr_debug("Exceeds line range: nr_lines = %d, a_nr = %d\n",
> + info->nr_lines, a_nr);
> +
> + return NULL;
> +}
> +
> +void srclist__dump(struct srclist *slist)
> +{
> + struct src_node *node;
> + struct src_info *info;
> + int i;
> +
> + srclist__for_each_entry(node, slist) {
> + info = &node->info;
> +
> + pr_debug("%s (after -> before) lines mapping:\n",
> + info->rel_path);
> +
> + for (i = 0; i < info->nr_lines; i++) {
> + pr_debug("%d -> %d\n",
> + info->lines[i].a_nr,
> + info->lines[i].b_nr);
> + }
> + }
> +}
> diff --git a/tools/perf/util/srclist.h b/tools/perf/util/srclist.h
> new file mode 100644
> index 000000000000..f25b0de91a13
> --- /dev/null
> +++ b/tools/perf/util/srclist.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __PERF_SRCLIST_H
> +#define __PERF_SRCLIST_H
> +
> +#include <linux/types.h>
> +#include <linux/rbtree.h>
> +#include "rblist.h"
> +
> +struct line_pair {
> + int a_nr; /* line nr in after.c */
> + int b_nr; /* line nr in before.c */
> +};
> +
> +struct src_node;
> +
> +struct src_info {
> + char *rel_path; /* relative path */
> + struct line_pair *lines;
> + int nr_max;
> + int nr_lines;
> + int nr_lines_before;
> + int nr_lines_after;
> +};
> +
> +struct src_node {
> + struct rb_node rb_node;
> + struct src_info info;
> +};
> +
> +struct srclist {
> + struct rblist rblist;
> + const char *before_dir;
> + const char *after_dir;
> +};
> +
> +struct srclist *srclist__new(const char *before_dir, const char *after_dir);
> +void srclist__delete(struct srclist *slist);
> +
> +struct src_node *srclist__find(struct srclist *slist, char *rel_path,
> + bool create);
> +
> +struct line_pair *srclist__line_pair(struct src_node *node, int a_nr);
> +void srclist__dump(struct srclist *slist);
> +
> +static inline struct src_node *srclist__first(struct srclist *slist)
> +{
> + struct rb_node *rn = rb_first_cached(&slist->rblist.entries);
> +
> + return rn ? rb_entry(rn, struct src_node, rb_node) : NULL;
> +}
> +
> +static inline struct src_node *srclist__next(struct src_node *sn)
> +{
> + struct rb_node *rn;
> +
> + if (!sn)
> + return NULL;
> + rn = rb_next(&sn->rb_node);
> + return rn ? rb_entry(rn, struct src_node, rb_node) : NULL;
> +}
> +
> +#define srclist__for_each_entry(pos, slist) \
> + for (pos = srclist__first(slist); pos; pos = srclist__next(pos))
> +
> +#endif /* __PERF_SRCLIST_H */
> --
> 2.17.1
>

--

- Arnaldo

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