Date:   Tue, 28 Apr 2020 16:27:47 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v3 1/7] perf util: Create source line mapping table

Hi Jiri,

On 4/27/2020 6:11 PM, Jiri Olsa wrote:
> On Mon, Apr 20, 2020 at 09:04:45AM +0800, Jin Yao wrote:
>> 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
> 
> hi,
> I'm getting compile error with this patch:
> 
> 	[jolsa@...va perf]$ make JOBS=1
> 	  BUILD:   Doing 'make -j1' parallel build
> 	  CC       util/srclist.o
> 	util/srclist.c: In function ‘srclist__node_new’:
> 	util/srclist.c:388:35: error: ‘%s’ directive output may be truncated writing up to 4095 bytes into a region of size 4091 [-Werror=format-truncation=]
> 	  388 |  snprintf(cmd, sizeof(cmd), "diff %s %s",
> 	      |                                   ^~
> 	......

There is no error in my compilation.

But anyway, is it ok to use snprintf(cmd, PATH_MAX, "diff %s %s", b_path, 
a_path) instead?

Thanks
Jin Yao

> 	  456 |  ret = init_src_info(b_path, a_path, rel_path, &node->info);
> 	      |                      ~~~~~~
> 	In file included from /usr/include/stdio.h:867,
> 			 from util/srclist.c:8:
> 	/usr/include/bits/stdio2.h:67:10: note: ‘__builtin___snprintf_chk’ output between 7 and 8197 bytes into a destination of size 4096
> 	   67 |   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
> 	      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 	   68 |        __bos (__s), __fmt, __va_arg_pack ());
> 	      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 	cc1: all warnings being treated as errors
> 	mv: cannot stat 'util/.srclist.o.tmp': No such file or directory
> 	make[4]: *** [/home/jolsa/kernel/linux-perf/tools/build/Makefile.build:97: util/srclist.o] Error 1
> 	make[3]: *** [/home/jolsa/kernel/linux-perf/tools/build/Makefile.build:139: util] Error 2
> 	make[2]: *** [Makefile.perf:617: perf-in.o] Error 2
> 	make[1]: *** [Makefile.perf:225: sub-make] Error 2
> 	make: *** [Makefile:70: all] Error 2
> 
> thanks,
> jirka
> 
> 
>>
>> 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.
>>
>>   v2:
>>   ---
>>   Refine the code
>>   1. calloc -> zalloc
>>   2. Functions operating on a 'struct line_pair' have the
>>      line_pair__ prefix.
>>   3. Check get_range() return value.
>>   4. Use fgets to replace fgetc for getting the number of lines.
>>   5. Use path__join to generate the full path.
>>   6. Keep the buffer after calling getline.
>>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>>   tools/perf/util/Build     |   1 +
>>   tools/perf/util/srclist.c | 555 ++++++++++++++++++++++++++++++++++++++
>>   tools/perf/util/srclist.h |  65 +++++
>>   3 files changed, 621 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..8060e4855d11
>> --- /dev/null
>> +++ b/tools/perf/util/srclist.c
>> @@ -0,0 +1,555 @@
>> +// 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"
>> +#include "path.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;
>> +	}
>> +
>> +	path__join(full_path, size, dir, rel_path);
>> +}
>> +
>> +static int path__number_of_lines(char *path)
>> +{
>> +	FILE *fp;
>> +	char buf[4096], *p, last = 0;
>> +	int num = 0;
>> +
>> +	fp = fopen(path, "r");
>> +	if (!fp) {
>> +		pr_debug("Failed to open file %s\n", path);
>> +		return -1;
>> +	}
>> +
>> +	while (!feof(fp)) {
>> +		p = fgets(buf, sizeof(buf), fp);
>> +		if (!p)
>> +			break;
>> +
>> +		last = p[strlen(p) - 1];
>> +		if (last == '\n')
>> +			num++;
>> +	}
>> +
>> +	fclose(fp);
>> +
>> +	if (last != '\n' && last != 0)
>> +		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;
>> +		if (get_range(str, b_start, b_end) != 0)
>> +			return false;
>> +
>> +		if (get_range(&str[idx + 1], a_start, a_end) != 0)
>> +			return false;
>> +
>> +		return true;
>> +	}
>> +
>> +	return false;
>> +}
>> +
>> +static int line_pair__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 line 5 ~ line 6 of file1 are not same as line 4 of file2
>> +	 * because line 5 ~ line 6 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 line_pair__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 line 8 at file1 is not same as line 7 at file2
>> +	 * because a new line (line 7) 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 line_pair__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 line_pair__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)
>> +{
>> +	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:
>> +		line_pair__del_lines(lines, b_start, b_end, a_start, a_end,
>> +				     nr_lines, b_adjust);
>> +		break;
>> +
>> +	case DIFF_LINE_ADD:
>> +		line_pair__add_lines(lines, b_start, b_end, a_start, a_end,
>> +				     nr_lines, b_adjust);
>> +		break;
>> +
>> +	case DIFF_LINE_CHANGE:
>> +		line_pair__change_lines(lines, b_start, b_end, a_start,
>> +					a_end, nr_lines, b_adjust);
>> +		break;
>> +
>> +	default:
>> +		break;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static void line_pair__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 *fp, struct line_pair *lines,
>> +			       int *nr_lines, int a_num)
>> +{
>> +	char *str = NULL, *p;
>> +	size_t len = 0;
>> +	int opr, b_start, b_end, a_start, a_end, b_adjust = 0;
>> +
>> +	*nr_lines = 1;  /* First line is reserved */
>> +
>> +	while (getline(&str, &len, fp) > 0) {
>> +		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;
>> +		}
>> +
>> +		line_pair__update_lines(lines, opr, b_start, b_end, a_start,
>> +					a_end, nr_lines, &b_adjust);
>> +	}
>> +
>> +	line_pair__update_remaining(lines, a_num, nr_lines, b_adjust);
>> +
>> +	free(str);
>> +	return 0;
>> +}
>> +
>> +static int src_info__create_line_mapping(struct src_info *info, char *b_path,
>> +					 char *a_path)
>> +{
>> +	char cmd[PATH_MAX];
>> +	FILE *fp = NULL;
>> +	int ret = -1;
>> +
>> +	info->nr_lines_before = path__number_of_lines(b_path);
>> +	if (info->nr_lines_before == -1)
>> +		goto out;
>> +
>> +	info->nr_lines_after = path__number_of_lines(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);
>> +
>> +	fp = popen(cmd, "r");
>> +	if (!fp) {
>> +		pr_err("Failed to execute '%s'\n", cmd);
>> +		goto out;
>> +	}
>> +
>> +	ret = build_mapping_table(fp, info->lines, &info->nr_lines,
>> +				  info->nr_lines_after);
>> +
>> +out:
>> +	if (fp)
>> +		fclose(fp);
>> +
>> +	return ret;
>> +}
>> +
>> +static void free_src_info(struct src_info *info)
>> +{
>> +	zfree(&info->rel_path);
>> +	zfree(&info->lines);
>> +}
>> +
>> +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 = src_info__create_line_mapping(info, b_path, a_path);
>> +	if (ret)
>> +		free_src_info(info);
>> +
>> +	return ret;
>> +}
>> +
>> +static void free_src_node(struct src_node *node)
>> +{
>> +	if (!node)
>> +		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 = zalloc(sizeof(*node));
>> +	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 = zalloc(sizeof(*slist));
>> +
>> +	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);
>> +}
>> +
>> +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
>>
> 

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