veristat: add ability to sort by stat's absolute value

Add ability to sort results by absolute values of specified stats. This
is especially useful to find biggest deviations in comparison mode. When
comparing verifier change effect against a large base of BPF object
files, it's necessary to see big changes both in positive and negative
directions, as both might be a signal for regressions or bugs.

The syntax is natural, e.g., adding `-s '|insns_diff|'^` will instruct
veristat to sort by absolute value of instructions difference in
ascending order.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231108051430.1830950-1-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/veristat.c

@@ -18,6 +18,7 @@
 #include <libelf.h>
 #include <gelf.h>
 #include <float.h>
+#include <math.h>
 
 #ifndef ARRAY_SIZE
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
@@ -99,6 +100,7 @@ struct stat_specs {
 	enum stat_id ids[ALL_STATS_CNT];
 	enum stat_variant variants[ALL_STATS_CNT];
 	bool asc[ALL_STATS_CNT];
+	bool abs[ALL_STATS_CNT];
 	int lens[ALL_STATS_CNT * 3]; /* 3x for comparison mode */
 };
 
@@ -133,6 +135,7 @@ struct filter {
 	int stat_id;
 	enum stat_variant stat_var;
 	long value;
+	bool abs;
 };
 
 static struct env {
@@ -455,7 +458,8 @@ static struct {
 	{ OP_EQ, "=" },
 };
 
-static bool parse_stat_id_var(const char *name, size_t len, int *id, enum stat_variant *var);
+static bool parse_stat_id_var(const char *name, size_t len, int *id,
+			      enum stat_variant *var, bool *is_abs);
 
 static int append_filter(struct filter **filters, int *cnt, const char *str)
 {
@@ -488,13 +492,14 @@ static int append_filter(struct filter **filters, int *cnt, const char *str)
 		long val;
 		const char *end = str;
 		const char *op_str;
+		bool is_abs;
 
 		op_str = operators[i].op_str;
 		p = strstr(str, op_str);
 		if (!p)
 			continue;
 
-		if (!parse_stat_id_var(str, p - str, &id, &var)) {
+		if (!parse_stat_id_var(str, p - str, &id, &var, &is_abs)) {
 			fprintf(stderr, "Unrecognized stat name in '%s'!\n", str);
 			return -EINVAL;
 		}
@@ -533,6 +538,7 @@ static int append_filter(struct filter **filters, int *cnt, const char *str)
 		f->stat_id = id;
 		f->stat_var = var;
 		f->op = operators[i].op_kind;
+		f->abs = true;
 		f->value = val;
 
 		*cnt += 1;
@@ -657,7 +663,8 @@ static struct stat_def {
 	[MARK_READ_MAX_LEN] = { "Max mark read length", {"max_mark_read_len", "mark_read"}, },
 };
 
-static bool parse_stat_id_var(const char *name, size_t len, int *id, enum stat_variant *var)
+static bool parse_stat_id_var(const char *name, size_t len, int *id,
+			      enum stat_variant *var, bool *is_abs)
 {
 	static const char *var_sfxs[] = {
 		[VARIANT_A] = "_a",
@@ -667,6 +674,14 @@ static bool parse_stat_id_var(const char *name, size_t len, int *id, enum stat_v
 	};
 	int i, j, k;
 
+	/* |<stat>| means we take absolute value of given stat */
+	*is_abs = false;
+	if (len > 2 && name[0] == '|' && name[len - 1] == '|') {
+		*is_abs = true;
+		name += 1;
+		len -= 2;
+	}
+
 	for (i = 0; i < ARRAY_SIZE(stat_defs); i++) {
 		struct stat_def *def = &stat_defs[i];
 		size_t alias_len, sfx_len;
@@ -722,7 +737,7 @@ static bool is_desc_sym(char c)
 static int parse_stat(const char *stat_name, struct stat_specs *specs)
 {
 	int id;
-	bool has_order = false, is_asc = false;
+	bool has_order = false, is_asc = false, is_abs = false;
 	size_t len = strlen(stat_name);
 	enum stat_variant var;
 
@@ -737,7 +752,7 @@ static int parse_stat(const char *stat_name, struct stat_specs *specs)
 		len -= 1;
 	}
 
-	if (!parse_stat_id_var(stat_name, len, &id, &var)) {
+	if (!parse_stat_id_var(stat_name, len, &id, &var, &is_abs)) {
 		fprintf(stderr, "Unrecognized stat name '%s'\n", stat_name);
 		return -ESRCH;
 	}
@@ -745,6 +760,7 @@ static int parse_stat(const char *stat_name, struct stat_specs *specs)
 	specs->ids[specs->spec_cnt] = id;
 	specs->variants[specs->spec_cnt] = var;
 	specs->asc[specs->spec_cnt] = has_order ? is_asc : stat_defs[id].asc_by_default;
+	specs->abs[specs->spec_cnt] = is_abs;
 	specs->spec_cnt++;
 
 	return 0;
@@ -1103,7 +1119,7 @@ static int process_obj(const char *filename)
 }
 
 static int cmp_stat(const struct verif_stats *s1, const struct verif_stats *s2,
-		    enum stat_id id, bool asc)
+		    enum stat_id id, bool asc, bool abs)
 {
 	int cmp = 0;
 
@@ -1124,6 +1140,11 @@ static int cmp_stat(const struct verif_stats *s1, const struct verif_stats *s2,
 		long v1 = s1->stats[id];
 		long v2 = s2->stats[id];
 
+		if (abs) {
+			v1 = v1 < 0 ? -v1 : v1;
+			v2 = v2 < 0 ? -v2 : v2;
+		}
+
 		if (v1 != v2)
 			cmp = v1 < v2 ? -1 : 1;
 		break;
@@ -1142,7 +1163,8 @@ static int cmp_prog_stats(const void *v1, const void *v2)
 	int i, cmp;
 
 	for (i = 0; i < env.sort_spec.spec_cnt; i++) {
-		cmp = cmp_stat(s1, s2, env.sort_spec.ids[i], env.sort_spec.asc[i]);
+		cmp = cmp_stat(s1, s2, env.sort_spec.ids[i],
+			       env.sort_spec.asc[i], env.sort_spec.abs[i]);
 		if (cmp != 0)
 			return cmp;
 	}
@@ -1211,7 +1233,8 @@ static void fetch_join_stat_value(const struct verif_stats_join *s,
 
 static int cmp_join_stat(const struct verif_stats_join *s1,
 			 const struct verif_stats_join *s2,
-			 enum stat_id id, enum stat_variant var, bool asc)
+			 enum stat_id id, enum stat_variant var,
+			 bool asc, bool abs)
 {
 	const char *str1 = NULL, *str2 = NULL;
 	double v1, v2;
@@ -1220,6 +1243,11 @@ static int cmp_join_stat(const struct verif_stats_join *s1,
 	fetch_join_stat_value(s1, id, var, &str1, &v1);
 	fetch_join_stat_value(s2, id, var, &str2, &v2);
 
+	if (abs) {
+		v1 = fabs(v1);
+		v2 = fabs(v2);
+	}
+
 	if (str1)
 		cmp = strcmp(str1, str2);
 	else if (v1 != v2)
@@ -1237,7 +1265,8 @@ static int cmp_join_stats(const void *v1, const void *v2)
 		cmp = cmp_join_stat(s1, s2,
 				    env.sort_spec.ids[i],
 				    env.sort_spec.variants[i],
-				    env.sort_spec.asc[i]);
+				    env.sort_spec.asc[i],
+				    env.sort_spec.abs[i]);
 		if (cmp != 0)
 			return cmp;
 	}
@@ -1720,6 +1749,9 @@ static bool is_join_stat_filter_matched(struct filter *f, const struct verif_sta
 
 	fetch_join_stat_value(stats, f->stat_id, f->stat_var, &str, &value);
 
+	if (f->abs)
+		value = fabs(value);
+
 	switch (f->op) {
 	case OP_EQ: return value > f->value - eps && value < f->value + eps;
 	case OP_NEQ: return value < f->value - eps || value > f->value + eps;
@@ -1766,7 +1798,7 @@ static int handle_comparison_mode(void)
 	struct stat_specs base_specs = {}, comp_specs = {};
 	struct stat_specs tmp_sort_spec;
 	enum resfmt cur_fmt;
-	int err, i, j, last_idx;
+	int err, i, j, last_idx, cnt;
 
 	if (env.filename_cnt != 2) {
 		fprintf(stderr, "Comparison mode expects exactly two input CSV files!\n\n");
@@ -1879,7 +1911,7 @@ static int handle_comparison_mode(void)
 		env.join_stat_cnt += 1;
 	}
 
-	/* now sort joined results accorsing to sort spec */
+	/* now sort joined results according to sort spec */
 	qsort(env.join_stats, env.join_stat_cnt, sizeof(*env.join_stats), cmp_join_stats);
 
 	/* for human-readable table output we need to do extra pass to
@@ -1896,16 +1928,22 @@ static int handle_comparison_mode(void)
 	output_comp_headers(cur_fmt);
 
 	last_idx = -1;
+	cnt = 0;
 	for (i = 0; i < env.join_stat_cnt; i++) {
 		const struct verif_stats_join *join = &env.join_stats[i];
 
 		if (!should_output_join_stats(join))
 			continue;
 
+		if (env.top_n && cnt >= env.top_n)
+			break;
+
 		if (cur_fmt == RESFMT_TABLE_CALCLEN)
 			last_idx = i;
 
 		output_comp_stats(join, cur_fmt, i == last_idx);
+
+		cnt++;
 	}
 
 	if (cur_fmt == RESFMT_TABLE_CALCLEN) {
@@ -1920,6 +1958,9 @@ static bool is_stat_filter_matched(struct filter *f, const struct verif_stats *s
 {
 	long value = stats->stats[f->stat_id];
 
+	if (f->abs)
+		value = value < 0 ? -value : value;
+
 	switch (f->op) {
 	case OP_EQ: return value == f->value;
 	case OP_NEQ: return value != f->value;
@@ -1964,7 +2005,7 @@ static bool should_output_stats(const struct verif_stats *stats)
 static void output_prog_stats(void)
 {
 	const struct verif_stats *stats;
-	int i, last_stat_idx = 0;
+	int i, last_stat_idx = 0, cnt = 0;
 
 	if (env.out_fmt == RESFMT_TABLE) {
 		/* calculate column widths */
@@ -1984,7 +2025,10 @@ static void output_prog_stats(void)
 		stats = &env.prog_stats[i];
 		if (!should_output_stats(stats))
 			continue;
+		if (env.top_n && cnt >= env.top_n)
+			break;
 		output_stats(stats, env.out_fmt, i == last_stat_idx);
+		cnt++;
 	}
 }