selftests/bpf: handle missing records in comparison mode better in veristat

When comparing two datasets, if either side is missing corresponding
record with the same file and prog name, currently veristat emits
misleading zeros/failures, and even tried to calculate a difference,
even though there is no data to compare against.

This patch improves internal logic of handling such situations. Now
we'll emit "N/A" in places where data is missing and comparison is
non-sensical.

As an example, in an artificially truncated and mismatched Cilium
results, the output looks like below:

  $ ./veristat -e file,prog,verdict,insns -C ~/base.csv ~/comp.csv
  File                Program                         Verdict (A)  Verdict (B)  Verdict (DIFF)  Insns (A)  Insns (B)  Insns   (DIFF)
  ------------------  ------------------------------  -----------  -----------  --------------  ---------  ---------  --------------
  bpf_alignchecker.o  __send_drop_notify              success      N/A          N/A                    53        N/A             N/A
  bpf_alignchecker.o  tail_icmp6_handle_ns            failure      failure      MATCH                  33         33     +0 (+0.00%)
  bpf_alignchecker.o  tail_icmp6_send_echo_reply      N/A          failure      N/A                   N/A         74             N/A
  bpf_host.o          __send_drop_notify              success      N/A          N/A                    53        N/A             N/A
  bpf_host.o          cil_from_host                   success      N/A          N/A                   762        N/A             N/A
  bpf_xdp.o           __send_drop_notify              success      success      MATCH                 151        151     +0 (+0.00%)
  bpf_xdp.o           cil_xdp_entry                   success      success      MATCH                 423        423     +0 (+0.00%)
  bpf_xdp.o           tail_handle_nat_fwd_ipv4        success      success      MATCH               21547      20920   -627 (-2.91%)
  bpf_xdp.o           tail_handle_nat_fwd_ipv6        success      success      MATCH               16974      17039    +65 (+0.38%)
  bpf_xdp.o           tail_lb_ipv4                    success      success      MATCH               71736      73430  +1694 (+2.36%)
  bpf_xdp.o           tail_lb_ipv6                    N/A          success      N/A                   N/A     151895             N/A
  bpf_xdp.o           tail_nodeport_ipv4_dsr          N/A          success      N/A                   N/A       1162             N/A
  bpf_xdp.o           tail_nodeport_ipv6_dsr          N/A          success      N/A                   N/A       1206             N/A
  bpf_xdp.o           tail_nodeport_nat_egress_ipv4   N/A          success      N/A                   N/A      15619             N/A
  bpf_xdp.o           tail_nodeport_nat_ingress_ipv4  success      success      MATCH                7658       7713    +55 (+0.72%)
  bpf_xdp.o           tail_nodeport_nat_ingress_ipv6  success      success      MATCH                6405       6397     -8 (-0.12%)
  bpf_xdp.o           tail_nodeport_nat_ipv6_egress   failure      failure      MATCH                 752        752     +0 (+0.00%)
  bpf_xdp.o           tail_rev_nodeport_lb4           success      success      MATCH                7126       6934   -192 (-2.69%)
  bpf_xdp.o           tail_rev_nodeport_lb6           success      success      MATCH               17954      17905    -49 (-0.27%)
  ------------------  ------------------------------  -----------  -----------  --------------  ---------  ---------  --------------

Internally veristat now separates joining two datasets and remembering the
join, and actually emitting a comparison view. This will come handy when we add
support for filtering and custom ordering in comparison mode.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221103055304.2904589-9-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/veristat.c

@@ -41,6 +41,15 @@ struct verif_stats {
 	long stats[NUM_STATS_CNT];
 };
 
+/* joined comparison mode stats */
+struct verif_stats_join {
+	char *file_name;
+	char *prog_name;
+
+	const struct verif_stats *stats_a;
+	const struct verif_stats *stats_b;
+};
+
 struct stat_specs {
 	int spec_cnt;
 	enum stat_id ids[ALL_STATS_CNT];
@@ -97,6 +106,9 @@ static struct env {
 	struct verif_stats *baseline_stats;
 	int baseline_stat_cnt;
 
+	struct verif_stats_join *join_stats;
+	int join_stat_cnt;
+
 	struct stat_specs output_spec;
 	struct stat_specs sort_spec;
 
@@ -518,6 +530,15 @@ static const struct stat_specs default_sort_spec = {
 	.asc = { true, true, },
 };
 
+/* sorting for comparison mode to join two data sets */
+static const struct stat_specs join_sort_spec = {
+	.spec_cnt = 2,
+	.ids = {
+		FILE_NAME, PROG_NAME,
+	},
+	.asc = { true, true, },
+};
+
 static struct stat_def {
 	const char *header;
 	const char *names[4];
@@ -934,13 +955,16 @@ static void prepare_value(const struct verif_stats *s, enum stat_id id,
 {
 	switch (id) {
 	case FILE_NAME:
-		*str = s->file_name;
+		*str = s ? s->file_name : "N/A";
 		break;
 	case PROG_NAME:
-		*str = s->prog_name;
+		*str = s ? s->prog_name : "N/A";
 		break;
 	case VERDICT:
-		*str = s->stats[VERDICT] ? "success" : "failure";
+		if (!s)
+			*str = "N/A";
+		else
+			*str = s->stats[VERDICT] ? "success" : "failure";
 		break;
 	case DURATION:
 	case TOTAL_INSNS:
@@ -948,7 +972,7 @@ static void prepare_value(const struct verif_stats *s, enum stat_id id,
 	case PEAK_STATES:
 	case MAX_STATES_PER_INSN:
 	case MARK_READ_MAX_LEN:
-		*val = s->stats[id];
+		*val = s ? s->stats[id] : 0;
 		break;
 	default:
 		fprintf(stderr, "Unrecognized stat #%d\n", id);
@@ -1223,9 +1247,11 @@ static void output_comp_headers(enum resfmt fmt)
 		output_comp_header_underlines();
 }
 
-static void output_comp_stats(const struct verif_stats *base, const struct verif_stats *comp,
+static void output_comp_stats(const struct verif_stats_join *join_stats,
 			      enum resfmt fmt, bool last)
 {
+	const struct verif_stats *base = join_stats->stats_a;
+	const struct verif_stats *comp = join_stats->stats_b;
 	char base_buf[1024] = {}, comp_buf[1024] = {}, diff_buf[1024] = {};
 	int i;
 
@@ -1243,33 +1269,45 @@ static void output_comp_stats(const struct verif_stats *base, const struct verif
 		/* normalize all the outputs to be in string buffers for simplicity */
 		if (is_key_stat(id)) {
 			/* key stats (file and program name) are always strings */
-			if (base != &fallback_stats)
+			if (base)
 				snprintf(base_buf, sizeof(base_buf), "%s", base_str);
 			else
 				snprintf(base_buf, sizeof(base_buf), "%s", comp_str);
 		} else if (base_str) {
 			snprintf(base_buf, sizeof(base_buf), "%s", base_str);
 			snprintf(comp_buf, sizeof(comp_buf), "%s", comp_str);
-			if (strcmp(base_str, comp_str) == 0)
+			if (!base || !comp)
+				snprintf(diff_buf, sizeof(diff_buf), "%s", "N/A");
+			else if (strcmp(base_str, comp_str) == 0)
 				snprintf(diff_buf, sizeof(diff_buf), "%s", "MATCH");
 			else
 				snprintf(diff_buf, sizeof(diff_buf), "%s", "MISMATCH");
 		} else {
 			double p = 0.0;
 
-			snprintf(base_buf, sizeof(base_buf), "%ld", base_val);
-			snprintf(comp_buf, sizeof(comp_buf), "%ld", comp_val);
+			if (base)
+				snprintf(base_buf, sizeof(base_buf), "%ld", base_val);
+			else
+				snprintf(base_buf, sizeof(base_buf), "%s", "N/A");
+			if (comp)
+				snprintf(comp_buf, sizeof(comp_buf), "%ld", comp_val);
+			else
+				snprintf(comp_buf, sizeof(comp_buf), "%s", "N/A");
 
 			diff_val = comp_val - base_val;
-			if (base == &fallback_stats || comp == &fallback_stats || base_val == 0) {
-				if (comp_val == base_val)
-					p = 0.0; /* avoid +0 (+100%) case */
-				else
-					p = comp_val < base_val ? -100.0 : 100.0;
+			if (!base || !comp) {
+				snprintf(diff_buf, sizeof(diff_buf), "%s", "N/A");
 			} else {
-				 p = diff_val * 100.0 / base_val;
+				if (base_val == 0) {
+					if (comp_val == base_val)
+						p = 0.0; /* avoid +0 (+100%) case */
+					else
+						p = comp_val < base_val ? -100.0 : 100.0;
+				} else {
+					 p = diff_val * 100.0 / base_val;
+				}
+				snprintf(diff_buf, sizeof(diff_buf), "%+ld (%+.2lf%%)", diff_val, p);
 			}
-			snprintf(diff_buf, sizeof(diff_buf), "%+ld (%+.2lf%%)", diff_val, p);
 		}
 
 		switch (fmt) {
@@ -1328,6 +1366,7 @@ static int cmp_stats_key(const struct verif_stats *base, const struct verif_stat
 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;
 
@@ -1370,31 +1409,26 @@ static int handle_comparison_mode(void)
 		}
 	}
 
+	/* Replace user-specified sorting spec with file+prog sorting rule to
+	 * be able to join two datasets correctly. Once we are done, we will
+	 * restore the original sort spec.
+	 */
+	tmp_sort_spec = env.sort_spec;
+	env.sort_spec = join_sort_spec;
 	qsort(env.prog_stats, env.prog_stat_cnt, sizeof(*env.prog_stats), cmp_prog_stats);
 	qsort(env.baseline_stats, env.baseline_stat_cnt, sizeof(*env.baseline_stats), cmp_prog_stats);
+	env.sort_spec = tmp_sort_spec;
 
-	/* for human-readable table output we need to do extra pass to
-	 * calculate column widths, so we substitute current output format
-	 * with RESFMT_TABLE_CALCLEN and later revert it back to RESFMT_TABLE
-	 * and do everything again.
-	 */
-	if (env.out_fmt == RESFMT_TABLE)
-		cur_fmt = RESFMT_TABLE_CALCLEN;
-	else
-		cur_fmt = env.out_fmt;
-
-one_more_time:
-	output_comp_headers(cur_fmt);
-
-	/* If baseline and comparison datasets have different subset of rows
-	 * (we match by 'object + prog' as a unique key) then assume
-	 * empty/missing/zero value for rows that are missing in the opposite
-	 * data set
+	/* Join two datasets together. If baseline and comparison datasets
+	 * have different subset of rows (we match by 'object + prog' as
+	 * a unique key) then assume empty/missing/zero value for rows that
+	 * are missing in the opposite data set.
 	 */
 	i = j = 0;
 	while (i < env.baseline_stat_cnt || j < env.prog_stat_cnt) {
-		bool last = (i == env.baseline_stat_cnt - 1) || (j == env.prog_stat_cnt - 1);
 		const struct verif_stats *base, *comp;
+		struct verif_stats_join *join;
+		void *tmp;
 		int r;
 
 		base = i < env.baseline_stat_cnt ? &env.baseline_stats[i] : &fallback_stats;
@@ -1411,18 +1445,56 @@ static int handle_comparison_mode(void)
 			return -EINVAL;
 		}
 
+		tmp = realloc(env.join_stats, (env.join_stat_cnt + 1) * sizeof(*env.join_stats));
+		if (!tmp)
+			return -ENOMEM;
+		env.join_stats = tmp;
+
+		join = &env.join_stats[env.join_stat_cnt];
+		memset(join, 0, sizeof(*join));
+
 		r = cmp_stats_key(base, comp);
 		if (r == 0) {
-			output_comp_stats(base, comp, cur_fmt, last);
+			join->file_name = base->file_name;
+			join->prog_name = base->prog_name;
+			join->stats_a = base;
+			join->stats_b = comp;
 			i++;
 			j++;
 		} else if (comp == &fallback_stats || r < 0) {
-			output_comp_stats(base, &fallback_stats, cur_fmt, last);
+			join->file_name = base->file_name;
+			join->prog_name = base->prog_name;
+			join->stats_a = base;
+			join->stats_b = NULL;
 			i++;
 		} else {
-			output_comp_stats(&fallback_stats, comp, cur_fmt, last);
+			join->file_name = comp->file_name;
+			join->prog_name = comp->prog_name;
+			join->stats_a = NULL;
+			join->stats_b = comp;
 			j++;
 		}
+		env.join_stat_cnt += 1;
+	}
+
+	/* for human-readable table output we need to do extra pass to
+	 * calculate column widths, so we substitute current output format
+	 * with RESFMT_TABLE_CALCLEN and later revert it back to RESFMT_TABLE
+	 * and do everything again.
+	 */
+	if (env.out_fmt == RESFMT_TABLE)
+		cur_fmt = RESFMT_TABLE_CALCLEN;
+	else
+		cur_fmt = env.out_fmt;
+
+one_more_time:
+	output_comp_headers(cur_fmt);
+
+	for (i = 0; i < env.join_stat_cnt; i++) {
+		const struct verif_stats_join *join = &env.join_stats[i];
+		bool last = i == env.join_stat_cnt - 1;
+
+		output_comp_stats(join, cur_fmt, last);
 	}
 
 	if (cur_fmt == RESFMT_TABLE_CALCLEN) {
@@ -1594,6 +1666,7 @@ int main(int argc, char **argv)
 
 	free_verif_stats(env.prog_stats, env.prog_stat_cnt);
 	free_verif_stats(env.baseline_stats, env.baseline_stat_cnt);
+	free(env.join_stats);
 	for (i = 0; i < env.filename_cnt; i++)
 		free(env.filenames[i]);
 	free(env.filenames);