[PATCH v2] perf jvmti: Remove redundant jitdump line table entries

[Nick Gasson]

For each PC/BCI pair in the JVMTI compiler inlining record table, the
jitdump plugin emits debug line table entries for every source line in
the method preceding that BCI. Instead only emit one source line per
PC/BCI pair. Reported by Ian Rogers. This reduces the .dump size for
SPECjbb from ~230MB to ~40MB.

Signed-off-by: Nick Gasson <nick.gasson@xxxxxxx>
---
Changes in v2:
- Split the unrelated DWARF debug fix into a separate patch
- Added a comment about the use of c->methods

 tools/perf/jvmti/libjvmti.c | 78 ++++++++++++++++---------------------
 1 file changed, 33 insertions(+), 45 deletions(-)

diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
index c5d30834a64c..fcca275e5bf9 100644
--- a/tools/perf/jvmti/libjvmti.c
+++ b/tools/perf/jvmti/libjvmti.c
@@ -32,38 +32,41 @@ static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
 
 #ifdef HAVE_JVMTI_CMLR
 static jvmtiError
-do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
-		    jvmti_line_info_t *tab, jint *nr)
+do_get_line_number(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
+		   jvmti_line_info_t *tab)
 {
-	jint i, lines = 0;
-	jint nr_lines = 0;
+	jint i, nr_lines = 0;
 	jvmtiLineNumberEntry *loc_tab = NULL;
 	jvmtiError ret;
+	jint src_line = -1;
 
 	ret = (*jvmti)->GetLineNumberTable(jvmti, m, &nr_lines, &loc_tab);
 	if (ret == JVMTI_ERROR_ABSENT_INFORMATION || ret == JVMTI_ERROR_NATIVE_METHOD) {
 		/* No debug information for this method */
-		*nr = 0;
-		return JVMTI_ERROR_NONE;
+		return ret;
 	} else if (ret != JVMTI_ERROR_NONE) {
 		print_error(jvmti, "GetLineNumberTable", ret);
 		return ret;
 	}
 
-	for (i = 0; i < nr_lines; i++) {
-		if (loc_tab[i].start_location < bci) {
-			tab[lines].pc = (unsigned long)pc;
-			tab[lines].line_number = loc_tab[i].line_number;
-			tab[lines].discrim = 0; /* not yet used */
-			tab[lines].methodID = m;
-			lines++;
-		} else {
-			break;
-		}
+	for (i = 0; i < nr_lines && loc_tab[i].start_location <= bci; i++) {
+		src_line = i;
+	}
+
+	if (src_line != -1) {
+		tab->pc = (unsigned long)pc;
+		tab->line_number = loc_tab[src_line].line_number;
+		tab->discrim = 0; /* not yet used */
+		tab->methodID = m;
+
+		ret = JVMTI_ERROR_NONE;
+	} else {
+		ret = JVMTI_ERROR_ABSENT_INFORMATION;
 	}
+
 	(*jvmti)->Deallocate(jvmti, (unsigned char *)loc_tab);
-	*nr = lines;
-	return JVMTI_ERROR_NONE;
+
+	return ret;
 }
 
 static jvmtiError
@@ -71,9 +74,8 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **
 {
 	const jvmtiCompiledMethodLoadRecordHeader *hdr;
 	jvmtiCompiledMethodLoadInlineRecord *rec;
-	jvmtiLineNumberEntry *lne = NULL;
 	PCStackInfo *c;
-	jint nr, ret;
+	jint ret;
 	int nr_total = 0;
 	int i, lines_total = 0;
 
@@ -86,24 +88,7 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **
 	for (hdr = compile_info; hdr != NULL; hdr = hdr->next) {
 		if (hdr->kind == JVMTI_CMLR_INLINE_INFO) {
 			rec = (jvmtiCompiledMethodLoadInlineRecord *)hdr;
-			for (i = 0; i < rec->numpcs; i++) {
-				c = rec->pcinfo + i;
-				nr = 0;
-				/*
-				 * unfortunately, need a tab to get the number of lines!
-				 */
-				ret = (*jvmti)->GetLineNumberTable(jvmti, c->methods[0], &nr, &lne);
-				if (ret == JVMTI_ERROR_NONE) {
-					/* free what was allocated for nothing */
-					(*jvmti)->Deallocate(jvmti, (unsigned char *)lne);
-					nr_total += (int)nr;
-				} else if (ret == JVMTI_ERROR_ABSENT_INFORMATION ||
-					   ret == JVMTI_ERROR_NATIVE_METHOD) {
-					/* No debug information for this method */
-				} else {
-					print_error(jvmti, "GetLineNumberTable", ret);
-				}
-			}
+			nr_total += rec->numpcs;
 		}
 	}
 
@@ -122,14 +107,17 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **
 			rec = (jvmtiCompiledMethodLoadInlineRecord *)hdr;
 			for (i = 0; i < rec->numpcs; i++) {
 				c = rec->pcinfo + i;
-				nr = 0;
-				ret = do_get_line_numbers(jvmti, c->pc,
-							  c->methods[0],
-							  c->bcis[0],
-							  *tab + lines_total,
-							  &nr);
+                                /*
+                                 * c->methods is the stack of inlined method calls
+                                 * at c->pc. [0] is the leaf method. Caller frames
+                                 * are ignored at the moment.
+                                 */
+				ret = do_get_line_number(jvmti, c->pc,
+							 c->methods[0],
+							 c->bcis[0],
+							 *tab + lines_total);
 				if (ret == JVMTI_ERROR_NONE)
-					lines_total += nr;
+					lines_total++;
 			}
 		}
 	}
-- 
2.26.2