[PATCH] 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.

Also fix an error in the DWARF line table state machine where addresses
are incorrectly offset by -0x40 (GEN_ELF_TEXT_OFFSET). This can be seen
with `objdump -S` on the ELF files after perf inject.

Signed-off-by: Nick Gasson <nick.gasson@xxxxxxx>
---
 tools/perf/jvmti/libjvmti.c    | 73 +++++++++++++---------------------
 tools/perf/util/genelf_debug.c |  4 +-
 2 files changed, 30 insertions(+), 47 deletions(-)

diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
index a9a056d68416..398e4ba6498d 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 +107,12 @@ 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);
+				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++;
 			}
 		}
 	}
diff --git a/tools/perf/util/genelf_debug.c b/tools/perf/util/genelf_debug.c
index 30e9f618f6cd..dd40683bd4c0 100644
--- a/tools/perf/util/genelf_debug.c
+++ b/tools/perf/util/genelf_debug.c
@@ -342,7 +342,7 @@ static void emit_lineno_info(struct buffer_ext *be,
 	 */
 
 	/* start state of the state machine we take care of */
-	unsigned long last_vma = code_addr;
+	unsigned long last_vma = 0;
 	char const  *cur_filename = NULL;
 	unsigned long cur_file_idx = 0;
 	int last_line = 1;
@@ -473,7 +473,7 @@ jit_process_debug_info(uint64_t code_addr,
 		ent = debug_entry_next(ent);
 	}
 	add_compilation_unit(di, buffer_ext_size(dl));
-	add_debug_line(dl, debug, nr_debug_entries, 0);
+	add_debug_line(dl, debug, nr_debug_entries, GEN_ELF_TEXT_OFFSET);
 	add_debug_abbrev(da);
 	if (0) buffer_ext_dump(da, "abbrev");
 
-- 
2.26.2