[PATCH v2 1/2] scripts: ftrace - move the sort-processing in ftrace_init to compile time

[Yinan Liu]

When the kernel starts, the initialization of fTrace takes
up a portion of the time (approximately 6~8ms) to sort mcount
addresses. We can save this time by moving mcount-sorting to
compile time.

After communication with Patch V1, it is concluded that it is
more meaningful to sort mcount addresses in vmlinux during
compilation, which is not suitable for kernel module at present.
Patch V2 has adjusted some variable names and comments.

Signed-off-by: Yinan Liu <yinan@xxxxxxxxxxxxxxxxx>
---
 kernel/trace/ftrace.c   |   5 ++-
 scripts/link-vmlinux.sh |   6 +--
 scripts/sorttable.c     |   2 +
 scripts/sorttable.h     | 109 +++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 115 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 30bc880c3849..c776a2956237 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6406,8 +6406,9 @@ static int ftrace_process_locs(struct module *mod,
 	if (!count)
 		return 0;
 
-	sort(start, count, sizeof(*start),
-	     ftrace_cmp_ips, NULL);
+	if (mod)
+		sort(start, count, sizeof(*start),
+		     ftrace_cmp_ips, NULL);
 
 	start_pg = ftrace_allocate_pages(count);
 	if (!start_pg)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 5cdd9bc5c385..dd9955f45774 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -400,6 +400,9 @@ if [ -n "${CONFIG_DEBUG_INFO_BTF}" -a -n "${CONFIG_BPF}" ]; then
 	${RESOLVE_BTFIDS} vmlinux
 fi
 
+info SYSMAP System.map
+mksysmap vmlinux System.map
+
 if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
 	info SORTTAB vmlinux
 	if ! sorttable vmlinux; then
@@ -408,9 +411,6 @@ if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
 	fi
 fi
 
-info SYSMAP System.map
-mksysmap vmlinux System.map
-
 # step a (see comment above)
 if [ -n "${CONFIG_KALLSYMS}" ]; then
 	mksysmap ${kallsyms_vmlinux} .tmp_System.map
diff --git a/scripts/sorttable.c b/scripts/sorttable.c
index b7c2ad71f9cf..70bdc787ddfb 100644
--- a/scripts/sorttable.c
+++ b/scripts/sorttable.c
@@ -30,6 +30,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <errno.h>
+#include <pthread.h>
 
 #include <tools/be_byteshift.h>
 #include <tools/le_byteshift.h>
diff --git a/scripts/sorttable.h b/scripts/sorttable.h
index a2baa2fefb13..0743fb58812d 100644
--- a/scripts/sorttable.h
+++ b/scripts/sorttable.h
@@ -19,6 +19,9 @@
 
 #undef extable_ent_size
 #undef compare_extable
+#undef get_mcount_loc
+#undef sort_mcount_loc
+#undef elf_mcount_loc
 #undef do_sort
 #undef Elf_Addr
 #undef Elf_Ehdr
@@ -41,6 +44,9 @@
 #ifdef SORTTABLE_64
 # define extable_ent_size	16
 # define compare_extable	compare_extable_64
+# define get_mcount_loc    get_mcount_loc_64
+# define sort_mcount_loc    sort_mcount_loc_64
+# define elf_mcount_loc     elf_mcount_loc_64
 # define do_sort		do_sort_64
 # define Elf_Addr		Elf64_Addr
 # define Elf_Ehdr		Elf64_Ehdr
@@ -62,6 +68,9 @@
 #else
 # define extable_ent_size	8
 # define compare_extable	compare_extable_32
+# define get_mcount_loc    get_mcount_loc_32
+# define sort_mcount_loc    sort_mcount_loc_32
+# define elf_mcount_loc     elf_mcount_loc_32
 # define do_sort		do_sort_32
 # define Elf_Addr		Elf32_Addr
 # define Elf_Ehdr		Elf32_Ehdr
@@ -84,8 +93,6 @@
 
 #if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
 /* ORC unwinder only support X86_64 */
-#include <errno.h>
-#include <pthread.h>
 #include <asm/orc_types.h>
 
 #define ERRSTR_MAXSZ	256
@@ -191,6 +198,62 @@ static int compare_extable(const void *a, const void *b)
 		return 1;
 	return 0;
 }
+struct elf_mcount_loc {
+	Elf_Ehdr *ehdr;
+	Elf_Shdr *init_data_sec;
+	uint_t start_mcount_loc;
+	uint_t stop_mcount_loc;
+};
+
+/* Sort the addresses stored between __start_mcount_loc to __stop_mcount_loc in vmlinux */
+static void *sort_mcount_loc(void *arg)
+{
+	struct elf_mcount_loc *emloc = (struct elf_mcount_loc *)arg;
+	uint_t offset = emloc->start_mcount_loc - _r(&(emloc->init_data_sec)->sh_addr)
+					+ _r(&(emloc->init_data_sec)->sh_offset);
+	uint_t count = emloc->stop_mcount_loc - emloc->start_mcount_loc;
+	unsigned char *start_loc = (void *)emloc->ehdr + offset;
+
+	qsort(start_loc, count/sizeof(uint_t), sizeof(uint_t), compare_extable);
+	return NULL;
+}
+
+/* Get the address of __start_mcount_loc and __stop_mcount_loc in System.map */
+static void get_mcount_loc(uint_t *_start, uint_t *_stop)
+{
+	FILE *file_start, *file_stop;
+	char start_buff[20];
+	char stop_buff[20];
+	int len = 0;
+
+	file_start = popen(" grep start_mcount System.map | awk '{print $1}' ", "r");
+	if (!file_start) {
+		fprintf(stderr, "get start_mcount_loc error!");
+		return;
+	}
+
+	file_stop = popen(" grep stop_mcount System.map | awk '{print $1}' ", "r");
+	if (!file_stop) {
+		fprintf(stderr, "get stop_mcount_loc error!");
+		pclose(file_start);
+		return;
+	}
+
+	while (fgets(start_buff, sizeof(start_buff), file_start) != NULL) {
+		len = strlen(start_buff);
+		start_buff[len - 1] = '\0';
+	}
+	*_start = strtoul(start_buff, NULL, 16);
+
+	while (fgets(stop_buff, sizeof(stop_buff), file_stop) != NULL) {
+		len = strlen(stop_buff);
+		stop_buff[len - 1] = '\0';
+	}
+	*_stop = strtoul(stop_buff, NULL, 16);
+
+	pclose(file_start);
+	pclose(file_stop);
+}
 
 static int do_sort(Elf_Ehdr *ehdr,
 		   char const *const fname,
@@ -217,6 +280,10 @@ static int do_sort(Elf_Ehdr *ehdr,
 	int idx;
 	unsigned int shnum;
 	unsigned int shstrndx;
+	struct elf_mcount_loc mstruct;
+	uint_t _start_mcount_loc = 0;
+	uint_t _stop_mcount_loc = 0;
+	pthread_t mcount_sort_thread;
 #if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
 	unsigned int orc_ip_size = 0;
 	unsigned int orc_size = 0;
@@ -253,6 +320,14 @@ static int do_sort(Elf_Ehdr *ehdr,
 			symtab_shndx = (Elf32_Word *)((const char *)ehdr +
 						      _r(&s->sh_offset));
 
+		/* locate the .init.data section in vmlinux */
+		if (!strcmp(secstrings + idx, ".init.data")) {
+			get_mcount_loc(&_start_mcount_loc, &_stop_mcount_loc);
+			mstruct.ehdr = ehdr;
+			mstruct.init_data_sec = s;
+			mstruct.start_mcount_loc = _start_mcount_loc;
+			mstruct.stop_mcount_loc = _stop_mcount_loc;
+		}
 #if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED)
 		/* locate the ORC unwind tables */
 		if (!strcmp(secstrings + idx, ".orc_unwind_ip")) {
@@ -294,6 +369,21 @@ static int do_sort(Elf_Ehdr *ehdr,
 		goto out;
 	}
 #endif
+	if (!mstruct.init_data_sec || !_start_mcount_loc || !_stop_mcount_loc) {
+		fprintf(stderr,
+			"incomplete mcount's sort in file: %s\n",
+			fname);
+		goto out;
+	}
+
+	/* create thread to sort mcount_loc concurrently */
+	if (pthread_create(&mcount_sort_thread, NULL, &sort_mcount_loc, &mstruct)) {
+		fprintf(stderr,
+			"pthread_create mcount_sort_thread failed '%s': %s\n",
+			strerror(errno), fname);
+		goto out;
+	}
+
 	if (!extab_sec) {
 		fprintf(stderr,	"no __ex_table in file: %s\n", fname);
 		goto out;
@@ -376,5 +466,20 @@ static int do_sort(Elf_Ehdr *ehdr,
 		}
 	}
 #endif
+	if (mcount_sort_thread) {
+		void *retval = NULL;
+		/* wait for mcount sort done */
+		rc = pthread_join(mcount_sort_thread, &retval);
+		if (rc)
+			fprintf(stderr,
+				"pthread_join failed '%s': %s\n",
+				strerror(errno), fname);
+		else if (retval) {
+			rc = -1;
+			fprintf(stderr,
+				"failed to sort mcount '%s': %s\n",
+				(char *)retval, fname);
+		}
+	}
 	return rc;
 }
-- 
2.14.4.44.g2045bb6