[RFC PATCH v6 01/34] dyndbg: avoid calling dyndbg_emit_prefix when it has no work

Jim Cromie
2021-05-29T20:02:06Z

Wrap function in a static-inline one, which checks flags to avoid
calling the function unnecessarily.

And hoist its output-buffer initialization to the grand-caller, which
is already allocating the buffer on the stack, and can trivially
initialize it too.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/linux/dynamic_debug.h | 5 +++++
lib/dynamic_debug.c | 19 ++++++++++++-------
2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index a57ee75342cf..dce631e678dd 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -32,6 +32,11 @@ struct _ddebug {
#define _DPRINTK_FLAGS_INCL_FUNCNAME (1<<2)
#define _DPRINTK_FLAGS_INCL_LINENO (1<<3)
#define _DPRINTK_FLAGS_INCL_TID (1<<4)
+
+#define _DPRINTK_FLAGS_INCL_ANY \
+ (_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
+ _DPRINTK_FLAGS_INCL_LINENO | _DPRINTK_FLAGS_INCL_TID)
+
#if defined DEBUG
#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
#else
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c70d6347afa2..ede4a491ee87 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -586,13 +586,11 @@ static int remaining(int wrote)
return 0;
}

-static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
{
int pos_after_tid;
int pos = 0;

- *buf = '\0';
-
if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
if (in_interrupt())
pos += snprintf(buf + pos, remaining(pos), "<intr> ");
@@ -618,11 +616,18 @@ static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
return buf;
}

+static inline char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
+{
+ if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_ANY))
+ return __dynamic_emit_prefix(desc, buf);
+ return buf;
+}
+
void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
{
va_list args;
struct va_format vaf;
- char buf[PREFIX_SIZE];
+ char buf[PREFIX_SIZE] = "";

BUG_ON(!descriptor);
BUG_ON(!fmt);
@@ -655,7 +660,7 @@ void __dynamic_dev_dbg(struct _ddebug *descriptor,
if (!dev) {
printk(KERN_DEBUG "(NULL device *): %pV", &vaf);
} else {
- char buf[PREFIX_SIZE];
+ char buf[PREFIX_SIZE] = "";

dev_printk_emit(LOGLEVEL_DEBUG, dev, "%s%s %s: %pV",
dynamic_emit_prefix(descriptor, buf),
@@ -684,7 +689,7 @@ void __dynamic_netdev_dbg(struct _ddebug *descriptor,
vaf.va = &args;

if (dev && dev->dev.parent) {
- char buf[PREFIX_SIZE];
+ char buf[PREFIX_SIZE] = "";

dev_printk_emit(LOGLEVEL_DEBUG, dev->dev.parent,
"%s%s %s %s%s: %pV",
@@ -720,7 +725,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
vaf.va = &args;

if (ibdev && ibdev->dev.parent) {
- char buf[PREFIX_SIZE];
+ char buf[PREFIX_SIZE] = "";

dev_printk_emit(LOGLEVEL_DEBUG, ibdev->dev.parent,
"%s%s %s %s: %pV",
--
2.31.1