[PATCH v7c 20/24] dyndbg: refactor *dynamic_emit_prefix

Jim Cromie
2023-10-18T17:07:36Z

Refactor the split of duties between outer & inner fns.

The outer fn was previously just an inline unlikely forward to inner,
which did all the work.

Now, outer handles +t and +l flags itself, and calls inner only when
_DPRINTK_FLAGS_INCL_LOOKUP is needed.

No functional change.

But it does make the results of the inner-fn more cache-friendly
(fewer entries, reused more often):

1- no spurious [TID] or <intr> noise
2- no LINE-number to bloat the cache (avg 9 pr_debugs/fn)
3- only LOOKUP stuff

Currently LOOKUPs are descriptor-field refs but could be replaced by
accessor functions. This would allow the __dyndbg_sites section to be
de-duplicated and reclaimed; currently module, filename fields are
~90% repeated. As the accessors get more expensive, the value of
caching part of the prefix goes up.

Also change inner-fn to return count of extra chars written to the
buffer, and drop "inline" from outer, let the compiler decide. Maybe
also change name accordingly.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
fixup whitespace
---
lib/dynamic_debug.c | 39 ++++++++++++++++++++++-----------------
1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index a6ee142668bf..9db797a0cf82 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -774,11 +774,28 @@ static int remaining(int wrote)
return 0;
}

-static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+static int __dynamic_emit_prefix(const struct _ddebug *desc, char *buf, int pos)
+{
+ if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
+ pos += snprintf(buf + pos, remaining(pos), "%s:",
+ desc->modname);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
+ pos += snprintf(buf + pos, remaining(pos), "%s:",
+ desc->function);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_SOURCENAME)
+ pos += snprintf(buf + pos, remaining(pos), "%s:",
+ trim_prefix(desc->filename));
+ return pos;
+}
+
+static char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
{
int pos_after_tid;
int pos = 0;

+ if (likely(!(desc->flags & _DPRINTK_FLAGS_INCL_ANY)))
+ return buf;
+
if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
if (in_interrupt())
pos += snprintf(buf + pos, remaining(pos), "<intr> ");
@@ -787,15 +804,10 @@ static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
task_pid_vnr(current));
}
pos_after_tid = pos;
- if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
- pos += snprintf(buf + pos, remaining(pos), "%s:",
- desc->modname);
- if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
- pos += snprintf(buf + pos, remaining(pos), "%s:",
- desc->function);
- if (desc->flags & _DPRINTK_FLAGS_INCL_SOURCENAME)
- pos += snprintf(buf + pos, remaining(pos), "%s:",
- trim_prefix(desc->filename));
+
+ if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_LOOKUP))
+ pos += __dynamic_emit_prefix(desc, buf, pos);
+
if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
pos += snprintf(buf + pos, remaining(pos), "%d:",
desc->lineno);
@@ -807,13 +819,6 @@ 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;
--
2.41.0