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Message-ID: <20241001214307.262550910@goodmis.org>
Date: Tue, 01 Oct 2024 17:42:44 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jiri Olsa <olsajiri@...il.com>
Subject: [for-next][PATCH 3/5] fgraph: Use fgraph data to store subtime for profiler
From: Steven Rostedt <rostedt@...dmis.org>
Instead of having the "subtime" for the function profiler in the
infrastructure ftrace_ret_stack structure, have it use the fgraph data
reserve and retrieve functions.
This will keep the limited shadow stack from wasting 8 bytes for something
that is seldom used.
Cc: Mark Rutland <mark.rutland@....com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jiri Olsa <olsajiri@...il.com>
Link: https://lore.kernel.org/20240914214826.780323141@goodmis.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
include/linux/ftrace.h | 4 +--
kernel/trace/fgraph.c | 64 ++++++++++++++++++++++++++++++++----------
kernel/trace/ftrace.c | 23 +++++++--------
3 files changed, 62 insertions(+), 29 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 42106b3de396..aabd348cad4a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1081,6 +1081,7 @@ struct fgraph_ops {
void *fgraph_reserve_data(int idx, int size_bytes);
void *fgraph_retrieve_data(int idx, int *size_bytes);
+void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth);
/*
* Stack of return addresses for functions
@@ -1091,9 +1092,6 @@ struct ftrace_ret_stack {
unsigned long ret;
unsigned long func;
unsigned long long calltime;
-#ifdef CONFIG_FUNCTION_PROFILER
- unsigned long long subtime;
-#endif
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
unsigned long fp;
#endif
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index d7d4fb403f6f..095ceb752b28 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -390,21 +390,7 @@ void *fgraph_reserve_data(int idx, int size_bytes)
*/
void *fgraph_retrieve_data(int idx, int *size_bytes)
{
- int offset = current->curr_ret_stack - 1;
- unsigned long val;
-
- val = get_fgraph_entry(current, offset);
- while (__get_type(val) == FGRAPH_TYPE_DATA) {
- if (__get_data_index(val) == idx)
- goto found;
- offset -= __get_data_size(val) + 1;
- val = get_fgraph_entry(current, offset);
- }
- return NULL;
-found:
- if (size_bytes)
- *size_bytes = __get_data_size(val) * sizeof(long);
- return get_data_type_data(current, offset);
+ return fgraph_retrieve_parent_data(idx, size_bytes, 0);
}
/**
@@ -460,6 +446,54 @@ get_ret_stack(struct task_struct *t, int offset, int *frame_offset)
return RET_STACK(t, offset);
}
+/**
+ * fgraph_retrieve_parent_data - get data from a parent function
+ * @idx: The index into the fgraph_array (fgraph_ops::idx)
+ * @size_bytes: A pointer to retrieved data size
+ * @depth: The depth to find the parent (0 is the current function)
+ *
+ * This is similar to fgraph_retrieve_data() but can be used to retrieve
+ * data from a parent caller function.
+ *
+ * Return: a pointer to the specified parent data or NULL if not found
+ */
+void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth)
+{
+ struct ftrace_ret_stack *ret_stack = NULL;
+ int offset = current->curr_ret_stack;
+ unsigned long val;
+
+ if (offset <= 0)
+ return NULL;
+
+ for (;;) {
+ int next_offset;
+
+ ret_stack = get_ret_stack(current, offset, &next_offset);
+ if (!ret_stack || --depth < 0)
+ break;
+ offset = next_offset;
+ }
+
+ if (!ret_stack)
+ return NULL;
+
+ offset--;
+
+ val = get_fgraph_entry(current, offset);
+ while (__get_type(val) == FGRAPH_TYPE_DATA) {
+ if (__get_data_index(val) == idx)
+ goto found;
+ offset -= __get_data_size(val) + 1;
+ val = get_fgraph_entry(current, offset);
+ }
+ return NULL;
+found:
+ if (size_bytes)
+ *size_bytes = __get_data_size(val) * sizeof(long);
+ return get_data_type_data(current, offset);
+}
+
/* Both enabled by default (can be cleared by function_graph tracer flags */
static bool fgraph_sleep_time = true;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d2dd71d04b8a..bac1f2ee1983 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -823,7 +823,7 @@ void ftrace_graph_graph_time_control(bool enable)
static int profile_graph_entry(struct ftrace_graph_ent *trace,
struct fgraph_ops *gops)
{
- struct ftrace_ret_stack *ret_stack;
+ unsigned long long *subtime;
function_profile_call(trace->func, 0, NULL, NULL);
@@ -831,9 +831,9 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace,
if (!current->ret_stack)
return 0;
- ret_stack = ftrace_graph_get_ret_stack(current, 0);
- if (ret_stack)
- ret_stack->subtime = 0;
+ subtime = fgraph_reserve_data(gops->idx, sizeof(*subtime));
+ if (subtime)
+ *subtime = 0;
return 1;
}
@@ -841,11 +841,12 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace,
static void profile_graph_return(struct ftrace_graph_ret *trace,
struct fgraph_ops *gops)
{
- struct ftrace_ret_stack *ret_stack;
struct ftrace_profile_stat *stat;
unsigned long long calltime;
+ unsigned long long *subtime;
struct ftrace_profile *rec;
unsigned long flags;
+ int size;
local_irq_save(flags);
stat = this_cpu_ptr(&ftrace_profile_stats);
@@ -861,13 +862,13 @@ static void profile_graph_return(struct ftrace_graph_ret *trace,
if (!fgraph_graph_time) {
/* Append this call time to the parent time to subtract */
- ret_stack = ftrace_graph_get_ret_stack(current, 1);
- if (ret_stack)
- ret_stack->subtime += calltime;
+ subtime = fgraph_retrieve_parent_data(gops->idx, &size, 1);
+ if (subtime)
+ *subtime += calltime;
- ret_stack = ftrace_graph_get_ret_stack(current, 0);
- if (ret_stack && ret_stack->subtime < calltime)
- calltime -= ret_stack->subtime;
+ subtime = fgraph_retrieve_data(gops->idx, &size);
+ if (subtime && *subtime && *subtime < calltime)
+ calltime -= *subtime;
else
calltime = 0;
}
--
2.45.2
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