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fgraph: Use fgraph data to store subtime for profiler

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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@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Link: https://lore.kernel.org/20240914214826.780323141@goodmis.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2024-09-14 17:48:06 -04:00 committed by Steven Rostedt (Google)
parent a370b72ec7
commit a312a0f783
3 changed files with 62 additions and 29 deletions
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4
include/linux/ftrace.h
View File

@ -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

64
kernel/trace/fgraph.c
View File

@ -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;

23
kernel/trace/ftrace.c
View File

@ -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;
}