Re: [PATCH v9 36/36] fgraph: Skip recording calltime/rettime if it is not nneeded
On Thu, 25 Apr 2024 13:15:08 -0700 Andrii Nakryiko wrote: > On Mon, Apr 15, 2024 at 6:25 AM Masami Hiramatsu (Google) > wrote: > > > > From: Masami Hiramatsu (Google) > > > > Skip recording calltime and rettime if the fgraph_ops does not need it. > > This is a kind of performance optimization for fprobe. Since the fprobe > > user does not use these entries, recording timestamp in fgraph is just > > a overhead (e.g. eBPF, ftrace). So introduce the skip_timestamp flag, > > and all fgraph_ops sets this flag, skip recording calltime and rettime. > > > > Suggested-by: Jiri Olsa > > Signed-off-by: Masami Hiramatsu (Google) > > --- > > Changes in v9: > > - Newly added. > > --- > > include/linux/ftrace.h |2 ++ > > kernel/trace/fgraph.c | 46 > > +++--- > > kernel/trace/fprobe.c |1 + > > 3 files changed, 42 insertions(+), 7 deletions(-) > > > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > > index d845a80a3d56..06fc7cbef897 100644 > > --- a/include/linux/ftrace.h > > +++ b/include/linux/ftrace.h > > @@ -1156,6 +1156,8 @@ struct fgraph_ops { > > struct ftrace_ops ops; /* for the hash lists */ > > void*private; > > int idx; > > + /* If skip_timestamp is true, this does not record timestamps. */ > > + boolskip_timestamp; > > }; > > > > void *fgraph_reserve_data(int idx, int size_bytes); > > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > > index 7556fbbae323..a5722537bb79 100644 > > --- a/kernel/trace/fgraph.c > > +++ b/kernel/trace/fgraph.c > > @@ -131,6 +131,7 @@ DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); > > int ftrace_graph_active; > > > > static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; > > +static bool fgraph_skip_timestamp; > > > > /* LRU index table for fgraph_array */ > > static int fgraph_lru_table[FGRAPH_ARRAY_SIZE]; > > @@ -475,7 +476,7 @@ void ftrace_graph_stop(void) > > static int > > ftrace_push_return_trace(unsigned long ret, unsigned long func, > > unsigned long frame_pointer, unsigned long *retp, > > -int fgraph_idx) > > +int fgraph_idx, bool skip_ts) > > { > > struct ftrace_ret_stack *ret_stack; > > unsigned long long calltime; > > @@ -498,8 +499,12 @@ ftrace_push_return_trace(unsigned long ret, unsigned > > long func, > > ret_stack = get_ret_stack(current, current->curr_ret_stack, ); > > if (ret_stack && ret_stack->func == func && > > get_fgraph_type(current, index + FGRAPH_RET_INDEX) == > > FGRAPH_TYPE_BITMAP && > > - !is_fgraph_index_set(current, index + FGRAPH_RET_INDEX, > > fgraph_idx)) > > + !is_fgraph_index_set(current, index + FGRAPH_RET_INDEX, > > fgraph_idx)) { > > + /* If previous one skips calltime, update it. */ > > + if (!skip_ts && !ret_stack->calltime) > > + ret_stack->calltime = trace_clock_local(); > > return index + FGRAPH_RET_INDEX; > > + } > > > > val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | > > FGRAPH_RET_INDEX; > > > > @@ -517,7 +522,10 @@ ftrace_push_return_trace(unsigned long ret, unsigned > > long func, > > return -EBUSY; > > } > > > > - calltime = trace_clock_local(); > > + if (skip_ts) > > would it be ok to add likely() here to keep the least-overhead code path > linear? It's not "likely", but hmm, yes as you said. We can keep the least overhead. OK, let me add likely. Thank you, > > > + calltime = 0LL; > > + else > > + calltime = trace_clock_local(); > > > > index = READ_ONCE(current->curr_ret_stack); > > ret_stack = RET_STACK(current, index); > > @@ -601,7 +609,8 @@ int function_graph_enter_regs(unsigned long ret, > > unsigned long func, > > trace.func = func; > > trace.depth = ++current->curr_ret_depth; > > > > - index = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0); > > + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0, > > +fgraph_skip_timestamp); > > if (index < 0) > > goto out; > > > > @@ -654,7 +663,8 @@ int function_graph_enter_ops(unsigned long ret, > > unsigned long func, > > return -ENODEV; > > > > /* Use start for the distance to ret_stack (skipping over reserve) > > */ > > - index = ftrace_push_return_trace(ret, func, frame_pointer, retp, > > gops->idx); > > + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, > > gops->idx, > > +gops->skip_timestamp); > > if (index < 0) > > return index; > > type = get_fgraph_type(current, index); > > @@ -732,6
Re: [PATCH v9 36/36] fgraph: Skip recording calltime/rettime if it is not nneeded
On Mon, Apr 15, 2024 at 6:25 AM Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) > > Skip recording calltime and rettime if the fgraph_ops does not need it. > This is a kind of performance optimization for fprobe. Since the fprobe > user does not use these entries, recording timestamp in fgraph is just > a overhead (e.g. eBPF, ftrace). So introduce the skip_timestamp flag, > and all fgraph_ops sets this flag, skip recording calltime and rettime. > > Suggested-by: Jiri Olsa > Signed-off-by: Masami Hiramatsu (Google) > --- > Changes in v9: > - Newly added. > --- > include/linux/ftrace.h |2 ++ > kernel/trace/fgraph.c | 46 +++--- > kernel/trace/fprobe.c |1 + > 3 files changed, 42 insertions(+), 7 deletions(-) > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index d845a80a3d56..06fc7cbef897 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -1156,6 +1156,8 @@ struct fgraph_ops { > struct ftrace_ops ops; /* for the hash lists */ > void*private; > int idx; > + /* If skip_timestamp is true, this does not record timestamps. */ > + boolskip_timestamp; > }; > > void *fgraph_reserve_data(int idx, int size_bytes); > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index 7556fbbae323..a5722537bb79 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -131,6 +131,7 @@ DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); > int ftrace_graph_active; > > static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; > +static bool fgraph_skip_timestamp; > > /* LRU index table for fgraph_array */ > static int fgraph_lru_table[FGRAPH_ARRAY_SIZE]; > @@ -475,7 +476,7 @@ void ftrace_graph_stop(void) > static int > ftrace_push_return_trace(unsigned long ret, unsigned long func, > unsigned long frame_pointer, unsigned long *retp, > -int fgraph_idx) > +int fgraph_idx, bool skip_ts) > { > struct ftrace_ret_stack *ret_stack; > unsigned long long calltime; > @@ -498,8 +499,12 @@ ftrace_push_return_trace(unsigned long ret, unsigned > long func, > ret_stack = get_ret_stack(current, current->curr_ret_stack, ); > if (ret_stack && ret_stack->func == func && > get_fgraph_type(current, index + FGRAPH_RET_INDEX) == > FGRAPH_TYPE_BITMAP && > - !is_fgraph_index_set(current, index + FGRAPH_RET_INDEX, > fgraph_idx)) > + !is_fgraph_index_set(current, index + FGRAPH_RET_INDEX, > fgraph_idx)) { > + /* If previous one skips calltime, update it. */ > + if (!skip_ts && !ret_stack->calltime) > + ret_stack->calltime = trace_clock_local(); > return index + FGRAPH_RET_INDEX; > + } > > val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_RET_INDEX; > > @@ -517,7 +522,10 @@ ftrace_push_return_trace(unsigned long ret, unsigned > long func, > return -EBUSY; > } > > - calltime = trace_clock_local(); > + if (skip_ts) would it be ok to add likely() here to keep the least-overhead code path linear? > + calltime = 0LL; > + else > + calltime = trace_clock_local(); > > index = READ_ONCE(current->curr_ret_stack); > ret_stack = RET_STACK(current, index); > @@ -601,7 +609,8 @@ int function_graph_enter_regs(unsigned long ret, unsigned > long func, > trace.func = func; > trace.depth = ++current->curr_ret_depth; > > - index = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0); > + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0, > +fgraph_skip_timestamp); > if (index < 0) > goto out; > > @@ -654,7 +663,8 @@ int function_graph_enter_ops(unsigned long ret, unsigned > long func, > return -ENODEV; > > /* Use start for the distance to ret_stack (skipping over reserve) */ > - index = ftrace_push_return_trace(ret, func, frame_pointer, retp, > gops->idx); > + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, > gops->idx, > +gops->skip_timestamp); > if (index < 0) > return index; > type = get_fgraph_type(current, index); > @@ -732,6 +742,7 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, > unsigned long *ret, > *ret = ret_stack->ret; > trace->func = ret_stack->func; > trace->calltime = ret_stack->calltime; > + trace->rettime = 0; > trace->overrun = atomic_read(>trace_overrun); > trace->depth = current->curr_ret_depth; > /* > @@ -792,7 +803,6 @@ __ftrace_return_to_handler(struct