From: Namhyung Kim Currently ftrace_graph_ent{,_entry} and ftrace_graph_ret{,_entry} struct can have padding bytes at the end due to alignment in 64-bit data type. As these data are recorded so frequently, those paddings waste non-negligible space. As the ring buffer maintains alignment properly for each architecture, just to remove the extra padding using 'packed' attribute. ftrace_graph_ent_entry: 24 -> 20 ftrace_graph_ret_entry: 48 -> 44 Also I moved the 'overrun' field in struct ftrace_graph_ret to minimize the padding in the middle. Tested on x86_64 only. Link: http://lkml.kernel.org/r/1467197808-13578-1-git-send-email-namhyung@kernel.org Cc: Ingo Molnar Cc: linux-arch@vger.kernel.org Signed-off-by: Namhyung Kim Signed-off-by: Steven Rostedt --- include/linux/ftrace.h | 12 ++++++++---- kernel/trace/trace.h | 11 +++++++++++ kernel/trace/trace_entries.h | 4 ++-- 3 files changed, 21 insertions(+), 6 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 66a36a815f0a..7d565afe35d2 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -754,23 +754,27 @@ static inline void ftrace_init(void) { } /* * Structure that defines an entry function trace. + * It's already packed but the attribute "packed" is needed + * to remove extra padding at the end. */ struct ftrace_graph_ent { unsigned long func; /* Current function */ int depth; -}; +} __packed; /* * Structure that defines a return function trace. + * It's already packed but the attribute "packed" is needed + * to remove extra padding at the end. */ struct ftrace_graph_ret { unsigned long func; /* Current function */ - unsigned long long calltime; - unsigned long long rettime; /* Number of functions that overran the depth limit for current task */ unsigned long overrun; + unsigned long long calltime; + unsigned long long rettime; int depth; -}; +} __packed; /* Type of the callback handlers for tracing function graph*/ typedef void (*trace_func_graph_ret_t)(struct ftrace_graph_ret *); /* return */ diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index c1de3f493cd3..f783df416726 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -80,6 +80,12 @@ enum trace_type { FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print), \ filter) +#undef FTRACE_ENTRY_PACKED +#define FTRACE_ENTRY_PACKED(name, struct_name, id, tstruct, print, \ + filter) \ + FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print), \ + filter) __packed + #include "trace_entries.h" /* @@ -1625,6 +1631,11 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled); #define FTRACE_ENTRY_DUP(call, struct_name, id, tstruct, print, filter) \ FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print), \ filter) +#undef FTRACE_ENTRY_PACKED +#define FTRACE_ENTRY_PACKED(call, struct_name, id, tstruct, print, filter) \ + FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print), \ + filter) + #include "trace_entries.h" #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_FUNCTION_TRACER) diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index ee7b94a4810a..5c30efcda5e6 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -72,7 +72,7 @@ FTRACE_ENTRY_REG(function, ftrace_entry, ); /* Function call entry */ -FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry, +FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry, TRACE_GRAPH_ENT, @@ -88,7 +88,7 @@ FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry, ); /* Function return entry */ -FTRACE_ENTRY(funcgraph_exit, ftrace_graph_ret_entry, +FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, TRACE_GRAPH_RET, -- 2.8.1