Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 7 Jun 2016 22:49:15 +0900 | Subject | Re: [RFC/PATCH] ftrace: Reduce size of function graph entries |
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Hi Steve,
Could you please take a look at this?
Thanks, Namhyung
On Mon, May 23, 2016 at 12:26 AM, Namhyung Kim <namhyung@kernel.org> wrote: > 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 some archs can have efficient unaligned > accesses, reducing the alignment can save ~10% of data size: > > 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. Tested on x86_64 only. > > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- > include/linux/ftrace.h | 16 ++++++++++++---- > kernel/trace/trace.h | 11 +++++++++++ > kernel/trace/trace_entries.h | 4 ++-- > 3 files changed, 25 insertions(+), 6 deletions(-) > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index dea12a6e413b..35c523ba5c59 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -751,25 +751,33 @@ extern void ftrace_init(void); > static inline void ftrace_init(void) { } > #endif > > +#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS > +# define FTRACE_ALIGNMENT 4 > +#else > +# define FTRACE_ALIGNMENT 8 > +#endif > + > +#define FTRACE_ALIGN_DATA __attribute__((packed, aligned(FTRACE_ALIGNMENT))) > + > /* > * Structure that defines an entry function trace. > */ > struct ftrace_graph_ent { > unsigned long func; /* Current function */ > int depth; > -}; > +} FTRACE_ALIGN_DATA; > > /* > * Structure that defines a return function trace. > */ > 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; > -}; > +} FTRACE_ALIGN_DATA; > > /* 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 5167c366d6b7..d2dd49ca55ee 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) FTRACE_ALIGN_DATA > + > #include "trace_entries.h" > > /* > @@ -1600,6 +1606,11 @@ 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, > > -- > 2.8.0 >
-- Thanks, Namhyung
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