Messages in this thread Patch in this message | | | Subject | Re: [PATCH] perfcounters: Support for ftrace event records sampling | From | Peter Zijlstra <> | Date | Fri, 07 Aug 2009 12:37:57 +0200 |
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On Fri, 2009-08-07 at 01:25 +0200, Frederic Weisbecker wrote: > This patch brings the kernel side support for ftrace event record > sampling. > > A new counter attribute is added: PERF_SAMPLE_TP_RECORD which requests > ftrace events record sampling. >
> + PERF_SAMPLE_TP_RECORD = 1U << 10,
I'd really want this thing called PERF_SAMPLE_RAW
> - PERF_SAMPLE_MAX = 1U << 10, /* non-ABI */ > + PERF_SAMPLE_MAX = 1U << 11, /* non-ABI */ > }; > > /* > @@ -413,6 +414,11 @@ struct perf_callchain_entry { > __u64 ip[PERF_MAX_STACK_DEPTH]; > }; > > +struct perf_tracepoint_record { > + int size; > + char *record; > +};
Which would make this:
struct perf_raw_record { u32 size; void *data; };
> struct task_struct; > > /** > @@ -681,6 +687,7 @@ struct perf_sample_data { > struct pt_regs *regs; > u64 addr; > u64 period; > + void *private; > };
might as well make that struct perf_raw_record *raw;
> @@ -649,5 +617,99 @@ __attribute__((section("_ftrace_events"))) event_##call = { \ > > #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) > > +/* > + * Define the insertion callback to profile events > + * > + * The job is very similar to ftrace_raw_event_<call> except that we don't > + * insert in the ring buffer but in a perf counter. > + * > + * static void ftrace_profile_<call>(proto) > + * { > + * struct ftrace_data_offsets_<call> __maybe_unused __data_offsets; > + * struct ftrace_event_call *event_call = &event_<call>; > + * extern void perf_tpcounter_event(int, u64, u64, void *, int); > + * struct ftrace_raw_##call *entry; > + * u64 __addr = 0, __count = 1; > + * unsigned long irq_flags; > + * int __entry_size; > + * int __data_size; > + * int pc; > + * > + * local_save_flags(irq_flags); > + * pc = preempt_count(); > + * > + * __data_size = ftrace_get_offsets_<call>(&__data_offsets, args); > + * __entry_size = __data_size + sizeof(*entry); > + * > + * do { > + * char raw_data[__entry_size]; <- allocate our sample in the stack > + * struct trace_entry *ent; > + * > + * entry = (struct ftrace_raw_<call> *)raw_data; > + * ent = &entry->ent; > + * tracing_generic_entry_update(ent, irq_flags, pc); > + * ent->type = event_call->id; > + * > + * <tstruct> <- do some jobs with dynamic arrays > + * > + * <assign> <- affect our values > + * > + * perf_tpcounter_event(event_call->id, __addr, __count, entry, > + * __entry_size); <- submit them to perf counter > + * } while (0); > + * > + * } > + */ > + > +#ifdef CONFIG_EVENT_PROFILE > + > +#undef __perf_addr > +#define __perf_addr(a) __addr = (a) > + > +#undef __perf_count > +#define __perf_count(c) __count = (c) > + > +#undef TRACE_EVENT > +#define TRACE_EVENT(call, proto, args, tstruct, assign, print) \ > +static void ftrace_profile_##call(proto) \ > +{ \ > + struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\ > + struct ftrace_event_call *event_call = &event_##call; \ > + extern void perf_tpcounter_event(int, u64, u64, void *, int); \ > + struct ftrace_raw_##call *entry; \ > + u64 __addr = 0, __count = 1; \ > + unsigned long irq_flags; \ > + int __entry_size; \ > + int __data_size; \ > + int pc; \ > + \ > + local_save_flags(irq_flags); \ > + pc = preempt_count(); \ > + \ > + __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \ > + __entry_size = __data_size + sizeof(*entry); \ > + \ > + do { \ > + char raw_data[__entry_size]; \ > + struct trace_entry *ent; \ > + \ > + entry = (struct ftrace_raw_##call *)raw_data; \ > + ent = &entry->ent; \ > + tracing_generic_entry_update(ent, irq_flags, pc); \ > + ent->type = event_call->id; \ > + \ > + tstruct \ > + \ > + { assign; } \ > + \ > + perf_tpcounter_event(event_call->id, __addr, __count, entry,\ > + __entry_size); \ > + } while (0); \ > + \ > +}
ok, so the one concern I have here is that the data needs to fit on the stack. What if someone puts a large string in the data?
> + > +#include TRACE_INCLUDE(TRACE_INCLUDE_FILE) > +#endif /* CONFIG_EVENT_PROFILE */ > + > #undef _TRACE_PROFILE_INIT > > diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c > index 06d210c..93f4312 100644 > --- a/kernel/perf_counter.c > +++ b/kernel/perf_counter.c > @@ -2646,6 +2646,7 @@ static void perf_counter_output(struct perf_counter *counter, int nmi, > u64 counter; > } group_entry; > struct perf_callchain_entry *callchain = NULL; > + struct perf_tracepoint_record *tp; > int callchain_size = 0; > u64 time; > struct { > @@ -2714,6 +2715,11 @@ static void perf_counter_output(struct perf_counter *counter, int nmi, > header.size += sizeof(u64); > } > > + if (sample_type & PERF_SAMPLE_TP_RECORD) { > + tp = data->private; > + header.size += tp->size; > + } > + > ret = perf_output_begin(&handle, counter, header.size, nmi, 1); > if (ret) > return; > @@ -2777,6 +2783,9 @@ static void perf_counter_output(struct perf_counter *counter, int nmi, > } > } > > + if (sample_type & PERF_SAMPLE_TP_RECORD) > + perf_output_copy(&handle, tp->record, tp->size); > + > perf_output_end(&handle); > }
You seem to fail to round up to a multiple of u64 somewhere along the line, that'll mess things up as events are supposed to be u64 aligned.
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > index 6da0992..90c9808 100644 > --- a/tools/perf/builtin-record.c > +++ b/tools/perf/builtin-record.c > @@ -412,6 +412,7 @@ static void create_counter(int counter, int cpu, pid_t pid) > if (call_graph) > attr->sample_type |= PERF_SAMPLE_CALLCHAIN; > > + > attr->mmap = track; > attr->comm = track; > attr->inherit = (cpu < 0) && inherit;
Do we really need that extra whitespace?
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