Messages in this thread | | | Date | Fri, 7 Aug 2009 22:26:31 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH] perfcounters: Support for ftrace event records sampling |
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On Fri, Aug 07, 2009 at 12:37:57PM +0200, Peter Zijlstra wrote: > 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;
Ok. Yeah that's far more generic (and typed).
> > > @@ -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?
Yeah, I'll try to fix this by storing strings as pointers and copy them in perf counter output only.
TODO-listed, with all the above.
> > + > > +#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.
Indeed.
> > > 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?
Sorry, I added the explicit PERF_SAMPLE_TP_RECORD here to test this patch and forgot the newline when I removed it :-s
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