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Date:	Thu, 23 Oct 2014 17:51:27 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 04/16] perf tools: Add a thread stack for synthesizing
 call chains

Em Thu, Oct 23, 2014 at 01:45:12PM +0300, Adrian Hunter escreveu:
> Add a thread stack for synthesizing call chains from call
> and return events.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/Makefile.perf       |   2 +
>  tools/perf/util/event.h        |  26 +++++++
>  tools/perf/util/thread-stack.c | 151 +++++++++++++++++++++++++++++++++++++++++
>  tools/perf/util/thread-stack.h |  32 +++++++++
>  tools/perf/util/thread.c       |   3 +
>  tools/perf/util/thread.h       |   3 +
>  6 files changed, 217 insertions(+)
>  create mode 100644 tools/perf/util/thread-stack.c
>  create mode 100644 tools/perf/util/thread-stack.h
> 
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 262916f..5bbe1ff 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -304,6 +304,7 @@ LIB_H += ui/util.h
>  LIB_H += ui/ui.h
>  LIB_H += util/data.h
>  LIB_H += util/kvm-stat.h
> +LIB_H += util/thread-stack.h
>  
>  LIB_OBJS += $(OUTPUT)util/abspath.o
>  LIB_OBJS += $(OUTPUT)util/alias.o
> @@ -380,6 +381,7 @@ LIB_OBJS += $(OUTPUT)util/srcline.o
>  LIB_OBJS += $(OUTPUT)util/data.o
>  LIB_OBJS += $(OUTPUT)util/tsc.o
>  LIB_OBJS += $(OUTPUT)util/cloexec.o
> +LIB_OBJS += $(OUTPUT)util/thread-stack.o
>  
>  LIB_OBJS += $(OUTPUT)ui/setup.o
>  LIB_OBJS += $(OUTPUT)ui/helpline.o
> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
> index c89518e..e84f929 100644
> --- a/tools/perf/util/event.h
> +++ b/tools/perf/util/event.h
> @@ -143,6 +143,32 @@ struct branch_stack {
>  	struct branch_entry	entries[0];
>  };
>  
> +enum {
> +	PERF_FLAG_BRANCH		= 1ULL << 0,
> +	PERF_FLAG_CALL			= 1ULL << 1,
> +	PERF_FLAG_RETURN		= 1ULL << 2,
> +	PERF_FLAG_CONDITIONAL		= 1ULL << 3,
> +	PERF_FLAG_SYSCALLRET		= 1ULL << 4,
> +	PERF_FLAG_ASYNC			= 1ULL << 5,
> +	PERF_FLAG_INTERRUPT		= 1ULL << 6,
> +	PERF_FLAG_TX_ABORT		= 1ULL << 7,
> +	PERF_FLAG_TRACE_BEGIN		= 1ULL << 8,
> +	PERF_FLAG_TRACE_END		= 1ULL << 9,
> +	PERF_FLAG_IN_TX			= 1ULL << 10,
> +};
> +
> +#define PERF_BRANCH_MASK	(\
> +	PERF_FLAG_BRANCH	|\
> +	PERF_FLAG_CALL		|\
> +	PERF_FLAG_RETURN	|\
> +	PERF_FLAG_CONDITIONAL	|\
> +	PERF_FLAG_SYSCALLRET	|\
> +	PERF_FLAG_ASYNC		|\
> +	PERF_FLAG_INTERRUPT	|\
> +	PERF_FLAG_TX_ABORT	|\
> +	PERF_FLAG_TRACE_BEGIN	|\
> +	PERF_FLAG_TRACE_END)
> +
>  struct perf_sample {
>  	u64 ip;
>  	u32 pid, tid;
> diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
> new file mode 100644
> index 0000000..c1ca2a9
> --- /dev/null
> +++ b/tools/perf/util/thread-stack.c
> @@ -0,0 +1,151 @@
> +/*
> + * thread-stack.c: Synthesize a thread's stack using call / return events
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#include "thread.h"
> +#include "event.h"
> +#include "util.h"
> +#include "thread-stack.h"
> +
> +#define STACK_GROWTH 4096
> +
> +struct thread_stack_entry {
> +	u64 ret_addr;
> +};
> +
> +struct thread_stack {
> +	struct thread_stack_entry *stack;
> +	size_t cnt;
> +	size_t sz;
> +	u64 trace_nr;
> +};
> +
> +static void thread_stack__grow(struct thread_stack *ts)
> +{
> +	struct thread_stack_entry *new_stack;
> +	size_t sz, new_sz;
> +
> +	new_sz = ts->sz + STACK_GROWTH;
> +	sz = new_sz * sizeof(struct thread_stack_entry);
> +	new_stack = realloc(ts->stack, sz);
> +	if (new_stack) {
> +		ts->stack = new_stack;
> +		ts->sz = new_sz;
> +	}
> +}
> +
> +static struct thread_stack *thread_stack__new(void)
> +{
> +	struct thread_stack *ts;
> +
> +	ts = zalloc(sizeof(struct thread_stack));
> +	if (!ts)
> +		return NULL;
> +
> +	thread_stack__grow(ts);
> +	if (!ts->stack) {
> +		free(ts);
> +		return NULL;
> +	}
> +
> +	return ts;
> +}
> +
> +static void thread_stack__push(struct thread_stack *ts, u64 ret_addr)
> +{
> +	if (ts->cnt == ts->sz) {
> +		thread_stack__grow(ts);
> +		if (ts->cnt == ts->sz)
> +			ts->cnt = 0;
> +	}
> +
> +	ts->stack[ts->cnt++].ret_addr = ret_addr;
> +}

So can you elaborate on the use case, i.e. this silently trows the
existing stack contents away if it doesn't grow, looks strange :-\

Merits some explanation about why this is OK, to say the least.

> +
> +static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
> +{
> +	if (!ts->cnt)
> +		return;
> +
> +	if (ts->stack[ts->cnt - 1].ret_addr == ret_addr) {
> +		ts->cnt -= 1;
> +	} else {
> +		size_t i = ts->cnt - 1;
> +
> +		while (i--) {
> +			if (ts->stack[i].ret_addr == ret_addr) {
> +				ts->cnt = i;
> +				return;
> +			}
> +		}
> +	}
> +}
> +
> +void thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
> +			 u64 to_ip, u16 insn_len, u64 trace_nr)
> +{
> +	if (!thread)
> +		return;
> +
> +	if (!thread->ts) {
> +		thread->ts = thread_stack__new();
> +		if (!thread->ts)
> +			return;
> +		thread->ts->trace_nr = trace_nr;
> +	}
> +
> +	if (trace_nr != thread->ts->trace_nr) {
> +		thread->ts->trace_nr = trace_nr;
> +		thread->ts->cnt = 0;
> +	}
> +
> +	if (flags & PERF_FLAG_CALL) {
> +		u64 ret_addr;
> +
> +		if (!to_ip)
> +			return;
> +		ret_addr = from_ip + insn_len;
> +		if (ret_addr == to_ip)
> +			return; /* Zero-length calls are excluded */
> +		thread_stack__push(thread->ts, ret_addr);
> +	} else if (flags & PERF_FLAG_RETURN) {
> +		if (!from_ip)
> +			return;
> +		thread_stack__pop(thread->ts, to_ip);
> +	}
> +}
> +
> +void thread_stack__free(struct thread *thread)
> +{
> +	if (thread->ts) {
> +		zfree(&thread->ts->stack);
> +		zfree(&thread->ts);
> +	}
> +}
> +
> +void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
> +			  size_t sz, u64 ip)
> +{
> +	size_t i;
> +
> +	if (!thread || !thread->ts)
> +		chain->nr = 1;
> +	else
> +		chain->nr = min(sz, thread->ts->cnt + 1);
> +
> +	chain->ips[0] = ip;
> +
> +	for (i = 1; i < chain->nr; i++)
> +		chain->ips[i] = thread->ts->stack[thread->ts->cnt - i].ret_addr;
> +}
> diff --git a/tools/perf/util/thread-stack.h b/tools/perf/util/thread-stack.h
> new file mode 100644
> index 0000000..c0ba4cf
> --- /dev/null
> +++ b/tools/perf/util/thread-stack.h
> @@ -0,0 +1,32 @@
> +/*
> + * thread-stack.h: Synthesize a thread's stack using call / return events
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#ifndef __PERF_THREAD_STACK_H
> +#define __PERF_THREAD_STACK_H
> +
> +#include <sys/types.h>
> +
> +#include <linux/types.h>
> +
> +struct thread;
> +struct ip_callchain;
> +
> +void thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
> +			 u64 to_ip, u16 insn_len, u64 trace_nr);
> +void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
> +			  size_t sz, u64 ip);
> +void thread_stack__free(struct thread *thread);
> +
> +#endif
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index 2b7b2d9..4e3418d 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -4,6 +4,7 @@
>  #include <string.h>
>  #include "session.h"
>  #include "thread.h"
> +#include "thread-stack.h"
>  #include "util.h"
>  #include "debug.h"
>  #include "comm.h"
> @@ -66,6 +67,8 @@ void thread__delete(struct thread *thread)
>  {
>  	struct comm *comm, *tmp;
>  
> +	thread_stack__free(thread);
> +
>  	if (thread->mg) {
>  		map_groups__put(thread->mg);
>  		thread->mg = NULL;
> diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> index 8c75fa7..a057820 100644
> --- a/tools/perf/util/thread.h
> +++ b/tools/perf/util/thread.h
> @@ -8,6 +8,8 @@
>  #include "symbol.h"
>  #include <strlist.h>
>  
> +struct thread_stack;
> +
>  struct thread {
>  	union {
>  		struct rb_node	 rb_node;
> @@ -25,6 +27,7 @@ struct thread {
>  	int			comm_len;
>  
>  	void			*priv;
> +	struct thread_stack	*ts;
>  };
>  
>  struct machine;
> -- 
> 1.9.1
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