Message-Id: <20170417225520.28082-2-alexis.berlemont@gmail.com>
Date:   Tue, 18 Apr 2017 00:55:18 +0200
From:   Alexis Berlemont <alexis.berlemont@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Alexis Berlemont <alexis.berlemont@...il.com>,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com
Subject: [PATCH 1/3] perf annotate: implement per-callchain annotation histogram

A symbol can be called from various points and according to its calling
context, it can provide different results.

This patch creates one histogram for every different callchain recorded
and accumulates profiling samples into the appropriate one. Samples
recorded with the same callchain are not mixed with other ones, The
noise should be reduced.

Signed-off-by: Alexis Berlemont <alexis.berlemont@...il.com>
---
 tools/perf/util/annotate.c | 308 ++++++++++++++++++++++++++++++++++++++++++++-
 tools/perf/util/annotate.h |  19 +++
 2 files changed, 324 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 30498a2d4a6f..fa7691a0f205 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -18,6 +18,7 @@
 #include "annotate.h"
 #include "evsel.h"
 #include "block-range.h"
+#include "callchain.h"
 #include "arch/common.h"
 #include <regex.h>
 #include <pthread.h>
@@ -554,7 +555,7 @@ int symbol__alloc_hist(struct symbol *sym)
 {
 	struct annotation *notes = symbol__annotation(sym);
 	const size_t size = symbol__size(sym);
-	size_t sizeof_sym_hist;
+	size_t sizeof_sym_hist, nr_sym_hist;
 
 	/* Check for overflow when calculating sizeof_sym_hist */
 	if (size > (SIZE_MAX - sizeof(struct sym_hist)) / sizeof(u64))
@@ -567,12 +568,17 @@ int symbol__alloc_hist(struct symbol *sym)
 				/ symbol_conf.nr_events)
 		return -1;
 
-	notes->src = zalloc(sizeof(*notes->src) + symbol_conf.nr_events * sizeof_sym_hist);
+	/* Allocate 1 histogram per event and 1 more for context annotation */
+	nr_sym_hist = symbol_conf.nr_events + 1;
+
+	notes->src = zalloc(sizeof(*notes->src) +
+			    nr_sym_hist * sizeof_sym_hist);
 	if (notes->src == NULL)
 		return -1;
 	notes->src->sizeof_sym_hist = sizeof_sym_hist;
-	notes->src->nr_histograms   = symbol_conf.nr_events;
+	notes->src->nr_histograms   = nr_sym_hist;
 	INIT_LIST_HEAD(&notes->src->source);
+	INIT_LIST_HEAD(&notes->src->context_hists);
 	return 0;
 }
 
@@ -591,11 +597,18 @@ static int symbol__alloc_hist_cycles(struct symbol *sym)
 void symbol__annotate_zero_histograms(struct symbol *sym)
 {
 	struct annotation *notes = symbol__annotation(sym);
+	struct cxt_hist_entry *hist_entry;
 
 	pthread_mutex_lock(&notes->lock);
 	if (notes->src != NULL) {
 		memset(notes->src->histograms, 0,
 		       notes->src->nr_histograms * notes->src->sizeof_sym_hist);
+
+		list_for_each_entry(hist_entry,
+				    &notes->src->context_hists, list) {
+			list_del(&hist_entry->list);
+			free(hist_entry);
+		}
 		if (notes->src->cycles_hist)
 			memset(notes->src->cycles_hist, 0,
 				symbol__size(sym) * sizeof(struct cyc_hist));
@@ -681,6 +694,7 @@ static struct annotation *symbol__get_annotation(struct symbol *sym, bool cycles
 		if (symbol__alloc_hist_cycles(sym) < 0)
 			return NULL;
 	}
+
 	return notes;
 }
 
@@ -697,6 +711,281 @@ static int symbol__inc_addr_samples(struct symbol *sym, struct map *map,
 	return __symbol__inc_addr_samples(sym, map, notes, evidx, addr);
 }
 
+static bool __symbol_cxt__cmp_call_cursor(struct cxt_hist_entry *hist_entry,
+					  struct callchain_cursor *cursor)
+{
+	struct callchain_cursor_node *node;
+	struct call_list_entry *entry;
+	u64 match_count = 0;
+
+	callchain_cursor_commit(cursor);
+
+	/*
+	 * One element of the callchain cursor cannot be matched: the last
+	 * element (or first according to the order) which corresponds to the
+	 * real sampled address; so, let's skip it (if need be) and...
+	 */
+	if (callchain_param.order == ORDER_CALLEE)
+		callchain_cursor_advance(cursor);
+
+	/* ...consider it has matched */
+	match_count++;
+
+	list_for_each_entry(entry, &hist_entry->callchain, list) {
+
+		node = callchain_cursor_current(cursor);
+		if (node == NULL)
+			break;
+
+		if (entry->ip == node->ip)
+			match_count++;
+
+		callchain_cursor_advance(cursor);
+	}
+
+	return match_count == cursor->nr;
+}
+
+static int __symbol_cxt__copy_call_cursor(struct cxt_hist_entry *hist_entry,
+					  struct callchain_cursor *cursor)
+{
+	struct callchain_cursor_node *node;
+	struct call_list_entry *entry, *n;
+
+	callchain_cursor_commit(cursor);
+	node = callchain_cursor_current(cursor);
+
+	/*
+	 * For each entry in the callchain cursor, we need to copy 2 fields: the
+	 * text addresses and the symbol in which the address is located...
+	 */
+	while (node) {
+		entry = zalloc(sizeof(*entry));
+		if (entry == NULL)
+			goto error;
+
+		/* ...each address composes a unique key for the callchain ...*/
+		entry->ip = node->ip;
+
+		/* ... the symbol is only useful because the hist_entry's sorted
+		 * callchain does not provide all the addresses.
+		 */
+		entry->sym_start =
+			(node->sym != NULL) ? node->sym->start : node->ip;
+
+		list_add_tail(&entry->list, &hist_entry->callchain);
+
+		callchain_cursor_advance(cursor);
+		node = callchain_cursor_current(cursor);
+	}
+
+	/*
+	 * One element of the callchain cursor should not be copied: the last
+	 * element (or first according to the order) which corresponds to the
+	 * real sampled address; so, let's deleted it from the linked list.
+	 */
+	if (!list_empty(&hist_entry->callchain)) {
+		entry = (callchain_param.order == ORDER_CALLEE) ?
+			list_first_entry(&hist_entry->callchain,
+					 struct call_list_entry, list) :
+			list_last_entry(&hist_entry->callchain,
+					struct call_list_entry, list);
+		list_del(&entry->list);
+		free(entry);
+	}
+
+	return 0;
+
+error:
+
+	list_for_each_entry_safe(entry, n, &hist_entry->callchain, list) {
+		list_del(&entry->list);
+		free(entry);
+	}
+
+	return -ENOMEM;
+}
+
+static struct sym_hist *__symbol_cxt__get_hists(struct annotation *notes,
+						int evidx,
+						struct callchain_cursor *cursor)
+{
+	struct cxt_hist_entry *hist_entry;
+	size_t sizeof_hists;
+
+	/*
+	 * Try to find a contextual histogram (an instance with the same
+	 * callchain)...
+	 */
+	list_for_each_entry(hist_entry, &notes->src->context_hists, list) {
+		if (__symbol_cxt__cmp_call_cursor(hist_entry, cursor))
+			goto return_selection;
+	}
+
+	/* ...if none was found, let's create a new one... */
+	sizeof_hists = notes->src->sizeof_sym_hist * notes->src->nr_histograms;
+	hist_entry = zalloc(sizeof(*hist_entry) + sizeof_hists);
+	if (hist_entry == NULL)
+		return NULL;
+
+	/* ...and copy the callchain from the callchain cursor */
+	INIT_LIST_HEAD(&hist_entry->callchain);
+	if (__symbol_cxt__copy_call_cursor(hist_entry, cursor) < 0) {
+		free(hist_entry);
+		return NULL;
+	}
+
+	list_add(&hist_entry->list, &notes->src->context_hists);
+
+return_selection:
+
+	return (((void *)&hist_entry->histograms) +
+		(notes->src->sizeof_sym_hist * evidx));
+}
+
+static int __symbol_cxt__inc_addr_samples(struct symbol *sym,
+					  struct map *map,
+					  struct annotation *notes,
+					  int evidx, u64 addr,
+					  struct callchain_cursor *cursor)
+{
+	unsigned long offset;
+	struct sym_hist *h;
+
+	pr_debug3("%s: addr=%#" PRIx64 "\n",
+		  __func__, map->unmap_ip(map, addr));
+
+	if ((addr < sym->start || addr >= sym->end) &&
+	    (addr != sym->end || sym->start != sym->end)) {
+		pr_debug("%s(%d): ERANGE! sym->name=%s, start=%#" PRIx64
+			 ", addr=%#" PRIx64 ", end=%#" PRIx64 "\n",
+			 __func__, __LINE__,
+			 sym->name, sym->start, addr, sym->end);
+		return -ERANGE;
+	}
+
+	offset = addr - sym->start;
+	h = __symbol_cxt__get_hists(notes, evidx, cursor);
+	h->sum++;
+	h->addr[offset]++;
+
+	pr_debug3("%#" PRIx64 " %s: period++ [addr: %#" PRIx64 ", %#" PRIx64
+		  ", evidx=%d] => %" PRIu64 "\n", sym->start, sym->name,
+		  addr, addr - sym->start, evidx, h->addr[offset]);
+	return 0;
+}
+
+static int symbol_cxt__inc_addr_samples(struct symbol *sym, struct map *map,
+					int evidx, u64 addr,
+					struct callchain_cursor *cursor)
+{
+	struct annotation *notes;
+
+	if (sym == NULL)
+		return 0;
+	notes = symbol__get_annotation(sym, false);
+	if (notes == NULL)
+		return -ENOMEM;
+	return __symbol_cxt__inc_addr_samples(sym, map, notes,
+					      evidx, addr, cursor);
+}
+
+static bool  __symbol_cxt__cmp_callchain(struct list_head *left_callchain,
+					 struct list_head *right_callchain)
+{
+	struct call_list_entry *left_entry, *right_entry;
+	u64 total_count = 0, match_count = 0;
+
+	right_entry =
+		list_first_entry_or_null(right_callchain,
+					 struct call_list_entry, list);
+
+	/*
+	 * This function compares two callchains (of contextual histograms); so,
+	 * we need to simultaneously go through both callchains and compare
+	 * their entries against each other.
+	 */
+	list_for_each_entry(left_entry, left_callchain, list) {
+
+		if (total_count != match_count)
+			break;
+
+		total_count++;
+
+		if (right_entry == NULL)
+			continue;
+
+		/*
+		 * The right callchain was generated by scanning the elements in
+		 * hist_entry->sorted_chain (used for results display); in case
+		 * of fork, the hold ip address is not correct; so, we have to
+		 * check symbol start addresses.
+		 */
+		if (left_entry->ip == right_entry->ip)
+			match_count++;
+		else if (left_entry->sym_start == right_entry->sym_start)
+			match_count++;
+
+		if (list_is_last(&right_entry->list, right_callchain))
+			right_entry = NULL;
+		else
+			right_entry = list_next_entry(right_entry, list);
+	}
+
+	/*
+	 * We consider that 2 empty callchains are not equal (just because the
+	 * right callchain cannot be empty; this point might/must be flawed.
+	 */
+	return total_count > 0 &&
+		right_entry == NULL && match_count == total_count;
+}
+
+int symbol_cxt__copy_hist(struct symbol *sym, int evidx,
+			  struct list_head *ref_callchain)
+{
+	struct annotation *notes;
+	struct cxt_hist_entry *hist_entry;
+	struct sym_hist *src_hist, *dst_hist;
+	int last_hist_idx;
+
+	/*
+	 * Each per-symbol annotation structure contains per-callchain
+	 * histograms...
+	 */
+	notes = symbol__get_annotation(sym, false);
+	if (notes == NULL)
+		return -ENOENT;
+
+	/*
+	 * ...we need to find the histogram which corresponds to the reference
+	 * callchain passed as argument...
+	 */
+	list_for_each_entry(hist_entry, &notes->src->context_hists, list) {
+
+		if (__symbol_cxt__cmp_callchain(&hist_entry->callchain,
+						ref_callchain)) {
+			goto copy_selection;
+		}
+	}
+
+	return -ENOENT;
+
+copy_selection:
+
+	last_hist_idx = notes->src->nr_histograms - 1;
+
+	/*
+	 * ...and copy it so that it will be displayed as annotation of the
+	 * disassembled symbol code.
+	 */
+	dst_hist = annotation__histogram(notes, last_hist_idx);
+	src_hist = (((void *)&hist_entry->histograms) +
+		    (notes->src->sizeof_sym_hist * evidx));
+	memcpy(dst_hist, src_hist, notes->src->sizeof_sym_hist);
+
+	return 0;
+}
+
 static int symbol__account_cycles(u64 addr, u64 start,
 				  struct symbol *sym, unsigned cycles)
 {
@@ -768,6 +1057,19 @@ int hist_entry__inc_addr_samples(struct hist_entry *he, int evidx, u64 ip)
 	return symbol__inc_addr_samples(he->ms.sym, he->ms.map, evidx, ip);
 }
 
+int hist_entry_cxt__inc_addr_samples(struct hist_entry *he, int evidx, u64 ip,
+				     struct callchain_cursor *cursor)
+{
+	/* Unlike hist_entry_inc_addr_samples which updates a per-symbol
+	 * histogram for code annotation display, this function works with many
+	 * per-symbol histograms: one for every different callchain recorded.
+	 * The interest is to have different annotations according to the
+	 * callchain context.
+	 */
+	return symbol_cxt__inc_addr_samples(he->ms.sym,
+					    he->ms.map, evidx, ip, cursor);
+}
+
 static void disasm_line__init_ins(struct disasm_line *dl, struct arch *arch, struct map *map)
 {
 	dl->ins.ops = ins__find(arch, dl->ins.name);
diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
index 948aa8e6fd39..1abad7e32ce3 100644
--- a/tools/perf/util/annotate.h
+++ b/tools/perf/util/annotate.h
@@ -84,6 +84,18 @@ struct sym_hist {
 	u64		addr[0];
 };
 
+struct call_list_entry {
+	u64    ip;
+	u64    sym_start;
+	struct list_head list;
+};
+
+struct cxt_hist_entry {
+	struct list_head list;
+	struct list_head callchain;
+	struct sym_hist histograms[0];
+};
+
 struct cyc_hist {
 	u64	start;
 	u64	cycles;
@@ -127,6 +139,7 @@ struct annotated_source {
 	int    		   nr_histograms;
 	size_t		   sizeof_sym_hist;
 	struct cyc_hist	   *cycles_hist;
+	struct list_head   context_hists;
 	struct sym_hist	   histograms[0];
 };
 
@@ -155,9 +168,15 @@ int addr_map_symbol__account_cycles(struct addr_map_symbol *ams,
 
 int hist_entry__inc_addr_samples(struct hist_entry *he, int evidx, u64 addr);
 
+int hist_entry_cxt__inc_addr_samples(struct hist_entry *he, int evidx, u64 ip,
+				     struct callchain_cursor *cursor);
+
 int symbol__alloc_hist(struct symbol *sym);
 void symbol__annotate_zero_histograms(struct symbol *sym);
 
+int symbol_cxt__copy_hist(struct symbol *sym,
+			  int evidx, struct list_head *callchain);
+
 int symbol__disassemble(struct symbol *sym, struct map *map, const char *arch_name, size_t privsize);
 
 enum symbol_disassemble_errno {
-- 
2.12.2

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