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From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org
Cc: Stephane Eranian <eranian@google.com>, Ian Rogers <irogers@google.com>
Subject: [PATCH v3 2/3] lib kallsyms: parse using io api
Date: Tue,  5 May 2020 07:36:24 -0700	[thread overview]
Message-ID: <20200505143625.147832-3-irogers@google.com> (raw)
In-Reply-To: <20200505143625.147832-1-irogers@google.com>

Perf record will call kallsyms__parse 4 times during startup and process
megabytes of data. This changes kallsyms__parse to use the io library
rather than fgets to improve performance of the user code by over 8%.

Before:
  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 103.988 ms (+- 0.203 ms)
After:
  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 95.571 ms (+- 0.006 ms)

For a workload like:
$ perf record /bin/true
Run under 'perf record -e cycles:u -g' the time goes from:
Before
30.10%     1.67%  perf     perf                [.] kallsyms__parse
After
25.55%    20.04%  perf     perf                [.] kallsyms__parse
So a little under 5% of the start-up time is removed. A lot of what
remains is on the kernel side, but caching kallsyms within perf would
at least impact memory footprint.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/lib/api/io.h          |  3 ++
 tools/lib/symbol/kallsyms.c | 81 +++++++++++++++++++------------------
 2 files changed, 45 insertions(+), 39 deletions(-)

diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h
index b7e55b5f8a4a..777c20f6b604 100644
--- a/tools/lib/api/io.h
+++ b/tools/lib/api/io.h
@@ -7,6 +7,9 @@
 #ifndef __API_IO__
 #define __API_IO__
 
+#include <stdlib.h>
+#include <unistd.h>
+
 struct io {
 	/* File descriptor being read/ */
 	int fd;
diff --git a/tools/lib/symbol/kallsyms.c b/tools/lib/symbol/kallsyms.c
index 1a7a9f877095..1f2f519a4e3f 100644
--- a/tools/lib/symbol/kallsyms.c
+++ b/tools/lib/symbol/kallsyms.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "symbol/kallsyms.h"
+#include "api/io.h"
 #include <stdio.h>
-#include <stdlib.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 
 u8 kallsyms2elf_type(char type)
 {
@@ -28,61 +30,62 @@ int hex2u64(const char *ptr, u64 *long_val)
 	return p - ptr;
 }
 
+static void read_to_eol(struct io *io)
+{
+	int ch;
+
+	for (;;) {
+		ch = io__get_char(io);
+		if (ch < 0 || ch == '\n')
+			return;
+	}
+}
+
 int kallsyms__parse(const char *filename, void *arg,
 		    int (*process_symbol)(void *arg, const char *name,
 					  char type, u64 start))
 {
-	char *line = NULL;
-	size_t n;
-	int err = -1;
-	FILE *file = fopen(filename, "r");
+	struct io io;
+	char bf[BUFSIZ];
+	int err;
 
-	if (file == NULL)
-		goto out_failure;
+	io.fd = open(filename, O_RDONLY, 0);
 
-	err = 0;
-
-	while (!feof(file)) {
-		u64 start;
-		int line_len, len;
-		char symbol_type;
-		char *symbol_name;
-
-		line_len = getline(&line, &n, file);
-		if (line_len < 0 || !line)
-			break;
+	if (io.fd < 0)
+		return -1;
 
-		line[--line_len] = '\0'; /* \n */
+	io__init(&io, io.fd, bf, sizeof(bf));
 
-		len = hex2u64(line, &start);
+	err = 0;
+	while (!io.eof) {
+		__u64 start;
+		int ch;
+		size_t i;
+		char symbol_type;
+		char symbol_name[KSYM_NAME_LEN + 1];
 
-		/* Skip the line if we failed to parse the address. */
-		if (!len)
+		if (io__get_hex(&io, &start) != ' ') {
+			read_to_eol(&io);
 			continue;
-
-		len++;
-		if (len + 2 >= line_len)
+		}
+		symbol_type = io__get_char(&io);
+		if (io__get_char(&io) != ' ') {
+			read_to_eol(&io);
 			continue;
-
-		symbol_type = line[len];
-		len += 2;
-		symbol_name = line + len;
-		len = line_len - len;
-
-		if (len >= KSYM_NAME_LEN) {
-			err = -1;
-			break;
 		}
+		for (i = 0; i < sizeof(symbol_name); i++) {
+			ch = io__get_char(&io);
+			if (ch < 0 || ch == '\n')
+				break;
+			symbol_name[i]  = ch;
+		}
+		symbol_name[i]  = '\0';
 
 		err = process_symbol(arg, symbol_name, symbol_type, start);
 		if (err)
 			break;
 	}
 
-	free(line);
-	fclose(file);
+	close(io.fd);
 	return err;
-
-out_failure:
-	return -1;
 }
-- 
2.26.2.526.g744177e7f7-goog


  parent reply	other threads:[~2020-05-05 14:36 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05 14:36 [PATCH v3 0/3] Improvements for kallsyms__parse Ian Rogers
2020-05-05 14:36 ` [PATCH v3 1/3] perf bench: add kallsyms parsing Ian Rogers
2020-05-05 14:36 ` Ian Rogers [this message]
2020-05-05 14:36 ` [PATCH v3 3/3] lib kallsyms: move hex2u64 out of header Ian Rogers

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