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selftest: size: Add size test for Linux kernel

PATCH Superseded Tim Bird 2 participants 3 messages Nov 27, 2014 – Dec 3, 2014

Subsystems (2)
Kselftest ABI/API

v4 of 6 Superseded Latest is v6 →

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Tim Bird

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PATCH v4 1/1 selftest: size: Add size test for Linux kernel

This test shows the amount of memory used by the system. Note that this is dependent on the user-space that is loaded when this program runs. Optimally, this program would be run as the init program itself.

The program is optimized for size itself, to avoid conflating its own execution with that of the system software.
The code is compiled statically, with no stdlibs. On my x86_64 system, this results in a statically linked binary of less than 5K.

Signed-off-by Tim Bird <tim.bird-/[email protected]>

---
Changes from v3:
- fix copyright string (again!)
- use __builtin_strlen instead of my own strlen
- replace main with _start
- add more human-readable output
- put libgcc reference into a variable in Makefile

Changes from v2:
- add return values to print routines
- add .gitignore file

Changes from v1:
- use more correct Copyright string in get_size.c

 tools/testing/selftests/Makefile        |   1 +
 tools/testing/selftests/size/.gitignore |   1 +
 tools/testing/selftests/size/Makefile   |  23 +++++++
 tools/testing/selftests/size/get_size.c | 111 ++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 tools/testing/selftests/size/.gitignore
 create mode 100644 tools/testing/selftests/size/Makefile
 create mode 100644 tools/testing/selftests/size/get_size.c
tools/testing/selftests/Makefile +1 -0
index 45f145c..fa91aef 100644
@@ -15,6 +15,7 @@ TARGETS += user
 TARGETS += sysctl
 TARGETS += firmware
 TARGETS += ftrace
+TARGETS += size
 
 TARGETS_HOTPLUG = cpu-hotplug
 TARGETS_HOTPLUG += memory-hotplug
tools/testing/selftests/size/.gitignore new file +1 -0
new file mode 100644
index 0000000..189b781
@@ -0,0 +1 @@
+get_size
tools/testing/selftests/size/Makefile new file +23 -0
new file mode 100644
index 0000000..1862786
@@ -0,0 +1,23 @@
+#ifndef CC
+	CC = $(CROSS_COMPILE)gcc
+#endif
+
+#ifndef STRIP
+	STRIP = $(CROSS_COMPILE)strip
+#endif
+
+all: get_size
+
+LIBGCC=$(shell $(CC) -print-libgcc-file-name)
+
+get_size: get_size.c
+	$(CC) --static -ffreestanding -nostartfiles \
+		-Wl,--entry=_start get_size.c $(LIBGCC) \
+		-o get_size
+	$(STRIP) -s get_size
+
+run_tests: all
+	./get_size
+
+clean:
+	$(RM) get_size
tools/testing/selftests/size/get_size.c new file +111 -0

111 lines not on this page · raw message

Signature · 1 line
1.8.2.2
#1 lore raw
Quoted 2 lines · Tim Bird
tools/testing/selftests/size/Makefile new file +0 -0

[...]

tools/testing/selftests/size/Makefile line 16

Quoted 6 lines
tools/testing/selftests/size/Makefile new file +6 -0
+LIBGCC=$(shell $(CC) -print-libgcc-file-name)
+
+get_size: get_size.c
+	$(CC) --static -ffreestanding -nostartfiles \
+		-Wl,--entry=_start get_size.c $(LIBGCC) \
+		-o get_size

You don't need -Wl,--entry=_start; that's the default.

You shouldn't need to manually find libgcc, either; the compiler should do that for you. What goes wrong if you don't include that? If you're trying to link libgcc statically, try -static-libgcc.

Also, static is normally spelled -static, not --static.

Quoted 2 lines
tools/testing/selftests/size/get_size.c new file +0 -0

[...]

Quoted 1 line

+int print(const char *s)

This function, and all the others apart from _start, should be declared static.

Quoted 1 line

+void num_to_str(unsigned long num, char *s)

Likewise, static.

Quoted 7 lines
tools/testing/selftests/size/get_size.c new file +7 -0
+{
+	unsigned long long temp, div;
+	int started;
+
+	temp = num;
+	div = 1000000000000000000LL;
+	started = 0;

tools/testing/selftests/size/get_size.c line 58

Quoted 10 lines
tools/testing/selftests/size/get_size.c new file +10 -0
+	while (div) {
+		if (temp/div || started) {
+			*s++ = (unsigned char)(temp/div + '0');
+			started = 1;
+		}
+		temp -= (temp/div)*div;
+		div /= 10;
+	}
+	*s = 0;
+}

You'd probably end up with significantly smaller code (and no divisions, and thus no corner cases on architectures that need a special function to do unsigned long long division) if you print in hex. You could also drop the "no leading zeros" logic, and just *always* print a 64-bit value as 16 hex digits.

Quoted 1 line

+int print_num(unsigned long num)

Likewise, static.

Quoted 11 lines
tools/testing/selftests/size/get_size.c new file +11 -0
+{
+	char num_buf[30];
+
+	num_to_str(num, num_buf);
+	return print(num_buf);
+}
+
+int print_k_value(const char *s, unsigned long num, unsigned long units)
+{
+	unsigned long long temp;
+	int ccode;

tools/testing/selftests/size/get_size.c line 81

Quoted 10 lines
tools/testing/selftests/size/get_size.c new file +10 -0
+
+	print(s);
+
+	temp = num;
+	temp = (temp * units)/1024;
+	num = temp;
+	ccode = print_num(num);
+	print("\n");
+	return ccode;
+}

I'd suggest dropping this entirely, and just always printing the exact values returned by sysinfo. Drop the multiply, too, and just print info.mem_unit as well. It's easy to post-process the value in a more capable environment.

tools/testing/selftests/size/get_size.c line 95

Quoted 13 lines
tools/testing/selftests/size/get_size.c new file +13 -0
+/* this program has no main(), as startup libraries are not used */
+void _start(void)
+{
+	int ccode;
+	struct sysinfo info;
+	unsigned long used;
+
+	print("Testing system size.\n");
+	print("1..1\n");
+
+	ccode = sysinfo(&info);
+	if (ccode < 0) {
+		print("not ok 1 get size runtime size\n");

Shouldn't the "not ok" here and the "ok" below have the same test description?

Quoted 19 lines
tools/testing/selftests/size/get_size.c new file +16 -0
+		print("# could not get sysinfo\n");
+		_exit(ccode);
+	}
+	/* ignore cache complexities for now */
+	used = info.totalram - info.freeram - info.bufferram;
+	print_k_value("ok 1 get runtime memory use # size = ", used,
+		info.mem_unit);
+
+	print("# System runtime memory report (units in Kilobytes):\n");
+	print_k_value("#   Total:  ", info.totalram, info.mem_unit);
+	print_k_value("#   Free:   ", info.freeram, info.mem_unit);
+	print_k_value("#   Buffer: ", info.bufferram, info.mem_unit);
+	print_k_value("#   In use: ", used, info.mem_unit);
+
+	_exit(0);
+}
Signature · 1 line
1.8.2.2
author
#2 lore raw
Quoted 4 lines · Josh Triplett
Quoted 2 lines · Tim Bird
tools/testing/selftests/size/Makefile new file +0 -0

[...]

Quoted 8 lines

tools/testing/selftests/size/Makefile line 16

Quoted 6 lines
tools/testing/selftests/size/Makefile new file +6 -0
+LIBGCC=$(shell $(CC) -print-libgcc-file-name)
+
+get_size: get_size.c
+	$(CC) --static -ffreestanding -nostartfiles \
+		-Wl,--entry=_start get_size.c $(LIBGCC) \
+		-o get_size

You don't need -Wl,--entry=_start; that's the default.

OK - it works without this. Thanks.

Quoted 5 lines

You shouldn't need to manually find libgcc, either; the compiler should do that for you. What goes wrong if you don't include that? If you're trying to link libgcc statically, try -static-libgcc.

Also, static is normally spelled -static, not --static.

Hmm. Not sure where I got --static from, but it worked. But if -static is the norm I'm fine changing to that.

Upon experimentation, I don't need the explicit libgcc or for that matter the -static-libgcc either.

Quoted 7 lines
Quoted 2 lines
tools/testing/selftests/size/get_size.c new file +0 -0

[...]

Quoted 1 line

+int print(const char *s)

This function, and all the others apart from _start, should be declared static.

OK will do.

Quoted 3 lines
Quoted 1 line

+void num_to_str(unsigned long num, char *s)

Likewise, static.

OK

Quoted 15 lines
Quoted 15 lines
tools/testing/selftests/size/get_size.c new file +15 -0
+{
+	unsigned long long temp, div;
+	int started;
+
+	temp = num;
+	div = 1000000000000000000LL;
+	started = 0;
+	while (div) {
+		if (temp/div || started) {
+			*s++ = (unsigned char)(temp/div + '0');
+			started = 1;
+		}
+		temp -= (temp/div)*div;
+		div /= 10;
+	}
Quoted 8 lines

tools/testing/selftests/size/get_size.c

Quoted 2 lines
tools/testing/selftests/size/get_size.c new file +2 -0
+	*s = 0;
+}

You'd probably end up with significantly smaller code (and no divisions, and thus no corner cases on architectures that need a special function to do unsigned long long division) if you print in hex. You could also drop the "no leading zeros" logic, and just *always* print a 64-bit value as 16 hex digits.

I'd like to keep base-10 output. As far as size is concerned, the code is now at well under 2 pages (8k), which is much smaller than any actually useful program. The only noticeable change in size would be if I got it under 4096, but I don't want to sacrifice too many features to get there (as that's still only 1 page difference in memory usage.)

BTW - using sstrip, I can get it to 4096 already, as is.

Unfortunately, 'sstrip -z', which gets it to 2061, makes it not work. I need to check out what the problem is there. Also, the ELF file still has an unneeded note section. I think easier reductions, without sacrificing functionality, are available by tweaking the ELF header (ie fixing sstrip, for those that want to use it).

Quoted 3 lines
Quoted 1 line

+int print_num(unsigned long num)

Likewise, static.

OK

Quoted 18 lines
Quoted 18 lines
tools/testing/selftests/size/get_size.c new file +18 -0
+{
+	char num_buf[30];
+
+	num_to_str(num, num_buf);
+	return print(num_buf);
+}
+
+int print_k_value(const char *s, unsigned long num, unsigned long units)
+{
+	unsigned long long temp;
+	int ccode;
+
+	print(s);
+
+	temp = num;
+	temp = (temp * units)/1024;
+	num = temp;
+	ccode = print_num(num);
Quoted 8 lines

tools/testing/selftests/size/get_size.c line 81

Quoted 3 lines
tools/testing/selftests/size/get_size.c new file +3 -0
+	print("\n");
+	return ccode;
+}

I'd suggest dropping this entirely, and just always printing the exact values returned by sysinfo. Drop the multiply, too, and just print info.mem_unit as well. It's easy to post-process the value in a more capable environment.

I'd prefer to keep the output easily human-readable.

Quoted 8 lines
Quoted 8 lines
tools/testing/selftests/size/get_size.c new file +8 -0
+/* this program has no main(), as startup libraries are not used */
+void _start(void)
+{
+	int ccode;
+	struct sysinfo info;
+	unsigned long used;
+
+	print("Testing system size.\n");
Quoted 8 lines

tools/testing/selftests/size/get_size.c line 95

Quoted 5 lines
tools/testing/selftests/size/get_size.c new file +5 -0
+	print("1..1\n");
+
+	ccode = sysinfo(&info);
+	if (ccode < 0) {
+		print("not ok 1 get size runtime size\n");

Shouldn't the "not ok" here and the "ok" below have the same test description?

Yes. Thanks. Good catch.

Quoted 10 lines
Quoted 10 lines
tools/testing/selftests/size/get_size.c new file +10 -0
+		print("# could not get sysinfo\n");
+		_exit(ccode);
+	}
+	/* ignore cache complexities for now */
+	used = info.totalram - info.freeram - info.bufferram;
+	print_k_value("ok 1 get runtime memory use # size = ", used,
+		info.mem_unit);
+
+	print("# System runtime memory report (units in Kilobytes):\n");
+	print_k_value("#   Total:  ", info.totalram, info.mem_unit);
Quoted 8 lines
Quoted 8 lines
tools/testing/selftests/size/get_size.c new file +6 -0
+	print_k_value("#   Free:   ", info.freeram, info.mem_unit);
+	print_k_value("#   Buffer: ", info.bufferram, info.mem_unit);
+	print_k_value("#   In use: ", used, info.mem_unit);
+
+	_exit(0);
+}
Signature · 1 line
1.8.2.2

OK - look for a new version shortly (maybe not today, though).
-- Tim