Date:	Tue, 25 Nov 2014 15:33:37 -0800
From:	Tim Bird <tim.bird@...ymobile.com>
To:	Shuah Khan <shuahkh@....samsung.com>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-embedded@...r.kernel.org" <linux-embedded@...r.kernel.org>,
	Josh Triplett <josh@...htriplett.org>
Subject: Re: [PATCH v3] selftest: size: Add size test for Linux kernel



On 11/25/2014 12:39 PM, Shuah Khan wrote:
> On 11/24/2014 11:20 AM, Tim Bird wrote:
>>
>> 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.
>>
> 
> This following version information shouldn't be part of changelog.
> 
>> Changes from v2:
>>   - add return values to print routines
>>   - add .gitignore file
>>
>> Changes from v1:
>>   - use more correct Copyright string in get_size.c
>>
>> Signed-off-by: Tim Bird <tim.bird@...ymobile.com>
>> ---
> 
> Goes here.

OK - I'll change this.

> 
>>  tools/testing/selftests/Makefile        |   1 +
>>  tools/testing/selftests/size/.gitignore |   1 +
>>  tools/testing/selftests/size/Makefile   |  21 +++++++
>>  tools/testing/selftests/size/get_size.c | 105 ++++++++++++++++++++++++++++++++
>>  4 files changed, 128 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
>>
>> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
>> index 45f145c..fa91aef 100644
>> --- a/tools/testing/selftests/Makefile
>> +++ b/tools/testing/selftests/Makefile
>> @@ -15,6 +15,7 @@ TARGETS += user
>>  TARGETS += sysctl
>>  TARGETS += firmware
>>  TARGETS += ftrace
>> +TARGETS += size
>>  
>>  TARGETS_HOTPLUG = cpu-hotplug
>>  TARGETS_HOTPLUG += memory-hotplug
>> diff --git a/tools/testing/selftests/size/.gitignore b/tools/testing/selftests/size/.gitignore
>> new file mode 100644
>> index 0000000..189b781
>> --- /dev/null
>> +++ b/tools/testing/selftests/size/.gitignore
>> @@ -0,0 +1 @@
>> +get_size
>> diff --git a/tools/testing/selftests/size/Makefile b/tools/testing/selftests/size/Makefile
>> new file mode 100644
>> index 0000000..51e5fbd
>> --- /dev/null
>> +++ b/tools/testing/selftests/size/Makefile
>> @@ -0,0 +1,21 @@
>> +#ifndef CC
>> +	CC = $(CROSS_COMPILE)gcc
>> +#endif
>> +
>> +#ifndef STRIP
>> +	STRIP = $(CROSS_COMPILE)strip
>> +#endif
>> +
>> +all: get_size
>> +
>> +get_size: get_size.c
>> +	$(CC) --static -ffreestanding -nostartfiles \
>> +		-Wl,--entry=main get_size.c -o get_size \
>> +		`cc -print-libgcc-file-name`
>> +	$(STRIP) -s get_size
>> +
>> +run_tests: all
>> +	./get_size
>> +
>> +clean:
>> +	$(RM) get_size
>> diff --git a/tools/testing/selftests/size/get_size.c b/tools/testing/selftests/size/get_size.c
>> new file mode 100644
>> index 0000000..9c8d3cd
>> --- /dev/null
>> +++ b/tools/testing/selftests/size/get_size.c
>> @@ -0,0 +1,105 @@
>> +/*
>> + * Copyright 2014 Sony
>> + *
>> + * Licensed under the terms of the GNU GPL License version 2
>> + *
>> + * Selftest for runtime system size
>> + *
>> + * Prints the amount of RAM that the currently running system is using.
>> + *
>> + * This program tries to be as small as possible itself, to
>> + * avoid perturbing the system memory utilization with its
>> + * own execution.  It also attempts to have as few dependencies
>> + * on kernel features as possible.
>> + *
>> + * It should be statically linked, with startup libs avoided.
>> + * It uses no library calls, and only the following 3 syscalls:
>> + *   sysinfo(), write(), and _exit()
>> + *
>> + * For output, it avoids printf (which in some C libraries
>> + * has large external dependencies) by implementing its own
>> + * strlen(), number output and print() routines.
>> + */
>> +
>> +#include <sys/sysinfo.h>
>> +#include <unistd.h>
>> +
>> +#define STDOUT_FILENO 1
>> +
>> +int my_strlen(const char *s)
>> +{
>> +	int len = 0;
>> +
>> +	while (*s++)
>> +		len++;
>> +	return len;
>> +}
>> +
>> +/*
>> + * num_to_str - put digits from num into *s, left to right
>> + *   do this by dividing the number by powers of 10
>> + *   the tricky part is to omit leading zeros
>> + *   don't print zeros until we've started printing any numbers at all
>> + */
>> +void num_to_str(unsigned long num, char *s)
>> +{
>> +	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;
>> +	}
>> +	*s = 0;
>> +}
>> +
>> +int print_num(unsigned long num)
>> +{
>> +	char num_buf[30];
>> +
>> +	num_to_str(num, num_buf);
>> +	return write(STDOUT_FILENO, num_buf, my_strlen(num_buf));
>> +}
>> +
>> +int print(char *s)
>> +{
>> +	return write(STDOUT_FILENO, s, my_strlen(s));
>> +}
>> +
>> +void main(int argc, char **argv)
>> +{
>> +	int ccode;
>> +	unsigned long used;
>> +	struct sysinfo info;
>> +	unsigned long long temp;
>> +
>> +	print("Testing system size.\n");
>> +	print("1..1\n");
> 
> I ran this test and the reporting could be improved.
> Could you change the above to say
> 
> System RAM in use instead of system size.
I'll have to think about this.  I'm not sure what the
correct phrasing would be for XIP systems (for which part of
the kernel resides in flash, not RAM, maybe "memory"?)

> Also can you also
> print total RAM and other information you already have:
> 
I can print it as part of total output, but for regression
testing and automation I want the tool to have a single
number result as output (well, one number relating to runtime
size, and I'm considering adding one number relating
to compile-time size.)

> Maybe something along the lines of:
> 
> System RAM report (units Kilobytes):
>    Total:
>    Free:
>    Bufferram:
>    In use:
> 
> I would remove the print("1..1\n");

This is part of the TAP output format.

Is there any (other) output format being standardized for selftest
programs?

TAP allows me to output more human-readable information to go
along with the "official" result, but I'd like to keep the
official result in TAP format so it can be handled by automated
tools.  Maybe it would be best to output both.

I'll try to make a counter-proposal tomorrow that we can discus.

>> +
>> +	ccode = sysinfo(&info);
>> +	if (ccode < 0) {
>> +		print("not ok 1 get size runtime size\n");
>> +		print("# could not get sysinfo\n");
>> +		_exit(ccode);
>> +	}
>> +
>> +	/* ignore cache complexities for now */
>> +	temp = info.totalram - info.freeram - info.bufferram;
>> +	temp = temp * info.mem_unit;
>> +	temp = temp / 1024;
>> +
>> +	used = temp;
>> +
>> +	print("ok 1 get runtime size # size = ");
>> +	print_num(used);
>> +	print(" K\n");
> 
> Please see above. You can get rid of print(" K\n"); at the end.
> 
> Sorry for not giving this feedback earlier. The not so clear
> reporting aspect stood out for me after running the test.

No problem.  Thanks for looking at it.
I have some additional changes, based on feedback from Josh Triplett,
so look for a v4 tomorrow.

 -- Tim
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