Re: [PATCH v2 bpf-next 1/2] bpf: add a new API libbpf_num_possible

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* Re: [PATCH v2 bpf-next 1/2] bpf: add a new API libbpf_num_possible_cpus()
       [not found] ` <20190606165837.2042247-2-hechaol@fb.com>
@ 2019-06-06 17:14   ` Martin Lau
  0 siblings, 0 replies; 3+ messages in thread
From: Martin Lau @ 2019-06-06 17:14 UTC (permalink / raw)
  To: Hechao Li; +Cc: bpf, netdev, Kernel Team

On Thu, Jun 06, 2019 at 09:58:36AM -0700, Hechao Li wrote:
> Adding a new API libbpf_num_possible_cpus() that helps user with
> per-CPU map operations.
> 
> Signed-off-by: Hechao Li <hechaol@fb.com>
> ---
>  tools/lib/bpf/libbpf.c   | 53 ++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   | 16 ++++++++++++
>  tools/lib/bpf/libbpf.map |  1 +
>  3 files changed, 70 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ba89d9727137..ea80ba6f7dfd 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -3827,3 +3827,56 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
>  					     desc->array_offset, addr);
>  	}
>  }
> +
> +int libbpf_num_possible_cpus(void)
> +{
> +	static const char *fcpu = "/sys/devices/system/cpu/possible";
> +	int len = 0, n = 0, il = 0, ir = 0;
> +	unsigned int start = 0, end = 0;
> +	static int cpus;
> +	char buf[128];
> +	int error = 0;
> +	int fd = -1;
> +
> +	if (cpus > 0)
> +		return cpus;
> +
> +	fd = open(fcpu, O_RDONLY);
> +	if (fd < 0) {
> +		error = errno;
> +		pr_warning("Failed to open file %s: %s\n",
> +			   fcpu, strerror(error));
> +		return -error;
> +	}
> +	len = read(fd, buf, sizeof(buf));
> +	close(fd);
> +	if (len <= 0) {
> +		error = errno;
What is the errno when len == 0?

> +		pr_warning("Failed to read # of possible cpus from %s: %s\n",
> +			   fcpu, strerror(error));
> +		return -error;
> +	}
> +	if (len == sizeof(buf)) {
> +		pr_warning("File %s size overflow\n", fcpu);
> +		return -EOVERFLOW;
> +	}
> +	buf[len] = '\0';
> +
> +	for (ir = 0, cpus = 0; ir <= len; ir++) {
> +		/* Each sub string separated by ',' has format \d+-\d+ or \d+ */
> +		if (buf[ir] == ',' || buf[ir] == '\0') {
> +			buf[ir] = '\0';
> +			n = sscanf(&buf[il], "%u-%u", &start, &end);
> +			if (n <= 0) {
> +				pr_warning("Failed to get # CPUs from %s\n",
> +					   &buf[il]);
> +				return -EINVAL;
> +			} else if (n == 1) {
> +				end = start;
> +			}
> +			cpus += end - start + 1;
> +			il = ir + 1;
> +		}
> +	}
> +	return cpus;
> +}
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 1af0d48178c8..f5e82eb2e5d4 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -454,6 +454,22 @@ bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);
>  LIBBPF_API void
>  bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);
>  
> +/*
> + * A helper function to get the number of possible CPUs before looking up
> + * per-CPU maps. Negative errno is returned on failure.
> + *
> + * Example usage:
> + *
> + *     int ncpus = libbpf_num_possible_cpus();
> + *     if (ncpus <= 0) {
> + *          // error handling
> + *     }
> + *     long values[ncpus];
> + *     bpf_map_lookup_elem(per_cpu_map_fd, key, values);
> + *
> + */
> +LIBBPF_API int libbpf_num_possible_cpus(void);
> +
>  #ifdef __cplusplus
>  } /* extern "C" */
>  #endif
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 46dcda89df21..2c6d835620d2 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -172,4 +172,5 @@ LIBBPF_0.0.4 {
>  		btf_dump__new;
>  		btf__parse_elf;
>  		bpf_object__load_xattr;
> +		libbpf_num_possible_cpus;
>  } LIBBPF_0.0.3;
> -- 
> 2.17.1
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

[parent not found: <20190606165837.2042247-3-hechaol@fb.com>]

* Re: [PATCH v2 bpf-next 2/2] bpf: use libbpf_num_possible_cpus in bpftool and selftests
       [not found] ` <20190606165837.2042247-3-hechaol@fb.com>
@ 2019-06-06 17:17   ` Martin Lau
  2019-06-06 17:17   ` Song Liu
  1 sibling, 0 replies; 3+ messages in thread
From: Martin Lau @ 2019-06-06 17:17 UTC (permalink / raw)
  To: Hechao Li; +Cc: bpf, netdev, Kernel Team

On Thu, Jun 06, 2019 at 09:58:37AM -0700, Hechao Li wrote:
> Use the newly added bpf_num_possible_cpus() in bpftool and selftests
> and remove duplicate implementations.
> 
> Signed-off-by: Hechao Li <hechaol@fb.com>
> ---
>  tools/bpf/bpftool/common.c             | 53 +++-----------------------
>  tools/testing/selftests/bpf/bpf_util.h | 37 +++---------------
>  2 files changed, 10 insertions(+), 80 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
> index f7261fad45c1..0b1c56758cd9 100644
> --- a/tools/bpf/bpftool/common.c
> +++ b/tools/bpf/bpftool/common.c
> @@ -21,6 +21,7 @@
>  #include <sys/vfs.h>
>  
>  #include <bpf.h>
> +#include <libbpf.h> /* libbpf_num_possible_cpus */
>  
>  #include "main.h"
>  
> @@ -439,57 +440,13 @@ unsigned int get_page_size(void)
>  
>  unsigned int get_possible_cpus(void)
>  {
> -	static unsigned int result;
> -	char buf[128];
> -	long int n;
> -	char *ptr;
> -	int fd;
> -
> -	if (result)
> -		return result;
> -
> -	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
> -	if (fd < 0) {
> -		p_err("can't open sysfs possible cpus");
> -		exit(-1);
> -	}
> -
> -	n = read(fd, buf, sizeof(buf));
> -	if (n < 2) {
> -		p_err("can't read sysfs possible cpus");
> -		exit(-1);
> -	}
> -	close(fd);
> +	int cpus = libbpf_num_possible_cpus();
>  
> -	if (n == sizeof(buf)) {
> -		p_err("read sysfs possible cpus overflow");
> +	if (cpus <= 0) {
> +		p_err("can't get # of possible cpus");
>  		exit(-1);
>  	}
> -
> -	ptr = buf;
> -	n = 0;
> -	while (*ptr && *ptr != '\n') {
> -		unsigned int a, b;
> -
> -		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {
> -			n += b - a + 1;
> -
> -			ptr = strchr(ptr, '-') + 1;
> -		} else if (sscanf(ptr, "%u", &a) == 1) {
> -			n++;
> -		} else {
> -			assert(0);
> -		}
> -
> -		while (isdigit(*ptr))
> -			ptr++;
> -		if (*ptr == ',')
> -			ptr++;
> -	}
> -
> -	result = n;
> -
> -	return result;
> +	return cpus;
>  }
>  
>  static char *
> diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
> index a29206ebbd13..9ad9c7595f93 100644
> --- a/tools/testing/selftests/bpf/bpf_util.h
> +++ b/tools/testing/selftests/bpf/bpf_util.h
> @@ -6,44 +6,17 @@
>  #include <stdlib.h>
>  #include <string.h>
>  #include <errno.h>
> +#include <libbpf.h>
>  
>  static inline unsigned int bpf_num_possible_cpus(void)
>  {
> -	static const char *fcpu = "/sys/devices/system/cpu/possible";
> -	unsigned int start, end, possible_cpus = 0;
> -	char buff[128];
> -	FILE *fp;
> -	int len, n, i, j = 0;
> +	int possible_cpus = libbpf_num_possible_cpus();
>  
> -	fp = fopen(fcpu, "r");
> -	if (!fp) {
> -		printf("Failed to open %s: '%s'!\n", fcpu, strerror(errno));
> +	if (possible_cpus <= 0) {
hmmm... so it seems that possible_cpus could be 0?
or libbpf_num_possible_cpus() should never return 0?

> +		printf("Failed to get # of possible cpus: '%s'!\n",
> +		       strerror(-possible_cpus));
strerror(0) does not seem right.

>  		exit(1);
>  	}
> -
> -	if (!fgets(buff, sizeof(buff), fp)) {
> -		printf("Failed to read %s!\n", fcpu);
> -		exit(1);
> -	}
> -
> -	len = strlen(buff);
> -	for (i = 0; i <= len; i++) {
> -		if (buff[i] == ',' || buff[i] == '\0') {
> -			buff[i] = '\0';
> -			n = sscanf(&buff[j], "%u-%u", &start, &end);
> -			if (n <= 0) {
> -				printf("Failed to retrieve # possible CPUs!\n");
> -				exit(1);
> -			} else if (n == 1) {
> -				end = start;
> -			}
> -			possible_cpus += end - start + 1;
> -			j = i + 1;
> -		}
> -	}
> -
> -	fclose(fp);
> -
>  	return possible_cpus;
>  }
>  
> -- 
> 2.17.1
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2 bpf-next 2/2] bpf: use libbpf_num_possible_cpus in bpftool and selftests
       [not found] ` <20190606165837.2042247-3-hechaol@fb.com>
  2019-06-06 17:17   ` [PATCH v2 bpf-next 2/2] bpf: use libbpf_num_possible_cpus in bpftool and selftests Martin Lau
@ 2019-06-06 17:17   ` Song Liu
  1 sibling, 0 replies; 3+ messages in thread
From: Song Liu @ 2019-06-06 17:17 UTC (permalink / raw)
  To: Hechao Li; +Cc: bpf, netdev, Kernel Team



> On Jun 6, 2019, at 9:58 AM, Hechao Li <hechaol@fb.com> wrote:
> 
> Use the newly added bpf_num_possible_cpus() in bpftool and selftests
> and remove duplicate implementations.
> 
> Signed-off-by: Hechao Li <hechaol@fb.com>
> ---
> tools/bpf/bpftool/common.c             | 53 +++-----------------------
> tools/testing/selftests/bpf/bpf_util.h | 37 +++---------------
> 2 files changed, 10 insertions(+), 80 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
> index f7261fad45c1..0b1c56758cd9 100644
> --- a/tools/bpf/bpftool/common.c
> +++ b/tools/bpf/bpftool/common.c
> @@ -21,6 +21,7 @@
> #include <sys/vfs.h>
> 
> #include <bpf.h>
> +#include <libbpf.h> /* libbpf_num_possible_cpus */
> 
> #include "main.h"
> 
> @@ -439,57 +440,13 @@ unsigned int get_page_size(void)
> 
> unsigned int get_possible_cpus(void)
> {
> -	static unsigned int result;
> -	char buf[128];
> -	long int n;
> -	char *ptr;
> -	int fd;
> -
> -	if (result)
> -		return result;
> -
> -	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
> -	if (fd < 0) {
> -		p_err("can't open sysfs possible cpus");
> -		exit(-1);
> -	}
> -
> -	n = read(fd, buf, sizeof(buf));
> -	if (n < 2) {
> -		p_err("can't read sysfs possible cpus");
> -		exit(-1);
> -	}
> -	close(fd);
> +	int cpus = libbpf_num_possible_cpus();
> 
> -	if (n == sizeof(buf)) {
> -		p_err("read sysfs possible cpus overflow");
> +	if (cpus <= 0) {
> +		p_err("can't get # of possible cpus");
> 		exit(-1);
> 	}
> -
> -	ptr = buf;
> -	n = 0;
> -	while (*ptr && *ptr != '\n') {
> -		unsigned int a, b;
> -
> -		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {
> -			n += b - a + 1;
> -
> -			ptr = strchr(ptr, '-') + 1;
> -		} else if (sscanf(ptr, "%u", &a) == 1) {
> -			n++;
> -		} else {
> -			assert(0);
> -		}
> -
> -		while (isdigit(*ptr))
> -			ptr++;
> -		if (*ptr == ',')
> -			ptr++;
> -	}
> -
> -	result = n;
> -
> -	return result;
> +	return cpus;
> }
> 
> static char *
> diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
> index a29206ebbd13..9ad9c7595f93 100644
> --- a/tools/testing/selftests/bpf/bpf_util.h
> +++ b/tools/testing/selftests/bpf/bpf_util.h
> @@ -6,44 +6,17 @@
> #include <stdlib.h>
> #include <string.h>
> #include <errno.h>
> +#include <libbpf.h>
> 
> static inline unsigned int bpf_num_possible_cpus(void)
> {
> -	static const char *fcpu = "/sys/devices/system/cpu/possible";
> -	unsigned int start, end, possible_cpus = 0;
> -	char buff[128];
> -	FILE *fp;
> -	int len, n, i, j = 0;
> +	int possible_cpus = libbpf_num_possible_cpus();
> 
> -	fp = fopen(fcpu, "r");
> -	if (!fp) {
> -		printf("Failed to open %s: '%s'!\n", fcpu, strerror(errno));
> +	if (possible_cpus <= 0) {
> +		printf("Failed to get # of possible cpus: '%s'!\n",
> +		       strerror(-possible_cpus));

strerror(0) is "Success". This is a little weird. 

Thanks,
Song

> 		exit(1);
> 	}
> -
> -	if (!fgets(buff, sizeof(buff), fp)) {
> -		printf("Failed to read %s!\n", fcpu);
> -		exit(1);
> -	}
> -
> -	len = strlen(buff);
> -	for (i = 0; i <= len; i++) {
> -		if (buff[i] == ',' || buff[i] == '\0') {
> -			buff[i] = '\0';
> -			n = sscanf(&buff[j], "%u-%u", &start, &end);
> -			if (n <= 0) {
> -				printf("Failed to retrieve # possible CPUs!\n");
> -				exit(1);
> -			} else if (n == 1) {
> -				end = start;
> -			}
> -			possible_cpus += end - start + 1;
> -			j = i + 1;
> -		}
> -	}
> -
> -	fclose(fp);
> -
> 	return possible_cpus;
> }
> 
> -- 
> 2.17.1
> 


^ permalink raw reply	[flat|nested] 3+ messages in thread

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     [not found] <20190606165837.2042247-1-hechaol@fb.com>
     [not found] ` <20190606165837.2042247-2-hechaol@fb.com>
2019-06-06 17:14   ` [PATCH v2 bpf-next 1/2] bpf: add a new API libbpf_num_possible_cpus() Martin Lau
     [not found] ` <20190606165837.2042247-3-hechaol@fb.com>
2019-06-06 17:17   ` [PATCH v2 bpf-next 2/2] bpf: use libbpf_num_possible_cpus in bpftool and selftests Martin Lau
2019-06-06 17:17   ` Song Liu

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