* 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
* 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
>
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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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