diff options
| author | Beau Belgrave <beaub@linux.microsoft.com> | 2022-07-28 16:33:08 -0700 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-09-29 10:17:37 -0400 |
| commit | 39d6d08b2edf99c4b39a689a70bf0adee065b357 (patch) | |
| tree | 2dfb47d9ea7e51415af2cd79815f2c9597786655 /samples | |
| parent | d401b72458562c2f2a81dad162de5c1b8e191e17 (diff) | |
tracing/user_events: Use bits vs bytes for enabled status page data
User processes may require many events and when they do the cache
performance of a byte index status check is less ideal than a bit index.
The previous event limit per-page was 4096, the new limit is 32,768.
This change adds a bitwise index to the user_reg struct. Programs check
that the bit at status_bit has a bit set within the status page(s).
Link: https://lkml.kernel.org/r/20220728233309.1896-6-beaub@linux.microsoft.com
Link: https://lore.kernel.org/all/2059213643.196683.1648499088753.JavaMail.zimbra@efficios.com/
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'samples')
| -rw-r--r-- | samples/user_events/example.c | 25 |
1 files changed, 18 insertions, 7 deletions
diff --git a/samples/user_events/example.c b/samples/user_events/example.c index 4f5778e441c0..d06dc24156ec 100644 --- a/samples/user_events/example.c +++ b/samples/user_events/example.c @@ -12,13 +12,21 @@ #include <fcntl.h> #include <stdio.h> #include <unistd.h> +#include <asm/bitsperlong.h> +#include <endian.h> #include <linux/user_events.h> +#if __BITS_PER_LONG == 64 +#define endian_swap(x) htole64(x) +#else +#define endian_swap(x) htole32(x) +#endif + /* Assumes debugfs is mounted */ const char *data_file = "/sys/kernel/debug/tracing/user_events_data"; const char *status_file = "/sys/kernel/debug/tracing/user_events_status"; -static int event_status(char **status) +static int event_status(long **status) { int fd = open(status_file, O_RDONLY); @@ -33,7 +41,8 @@ static int event_status(char **status) return 0; } -static int event_reg(int fd, const char *command, int *status, int *write) +static int event_reg(int fd, const char *command, long *index, long *mask, + int *write) { struct user_reg reg = {0}; @@ -43,7 +52,8 @@ static int event_reg(int fd, const char *command, int *status, int *write) if (ioctl(fd, DIAG_IOCSREG, ®) == -1) return -1; - *status = reg.status_index; + *index = reg.status_bit / __BITS_PER_LONG; + *mask = endian_swap(1L << (reg.status_bit % __BITS_PER_LONG)); *write = reg.write_index; return 0; @@ -51,8 +61,9 @@ static int event_reg(int fd, const char *command, int *status, int *write) int main(int argc, char **argv) { - int data_fd, status, write; - char *status_page; + int data_fd, write; + long index, mask; + long *status_page; struct iovec io[2]; __u32 count = 0; @@ -61,7 +72,7 @@ int main(int argc, char **argv) data_fd = open(data_file, O_RDWR); - if (event_reg(data_fd, "test u32 count", &status, &write) == -1) + if (event_reg(data_fd, "test u32 count", &index, &mask, &write) == -1) return errno; /* Setup iovec */ @@ -75,7 +86,7 @@ ask: getchar(); /* Check if anyone is listening */ - if (status_page[status]) { + if (status_page[index] & mask) { /* Yep, trace out our data */ writev(data_fd, (const struct iovec *)io, 2); |