mirror of
https://github.com/torvalds/linux.git
synced 2025-11-04 02:30:34 +02:00
39d6d08b2e
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>
102 lines
2 KiB
C
102 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Copyright (c) 2021, Microsoft Corporation.
|
|
*
|
|
* Authors:
|
|
* Beau Belgrave <beaub@linux.microsoft.com>
|
|
*/
|
|
|
|
#include <errno.h>
|
|
#include <sys/ioctl.h>
|
|
#include <sys/mman.h>
|
|
#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(long **status)
|
|
{
|
|
int fd = open(status_file, O_RDONLY);
|
|
|
|
*status = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ,
|
|
MAP_SHARED, fd, 0);
|
|
|
|
close(fd);
|
|
|
|
if (*status == MAP_FAILED)
|
|
return -1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int event_reg(int fd, const char *command, long *index, long *mask,
|
|
int *write)
|
|
{
|
|
struct user_reg reg = {0};
|
|
|
|
reg.size = sizeof(reg);
|
|
reg.name_args = (__u64)command;
|
|
|
|
if (ioctl(fd, DIAG_IOCSREG, ®) == -1)
|
|
return -1;
|
|
|
|
*index = reg.status_bit / __BITS_PER_LONG;
|
|
*mask = endian_swap(1L << (reg.status_bit % __BITS_PER_LONG));
|
|
*write = reg.write_index;
|
|
|
|
return 0;
|
|
}
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
int data_fd, write;
|
|
long index, mask;
|
|
long *status_page;
|
|
struct iovec io[2];
|
|
__u32 count = 0;
|
|
|
|
if (event_status(&status_page) == -1)
|
|
return errno;
|
|
|
|
data_fd = open(data_file, O_RDWR);
|
|
|
|
if (event_reg(data_fd, "test u32 count", &index, &mask, &write) == -1)
|
|
return errno;
|
|
|
|
/* Setup iovec */
|
|
io[0].iov_base = &write;
|
|
io[0].iov_len = sizeof(write);
|
|
io[1].iov_base = &count;
|
|
io[1].iov_len = sizeof(count);
|
|
|
|
ask:
|
|
printf("Press enter to check status...\n");
|
|
getchar();
|
|
|
|
/* Check if anyone is listening */
|
|
if (status_page[index] & mask) {
|
|
/* Yep, trace out our data */
|
|
writev(data_fd, (const struct iovec *)io, 2);
|
|
|
|
/* Increase the count */
|
|
count++;
|
|
|
|
printf("Something was attached, wrote data\n");
|
|
}
|
|
|
|
goto ask;
|
|
|
|
return 0;
|
|
}
|