lockstat.cc

#include "types.h"
#include "user.h"
#include <fcntl.h>
#include "amd64.h"
#include "uk/lockstat.h"
#include <stdio.h>
#include <unistd.h>

#include <vector>

static void
xwrite(int fd, char c)
{
  if (write(fd, &c, 1) != 1)
    die("lockstat: write failed");
}

static void
stats(void)
{
  static const u64 sz = sizeof(struct lockstat);
  struct lockstat ls;
  int sfd, fd;
  int r;

  fd = open("/dev/lockstat", O_RDONLY);
  if (fd < 0)
    die("lockstat: open failed");

  unlink("/lockstat.last");
  sfd = open("/lockstat.last", O_RDWR|O_CREAT, 0666);
  if (sfd < 0)
    die("lockstat: open failed");

  printf("## name acquires contends locking locked\n");
  dprintf(sfd, "## name acquires contends locking locked\n");
  
  while (1) {
    r = read(fd, &ls, sz);
    if (r < 0)
      die("lockstat: read failed");
    if (r == 0)
      break;
    if (r != sz)
      die("lockstat: unexpected read");

    u64 acquires = 0, contends = 0,
      locking = 0, locked = 0;
    
    for (int i = 0; i < NCPU; i++) {
      acquires += ls.cpu[i].acquires;
      contends += ls.cpu[i].contends;
      locking += ls.cpu[i].locking;
      locked += ls.cpu[i].locked;
    }
    if (contends > 0) {
      printf("%s %lu %lu %lu %lu\n", 
             ls.name, acquires, contends, locking, locked);
      dprintf(sfd, "%s %lu %lu %lu %lu\n",
             ls.name, acquires, contends, locking, locked);
    }
  }

  close(sfd);
}

int
main(int ac, char * const av[])
{
  if (ac <= 1)
    die("usage: %s command...", av[0]);

  int fd = open("/dev/lockstat", O_RDWR);
  if (fd < 0)
    die("lockstat: open failed");
  xwrite(fd, '2');
  xwrite(fd, '3');

  int pid = fork();
  if (pid < 0)
    die("lockstat: fork failed");

  if (pid == 0) {
    xwrite(fd, '1');
    std::vector<const char *> args(av + 1, av + ac);
    args.push_back(nullptr);
    execv(args[0], const_cast<char * const *>(args.data()));
    die("lockstat: exec failed");
  }
  
  wait(NULL);
  xwrite(fd, '2');
  stats();
  xwrite(fd, '3');
  return 0;
}