Solaris 10 上的 Unix 域套接字比 Linux 上慢 100 倍？

Question

我正在为一个项目在 Linux 和 Solaris 上对本地套接字性能进行基准测试。出于某种原因，我不知道，Solaris 上的性能比 Linux 上的性能差大约 100 倍。在 Linux 中，打开一个套接字，每次交换一个非常短（2 个字符）的消息，然后关闭它大约需要 10us 的时间。在 Solaris 上，同样的事情大约需要 1000us。

设置是 Virtual Box 和 Linux 中的 Solaris 10 developer vm，两者都在同一个 Virtual Box 中，并且直接在同一个硬件上（没有区别）。

这是 Solaris 的一个已知问题吗？有什么方法可以解决它？由于无法进入此处的原因，我无法使用本地网络连接。

下面的客户端和服务器代码。使用“cc -fast -m64 -lrt -lsocket -lnsl -o server server.c”和客户端的等效项进行编译。随 Solaris 10 提供的 Gcc 3.4.3 提供了类似的结果。此代码已被删减，例如超时已被删除，结束错误处理最少。

server.c:

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <time.h>
#include <string.h>
#include <unistd.h>

#define DIRECTORY "sub/"
#define FULL_PATH "sub/c_socket"
#define MAX_COMMAND_LEN 8192
#define PERMISSIONS 0700

void on_error(int err, char * msg) {  // simple convenient error handler
  if (err == -1) {                    // Tests whether 'err' is -1 and
    perror(msg);                      // prints error and msg if so.
    exit(-1);
  }
}

int main() {
  struct sockaddr_un addr;
  int srv_fd, inst_fd;
  int inst_adr_size;
  char c;
  int ret;
  char readbuf[MAX_COMMAND_LEN];
  int num_read;
  fd_set rfds;
  int fail;
  int i;

  // make address
  memset(&addr, 0, sizeof(addr));  // clear out addr
  addr.sun_family = AF_UNIX;
  strncpy(addr.sun_path, FULL_PATH, sizeof(addr.sun_path));

  // Remove old pseudo file if present
  ret = unlink(FULL_PATH);
  if (ret == -1 && errno != ENOENT) {
    on_error(ret,"\nRemoving old socket file\n");
  }
  // Remove old directory if present
  ret = rmdir(DIRECTORY);
  if (ret == -1 && errno != ENOENT) {
    on_error(ret, "\nRemoving old socket directory\n");
  }

  // Re-create new directory with appropriate permissonsm
  ret = mkdir(DIRECTORY, PERMISSIONS);
  on_error(ret,"\nCreating directoroy for socket file\n");

  // create server listening socket
  srv_fd = socket(AF_UNIX, SOCK_STREAM, 0);
  on_error(srv_fd, "\nSocket creation:\n");

  // bind server listening socket to address
  ret = bind(srv_fd, (struct sockaddr *) &addr, sizeof(addr));
  on_error(ret, "\nSocket binding:\n");

  // set file permissions for socket file (somewhat redundant)
  ret = chmod(FULL_PATH, PERMISSIONS);
  on_error(ret, "\nSetting socket file permissions\n");

  // set socket listening and queue length
  ret = listen(srv_fd, 10);
  on_error(ret, "\nSet socket to listen:\n");
  while(1) {
    // accept requests
    inst_fd = accept(srv_fd, NULL, NULL);
    on_error(inst_fd, "\n accepting connection:\n");

    // prepare to use select on inst_fd
    FD_ZERO(&rfds);
    FD_SET(inst_fd, &rfds);

    // now interact with the client on the instance socket.
    while(1) {
      num_read = 0;

      while (1) {
        // read a line terminated by '\n'
        ret = select(inst_fd + 1, &rfds, NULL, NULL, NULL);
        on_error(ret, "\nSelect on socket\n");

        if (ret == 1) {
          // we can read something
          ret = recv(inst_fd, readbuf+num_read, MAX_COMMAND_LEN-num_read, 0
          on_error(ret, "\nrecv:\n");

          if (ret == 0) {
            break; // we have EOF
          }

          num_read += ret;
          if (readbuf[num_read - 1] == '\n') {
            break;
          }
        }
      } /* reading one input line done */

      if (num_read == 0) break; // EOF propagated

      // process command: Just send 2 chars back
      ret = send(inst_fd, "n\n", 2, 0);
    }
    close(inst_fd);               // clean up
  }
  // runs forever...
}

client.c:

#include <stdio.h>
#include <time.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define RCVBUFSIZE 8192   /* Size of receive buffer */
#define FULL_PATH "sub/c_socket"
#define CYCLES 100000

void on_error(int err, char * msg) {  // more convenient error output
  if (err == -1) {                    // Tests whether 'err' is -1 and
    perror(msg);                      // prints error and msg if so.
    exit(-1);
  }
}

int main(int argc, char *argv[]) {
  int client_fd;
  struct sockaddr_un addr;
  char readbuf[RCVBUFSIZE+1];
  int num_read;
  int ret;
  int count;
  fd_set rfds;

  char * msg = "N\n";

  // make address
  memset(&addr, 0, sizeof(addr));  // clear out addr
  addr.sun_family = AF_UNIX;
  strncpy(addr.sun_path, FULL_PATH, sizeof(addr.sun_path));

  for(count = 0; count < CYCLES; count++) {
    // create socket
    client_fd = socket(PF_UNIX, SOCK_STREAM, 0);
    on_error(client_fd, "socket() failed");

    // prepare to use select on inst_fd
    FD_ZERO(&rfds);
    FD_SET(client_fd, &rfds);

    // connect
    ret = connect(client_fd, (struct sockaddr *) &addr, sizeof(addr));
    on_error(ret, "connect() failed");

    // send msg to server
    ret = send(client_fd, msg, 2, 0);
    if (ret != 2) {
      on_error(-1, "\nnot all bytes sent\n");
    }

    num_read = 0;
    // read until we have a '\n'
    while (1) {
      ret = select(client_fd + 1, &rfds, NULL, NULL, NULL);
      on_error(ret, "\nSelect on socket\n");

      if (ret == 1) {
        // we can read something
        ret = recv(client_fd, readbuf + num_read, RCVBUFSIZE - num_read, 0)
        on_error(ret, "\nrecv:\n");
        num_read += ret;
        if (readbuf[num_read - 1] == '\n') break;
      }
    }
    if (num_read == 0) break;
    close(client_fd);
  }
  return(0);
}

Answer 1

我在研究套接字并尝试编写 ftp 服务器时遇到了类似的问题：由于转换为 ascii 时出现错误，我最终一次写入一个字节的文件，但在 linux 上没问题，而在 windows 上我最终在循环接口上得到了类似 100KB/s 的速度......如果是这种情况，增加字节数应该会减少差异很多。 似乎在 linux 下请求系统调用的行为更快。

PS 我对操作系统的内部了解不多，所以如果有人可以分享一些指针来理解这个问题（比如http://yarchive.net/comp/linux/linux_speed.html），我将不胜感激。