Re: mod_file_cache performance

[Brian Pane]

dean gaudet wrote:
[...]

>a mostly optimal syscall sequence for responses to a keep-alive
>connection on linux should look something like:
>
>       sockfd = accept();
>       fcntl(sockfd, F_SETFL, O_NDELAY)
>       setsockopt(sockfd, TCP_CORK = 1)
>       while (1) {
>               rc = read(sockfd);
>               if (rc <= 0) {
>                       save_errno = errno;
>                       /* send any remaining packets now */
>                       setsockopt(sockfd, TCP_CORK = 0);
>                       if (rc == 0) break;
>                       if (save_errno == EAGAIN) {
>                               poll(until we can read sockfd);
>                               continue;
>                       }
>                       /* log error */
>                       break;
>               }
>               /* parse request */
>               respfd = open(response_file);
>               write(sockfd, response headers)
>               sendfile(sockfd, respfd)
>               close(respfd)
>       }
>       close(sockfd);
>

The current 2.0 httpd does basically this, except that it resets the
TCP_CORK and TCP_NODELAY flags (to 'off' and 'on,' respectively)
after each sendfile call (rather than just when it gets EAGAIN on a
read).  This seems like a bug.  Is there some context in which the resetting
of these flags after every sendfile call is really necessary?

--Brian