Re: [dev] [st] Removing timeouts in main loop

From: Roberto E. Vargas Caballero <k0ga_AT_shike2.com>
Date: Sun, 16 Sep 2012 13:03:13 +0200

> The timeout "problem" was introduced to speed up the rendering when a
> lot of text is printed.
> The logic is basically to not redraw on every read when the throughput is high:

I tried do the same thing putting the draw at the end of the loop, so if you
have a high throughput you will read more characters in ttyread and you will
do more operations that will not be rended.

Maybe a way to improve my patches is testing is some data can be read from
the file descriptors and in this case continue the loop. something like:

int i = 0;
for(;;) {
        FD_ZERO(&rfd);
        FD_SET(cmdfd, &rfd);
        FD_SET(xfd, &rfd);
        if(select(MAX(xfd, cmdfd)+1, &rfd, NULL, NULL, NULL) < 0)
                if(errno == EINTR)
                         continue;
                die("select failed: %s\n", SERRNO);
        }
repeat:
        if(FD_ISSET(cmdfd, &rfd))
                ttyread();

        while(XPending(xw.dpy)) {
              XNextEvent(xw.dpy, &ev);
              if(XFilterEvent(&ev, xw.win))
                      continue;
              if(handler[ev.type])
                     (handler[ev.type])(&ev);
        }
        if(i++ < 4) {
               struct timeval tv = {0};
               FD_ZERO(&rfd);
               FD_SET(cmdfd, &rfd);
               FD_SET(xfd, &rfd);
               if(select(MAX(xfd, cmdfd)+1, &rfd, NULL, NULL, &tv) > 0)
                            goto repeat;
        }
        i = 0;
        draw();
        XFlush(xw.dpy);
}


> I don't have a unix machine at the moment but here is a simple testcase:
>
> $ dd if=/dev/random bs=4K count=100 | hexdump
>
> Increase the count and compare with other terms if necessary.

$ time dd if=/dev/zero bs=4K count=100 | hexdump -C -v

st before patches:

real 0m1.250s
user 0m0.616s
sys 0m0.308s

st after patches:

real 0m1.151s
user 0m0.536s
sys 0m0.296s


xterm:

real 0m4.501s
user 0m0.380s
sys 0m0.156s


uxterm:

real 0m1.384s
user 0m0.492s
sys 0m0.256s
Received on Sun Sep 16 2012 - 13:03:13 CEST