Device Polling code for -current.

Non-SMP, i386-only, no polling in the idle loop at the moment.

To use this code you must compile a kernel with

        options DEVICE_POLLING

and at runtime enable polling with

        sysctl kern.polling.enable=1

The percentage of CPU reserved to userland can be set with

        sysctl kern.polling.user_frac=NN (default is 50)

while the remainder is used by polling device drivers and netisr's.
These are the only two variables that you should need to touch. There
are a few more parameters in kern.polling but the default values
are adequate for all purposes. See the code in kern_poll.c for
more details on them.

Polling in the idle loop will be implemented shortly by introducing
a kernel thread which does the job. Until then, the amount of CPU
dedicated to polling will never exceed (100-user_frac).
The equivalent (actually, better) code for -stable is at

	http://info.iet.unipi.it/~luigi/polling/

and also supports polling in the idle loop.

NOTE to Alpha developers:
There is really nothing in this code that is i386-specific.
If you move the 2 lines supporting the new option from
sys/conf/{files,options}.i386 to sys/conf/{files,options} I am
pretty sure that this should work on the Alpha as well, just that
I do not have a suitable test box to try it. If someone feels like
trying it, I would appreciate it.

NOTE to other developers:
sure some things could be done better, and as always I am open to
constructive criticism, which a few of you have already given and
I greatly appreciated.
However, before proposing radical architectural changes, please
take some time to possibly try out this code, or at the very least
read the comments in kern_poll.c, especially re. the reason why I
am using a soft netisr and cannot (I believe) replace it with a
simple timeout.

Quick description of files touched by this commit:

sys/conf/files.i386
        new file kern/kern_poll.c
sys/conf/options.i386
        new option
sys/i386/i386/trap.c
        poll in trap (disabled by default)
sys/kern/kern_clock.c
        initialization and hardclock hooks.
sys/kern/kern_intr.c
        minor swi_net changes
sys/kern/kern_poll.c
        the bulk of the code.
sys/net/if.h
        new flag
sys/net/if_var.h
        declaration for functions used in device drivers.
sys/net/netisr.h
        NETISR_POLL
sys/dev/fxp/if_fxp.c
sys/dev/fxp/if_fxpvar.h
sys/pci/if_dc.c
sys/pci/if_dcreg.h
sys/pci/if_sis.c
sys/pci/if_sisreg.h
        device driver modifications

1 files changed, 12 insertions, 0 deletions

diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 4c2ccc0..a338dca 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -69,6 +69,12 @@
 #include <sys/gmon.h>
 #endif
 
+#ifdef DEVICE_POLLING
+#include <net/netisr.h>		/* for NETISR_POLL */
+ 
+extern void ether_poll1(void);
+extern void hardclock_device_poll(void);
+#endif /* DEVICE_POLLING */
 
 static void initclocks __P((void *dummy));
 SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL)
@@ -140,6 +146,9 @@ initclocks(dummy)
 	psdiv = pscnt = 1;
 	cpu_initclocks();
 
+#ifdef DEVICE_POLLING
+	register_netisr(NETISR_POLL, ether_poll1);
+#endif
 	/*
 	 * Compute profhz/stathz, and fix profhz if needed.
 	 */
@@ -212,6 +221,9 @@ hardclock(frame)
 		statclock(frame);
 
 	tc_windup();
+#ifdef DEVICE_POLLING
+	hardclock_device_poll();
+#endif /* DEVICE_POLLING */
 
 	/*
 	 * Process callouts at a very low cpu priority, so we don't keep the