Hello!
I've read that *BSD like systems support device polling:
------------------------------------------------------------
You can enable DEVICE_POLLING in your kernel. DEVICE_POLLING changes
the method through which data gets from your network card to the
kernel. Traditionally, each time the network card needs attention (for
example when it receives a packet), it generates an interrupt request.
The request causes a context switch and a call to an interrupt
handler. A context switch is when the CPU and kernel have to switch
from user land (the user's programs or daemons), and kernel land
(dealing with device drivers, hardware, and other kernel-bound tasks).
The last few years have seen significant improvements in the
efficiency of context switching but it is still an extremely expensive
operation. Furthermore, the amount of time the system can have to
spend when dealing with an interrupt can be almost limitless. It is
completely possible for an interrupt to never free the kernel, leaving
your machine unresponsive. Those of us unfortunate enough to be on the
wrong side of certain Denial of Service attacks will know about this.
The DEVICE_POLLING option changes this behavior. It causes the kernel
to poll the network card itself at certain predefined times: at
defined intervals, during idle loops, or on clock interrupts. This
allows the kernel to decide when it is most efficient to poll a device
for updates and for how long, and ultimately results in a significant
increase in performance.
If you want to take advantage of DEVICE_POLLING, you need to compile
two options in to your kernel:
* options DEVICE_POLLING
* options HZ=1000
The first line enables DEVICE_POLLING and the second device slows the
clock interrupts to 1000 times per second. The need to apply the
second, because in the worst case your network card will be polled on
clock ticks. If the clock ticks very fast, you would spend a lot of
time polling devices which defeats the purpose here.
Finally we need to change one sysctl to actually enable this feature.
You can either enable polling at runtime or at boot. If you want to
enable it at boot, add this line to the end of your /etc/sysctl.conf:
* kern.polling.enable=1
The DEVICE_POLLING option by default does not work with SMP enabled
kernels. When the author of the DEVICE_POLLING code initially commited
it he admits he was unsure of the benefits of the feature in a
multiple-CPU environment, as only one CPU would be doing the polling.
Since that time many administrators have found that there is a
significant advantage to DEVICE_POLLING even in SMP enabled kernels
and that it works with no problems at all. If you are compiling an SMP
kernel with DEVICE_POLLING, edit the file:
/usr/src/sys/kern/kern_poll.c and remove the following lines:
#ifdef SMP
#include "opt_lint.h"
#ifndef COMPILING_LINT
#error DEVICE_POLLING is not compatible with SMP
#endif
#endif
---------------------------------------------------------------------------
So, are there any feature like that in linux kernel supported?
P.S. http://silverwraith.com/papers/freebsd-tuning.php
--
Best regards,
kasp mailto:[email protected]
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