Date: Wed, 22 Sep 2004 17:57:30 EDT From: TM4525@aol.com To: freebsd-questions@freebsd.org Subject: Device polling question - Freebsd 4.9 Message-ID: <67.3411dd28.2e834f4a@aol.com>
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I'm a bit confused about device polling. I put a counter in em_poll(), and then enabled device polling for 10 seconds and read back the counter, and it was called 1.5million times. This is with virtually no network activity and HZ set to the default of 100. The docs seem to imply that the polling function gets called once per clock tick, but that doesn't seem to be the case at all. I'm trying to figure the reasoning behind mucking with the HZ value, which may affect some other things and also seems to defeat the purpose of trying to reduce overhead. With the HZ value at 100 the system easily passes 90K pps, but Im concerned about what variations occur when the system is under load, or if there are time-consuming activities (like extensive firewall rules). Also, when using device polling, even under heavy network load "top" shows the system to be almost completely idle. How can I gauge system usage when using polling instead of interrupts? Its difficult to compare the 2 methods when one of them can't be measured. TIA Tommy Mato
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