Date: Thu, 9 Oct 2003 11:04:14 -0400 From: Don Bowman <don@sandvine.com> To: 'Terry Lambert' <tlambert2@mindspring.com>, "Michael O. Boev" <mike@tric.tomsk.gov.ru> Cc: freebsd-current@FreeBSD.ORG Subject: RE: Why is em nic generating interrupts? Message-ID: <FE045D4D9F7AED4CBFF1B3B813C85337035E3A8E@mail.sandvine.com>
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From: Terry Lambert [mailto:tlambert2@mindspring.com] > "Michael O. Boev" wrote: > > I've got a [uniprocessor 5.1-RELEASE] router machine with > fxp and em nics. > > I've built my kernel with the following included: > > > > options DEVICE_POLLING > > options HZ=2500 > > > > and enabled polling in /etc/sysctl.conf. > [ ... ] > > What's happening? Is polling working in my case? > > If yes, why is vmstat showing interrupts? I see clearly, > > that fxp's counter doesn't increase, and em's is constantly growing. > > > > Is there anyone who knows for sure that em's polling works? > > You may want to ask Luigi; polling is his code. > > However, I believe the issue is that polling doesn't start > until you take an interrupt, and it stops as soon as there is > no more data to process, and waits for the next interrupt. > > If you were to jack your load way up, you would probably see > an increase in interrupts, then them dropping off dramatically. > > If all else fails, read the source code... 8-). FWIW, this works for me with 4.7. As terry says, you do see a couple of initial interrupts, as below, and then they stop. $ vmstat -i interrupt total rate em0 irq16 4 0 em1 irq17 4 0 ahc0 irq18 5653 0 ahc1 irq19 15 0 em2 irq20 4 0 mux irq21 3 0 sio0 irq4 1583 0 sio1 irq3 1 0 clk irq0 14545633 2501 rtc irq8 744224 128 Total 15297124 2631
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