Date: Thu, 9 Oct 2003 17:13:58 -0700 From: Sam Leffler <sam@errno.com> To: "Michael O. Boev" <mike@tric.tomsk.gov.ru>, "Terry Lambert" <tlambert2@mindspring.com> Cc: freebsd-current@freebsd.org Subject: Re: Why is em nic generating interrupts? Message-ID: <200310091713.58815.sam@errno.com> In-Reply-To: <MOEOKMEIFPGOADALOHONEEKACHAA.mike@tric.tomsk.gov.ru> References: <MOEOKMEIFPGOADALOHONEEKACHAA.mike@tric.tomsk.gov.ru>
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On Thursday 09 October 2003 05:57 am, Michael O. Boev wrote: > > -----Original Message----- > > From: Terry Lambert [mailto:tlambert2@mindspring.com] > > Sent: Thursday, October 09, 2003 5:19 PM > > To: Michael O. Boev > > Cc: freebsd-current@FreeBSD.ORG > > Subject: Re: Why is em nic generating interrupts? > > > > "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. > > To this dare I object, that there is traffic going through this machine, > and fxp0 is NOT generating interrupts, while em IS. So, if the rule above > works, they both have to behave in same ways. > > > If all else fails, read the source code... 8-). > > )) I've tried to, but... had to ask here. So all is left is to ask Luigi > and Intel. I cannot comment on 5.1-R, but I am running DEVICE_POLLING tests today with -current and 2 em NICS and systat -vm shows no interrupts for the IRQs where the NICs are. I can only guess that either 5.1-R has a bug or the polling support was not in the driver at that point. Sam
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