Date: Mon, 24 Sep 2007 21:58:18 +0400 From: "Artem Kuchin" <matrix@itlegion.ru> To: <freebsd-stable@freebsd.org> Subject: device polling and weird timer interrupt count from vmstat Message-ID: <001301c7fed4$7e5f38c0$0c00a8c0@Artem> References: <01ae01c7fd3e$e6ff28f0$0c00a8c0@Artem>
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Anyone any clue on this issue: Artem Kuchin wrote: > I enabled device polling in the kernel, in nics and > set HZ=1000. > > How, when i do > > omni2# vmstat -i > > i see > > interrupt total rate > irq14: ata0 47 0 > irq15: ata1 41 0 > irq28: em0 2268 4 > irq72: twe0 58380 120 > cpu0: timer 965994 1995 > cpu3: timer 1 0 > cpu1: timer 1 0 > cpu2: timer 965857 1995 > Total 1992589 4116 > > > (it is dual xeon with HT, HT disabled, that why cpu3 and cpu1 are > zero). > > What i don't understand is why timer rate on each cpu is 1995? I have > set it to 1000, not 1995 or 2000. I have seen it showing 2000 on > another box. > So > 1) why not 1000? > 2) if it is supposed to be doubled (why?) when why not 2000? > 3) Is timer int really generated on each cpu? Am i really wasting cpu > time on ~4000 ints per second? > 4) does twe driver use polling? whay about twa? how to check it in > the sources?
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