Date: Tue, 25 Sep 2007 13:13:47 +0400 From: "Artem Kuchin" <matrix@itlegion.ru> To: "Nikos Vassiliadis" <nvass@teledomenet.gr>, <freebsd-stable@freebsd.org> Subject: Re: device polling and weird timer interrupt count from vmstat Message-ID: <00b801c7ff54$6796f2b0$0c00a8c0@Artem> References: <01ae01c7fd3e$e6ff28f0$0c00a8c0@Artem> <001301c7fed4$7e5f38c0$0c00a8c0@Artem> <200709251048.20808.nvass@teledomenet.gr>
next in thread | previous in thread | raw e-mail | index | archive | help
Nikos Vassiliadis wrote: > On Monday 24 September 2007 20:58, Artem Kuchin wrote: >>> 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? > > <DOUBLING> > I can only make assumptions about the doubling, and I don't want to. > FreeBSD is not a RTOS and some milliseconds variation is > understandable. > >>> 2) if it is supposed to be doubled (why?) when why not 2000? > > I can only make assumptions about the doubling, and I don't want to. > FreeBSD is not a RTOS and some milliseconds variation is > understandable. </DOUBLING> > >>> 3) Is timer int really generated on each cpu? > > Apparently, why do you doubt it? > >>> Am i really wasting cpu >>> time on ~4000 ints per second? > > You can lower it you know, if you feel that you are waisting > that much resources. Ofcourse you'll break your traffic flow > that way, since latency will increase. > > You seem very upset about it, are you sure you want to use > polling(4)? it uses much more resources than interrupts. I am not upset about all this. But i want to understand why is it doubled. Because when i turn on polling i think that timer freq supposed to be just like i set HZ. However, actually, i am now thinking about another issue. I have dual CPU with HT. If i turn on HT (and it does help in my case) it shoud 2000 int x4 = 8000 ints per second. SO, i have saved 200 int/second from NIC and got myself 8000 ints/second from timer. Did i really win anything? I wish there were some good explanation on this. >>> 4) does twe driver use polling? whay about twa? how to check it in >>> the sources? > > Polling is only used on some network interface drivers. Polling(4) > does not offer generic device-polling facilities. > > By the way, you know your post has an aggressive sense, don't you? > Please don't do this when asking questions and want replies. Hmm.. Really? I didn't mean it, i was just trying to me as short and as technical as possible. Alright, i'll give a though on how to be more.. polite, i guess. -- Regards, Artem
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?00b801c7ff54$6796f2b0$0c00a8c0>