Date: Mon, 14 Sep 2009 01:58:39 -0700 (PDT) From: Barney Cordoba <barney_cordoba@yahoo.com> To: Bruce Evans <brde@optusnet.com.au>, rihad <rihad@mail.ru> Cc: freebsd-net@FreeBSD.org Subject: Re: [POLLING] strange interrupt/system load Message-ID: <676338.40771.qm@web63905.mail.re1.yahoo.com> In-Reply-To: <4AADF2D8.5050505@mail.ru>
next in thread | previous in thread | raw e-mail | index | archive | help
--- On Mon, 9/14/09, rihad <rihad@mail.ru> wrote: > From: rihad <rihad@mail.ru> > Subject: Re: [POLLING] strange interrupt/system load > To: "Bruce Evans" <brde@optusnet.com.au> > Cc: freebsd-net@FreeBSD.org > Date: Monday, September 14, 2009, 3:38 AM > Bruce Evans wrote: > > On Sat, 12 Sep 2009, rihad wrote: > > > >> The box experiences ~230 mbit/s traffic flow > through it. I've doubled some sysctls after reading > polling(4): > >> kern.polling.each_burst=10 # was: 5 > >> kern.polling.burst_max=350 # was: 150 > >> > >> FreeBSD 7.2-RELEASE-p3 amd64 > >> HZ=1000 > > > > How much better does it work without POLLING? > > > Without polling (current load around 190-200 mbit/s, around > 24-26 kpps): > > top: > CPU: 0.0% user, 0.0% nice, 8.4% > system, 0.0% interrupt, 91.6% idle > > Interrupts/s: 18322 total > 28 mpt0 irq16 > 1999 cpu0: time > 6906 em0 irq256 > 3392 em1 irq257 > 1999 cpu1: time > 1999 cpu2: time > 1999 cpu3: time You really need to look at the taskq usage as averaging on a 4 core system muddies things up. em will generally run on 1 core per NIC, and interrupts are filtered so you won't see any interrupt usage. On a 4 core system you could exhaust a core and still be at 25% overall, so you need to watch the max usage per core. Things aren't measured properly in polling mode so its difficult to compare them one to one. You really don't need to; intuitively it makes zero sense to use polling with em. You'll do a lot better setting your ITR to 2000 or so. You really don't need an interrupt every 4 packets at those traffic levels. Barney
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?676338.40771.qm>