From owner-freebsd-net@freebsd.org Mon Nov 9 01:32:39 2015 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BBB9FA242F2 for ; Mon, 9 Nov 2015 01:32:39 +0000 (UTC) (envelope-from ralsaadi@swin.edu.au) Received: from iport2.cc.swin.edu.au (iport2.cc.swin.edu.au [136.186.0.52]) by mx1.freebsd.org (Postfix) with ESMTP id 4BC3B14AA for ; Mon, 9 Nov 2015 01:32:38 +0000 (UTC) (envelope-from ralsaadi@swin.edu.au) X-IronPort-AV: E=Sophos;i="5.20,264,1444654800"; d="scan'208";a="14534697" Received: from gsp-ex01.ds.swin.edu.au (HELO outlook.swin.edu.au) ([136.186.126.17]) by iport2.cc.swin.edu.au with ESMTP; 09 Nov 2015 12:31:23 +1100 Received: from GSP-EX02.ds.swin.edu.au ([169.254.2.2]) by gsp-ex01.ds.swin.edu.au ([169.254.1.85]) with mapi id 14.03.0248.002; Mon, 9 Nov 2015 12:31:22 +1100 From: Rasool Al-Saadi To: Bruce Evans , Hans Petter Selasky CC: "freebsd-net@freebsd.org" Subject: RE: Timing issue with Dummynet on high kernel timer interrupt Thread-Topic: Timing issue with Dummynet on high kernel timer interrupt Thread-Index: AdEWOVE5DoAlkzqPQWaBZ8ln4esVd///TXiA//0UVtCABdKzgP/+Z6XggAMXeACAAAG5AIAAEWQAgAAEeACAAFKsAP/+mCjAAEzugIAACVnfAAACPDQA//zRgBA= Date: Mon, 9 Nov 2015 01:31:22 +0000 Message-ID: <6545444AE21C2749939E637E56594CEA3C0E4D6B@gsp-ex02.ds.swin.edu.au> References: <6545444AE21C2749939E637E56594CEA3C0DCCC4@gsp-ex02.ds.swin.edu.au> <5638B7B5.3030802@selasky.org> <6545444AE21C2749939E637E56594CEA3C0DE7FF@gsp-ex02.ds.swin.edu.au> <563B2703.5080402@selasky.org> <6545444AE21C2749939E637E56594CEA3C0E0BD9@gsp-ex02.ds.swin.edu.au> <563C6864.2090907@selasky.org> <563C786C.1050305@selasky.org> <563CC186.9000807@selasky.org> <6545444AE21C2749939E637E56594CEA3C0E1B79@gsp-ex02.ds.swin.edu.au> <20151107162915.A893@besplex.bde.org> <563DD6B2.8010607@selasky.org> <20151107223816.D1837@besplex.bde.org> In-Reply-To: <20151107223816.D1837@besplex.bde.org> Accept-Language: en-AU, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [136.186.126.11] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Nov 2015 01:32:39 -0000 On Saturday, 7 November 2015 10:51 PM, Bruce Evans wrote: > On Sat, 7 Nov 2015, Hans Petter Selasky wrote: >=20 > > On 11/07/15 07:19, Bruce Evans wrote: > >> I don't know if CTLFLAG_RWTUN with SYSCTL_PROC() actually works for > >> all types, but it is used with CTLFLAG_STRING for kern.corefile. > >> This is another bogus undocumented tunable. It is better documented > >> as a sysctl than most since it is old so it is documented in > >> sysctl(8). It is not documented as a tunable there of course. It is > >> also not documented as a tunable in core(5). > > > > SYSCTL_PROC() works with RWTUN from /boot/loader.conf, as long as the > > procedure callback handles early calls during boot. >=20 > Hmm, that would be messy if it wants to do hardware stuff like > sysctl_kern_eventtimer_periodic() does. >=20 > Timercounters only have 1 MI tunable > (sysctl_kern_timecounter_adjprecision). It has a (cold) check to avoid d= oing > too much. >=20 > Bruce Thanks a lot all for your help! The results now reasonable when kern.eventtimer.periodic=3D1. sysctl kern.t= imecounter.alloweddeviation=3D0 does not make deference (at least in my tes= t) . Here is RTT vs Time graph when Hz=3D10000, kern.eventtimer.periodic=3D1 and= kern.timecounter.alloweddeviation=3D{default (5), 0} https://goo.gl/photos= /ukxTvpBDeoFCFEPH8 The time deference graph https://goo.gl/photos/AAV8oECBpdvowgsY7 =20 So, what the effects of using periodic mode on the system in general? Why t= he timing issue disappears when eventtimer.periodic=3D0 and C_DIRECT_EXEC = is removed from callout_reset_sbt() call? Cheers, Rasool