From owner-freebsd-bugs@freebsd.org Thu Aug 31 10:21:10 2017 Return-Path: Delivered-To: freebsd-bugs@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 5EE80E1B431 for ; Thu, 31 Aug 2017 10:21:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4CFBD71F65 for ; Thu, 31 Aug 2017 10:21:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id v7VALAw1046705 for ; Thu, 31 Aug 2017 10:21:10 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 221956] cam iosched: Schedule cam_iosched_ticker() quanta times per second Date: Thu, 31 Aug 2017 10:21:10 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: patch X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: fk@fabiankeil.de X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: mfc-stable11? X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status keywords bug_severity priority component assigned_to reporter flagtypes.name attachments.created Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 31 Aug 2017 10:21:10 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D221956 Bug ID: 221956 Summary: cam iosched: Schedule cam_iosched_ticker() quanta times per second Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Keywords: patch Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: fk@fabiankeil.de Flags: mfc-stable11? Created attachment 185947 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D185947&action= =3Dedit cam iosched: Schedule cam_iosched_ticker() quanta times per second The attached patch lets cam iosched schedule cam_iosched_ticker() quanta times per second According to callout_reset(9), "[w]hen ticks is used, the callout is scheduled to execute after ticks/hz seconds". It follows that to get quanta calls per second one should specify a tick value of hz / isc->quanta. Previously the value was additionally reduced by one. As a result cam_iosched_ticker() was called more often than requested by the user and expected by some of the limiters. On a system with hz=3D1000 a quanta value of 200 resulted in 250 calls and a value of 100 in 111 calls. Without the unexplained tick reduction the number of calls matches the quanta value reasonably well. Obtained from: ElectroBSD --=20 You are receiving this mail because: You are the assignee for the bug.=