From owner-freebsd-bugs@freebsd.org Mon Nov 27 17:51:02 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 6F009DBAC59 for ; Mon, 27 Nov 2017 17:51:02 +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 5596C7D52F for ; Mon, 27 Nov 2017 17:51:02 +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 vARHp2l2001943 for ; Mon, 27 Nov 2017 17:51:02 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 223914] [PATCH] Fix bug in which the long term ULE load balancer is executed only once Date: Mon, 27 Nov 2017 17:51:02 +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 Many People X-Bugzilla-Who: justinien.bouron@epfl.ch X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status keywords bug_severity priority component assigned_to reporter 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: 2.1.25 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Nov 2017 17:51:02 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D223914 Bug ID: 223914 Summary: [PATCH] Fix bug in which the long term ULE load balancer is executed only once Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Keywords: patch Severity: Affects Many People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: justinien.bouron@epfl.ch Keywords: patch Created attachment 188323 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D188323&action= =3Dedit Patch for the ULE load balancer solving the issue of this bug report. The load balancer of ULE has a bug which cause it to be executed only once = at startup, and it will *never* be executed again. The reason is simple, when the sched_balance function is called for the fir= st time, the smp is not yet setup, and the function returns. However the balance_tick variable is not resetted before the return and thus will remains 0 for ever. Because the condition in sched_clock to trigger the load balancer is : " balance_ticks && --balance_ticks =3D=3D 0 ", once balance_ticks is 0, this condition will never be met, and thus the load balancer will never be execu= ted again. To convince yourself you can even put a panic right before the call to sched_balance_group in sched_balance, it will never panic ... The fix is rather simple, just move the line resetting the balance_ticks va= lue *before* the if branch "if (smp_started =3D=3D 0 || rebalance =3D=3D 0)". T= hat way we are sure that the load balancer is re-scheduled. --=20 You are receiving this mail because: You are the assignee for the bug.=