From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric B Munson Subject: Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host Date: Wed, 14 Dec 2011 12:58:44 -0500 Message-ID: <20111214175844.GD4075@mgebm.net> References: <1323116344-17911-1-git-send-email-emunson@mgebm.net> <4EDF7B0D.4060001@redhat.com> <20111208151929.GA6301@mgebm.net> <4EE8BBF4.8070108@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="DiL7RhKs8rK9YGuF" Return-path: Content-Disposition: inline In-Reply-To: <4EE8BBF4.8070108@redhat.com> Sender: kvm-owner@vger.kernel.org To: Avi Kivity Cc: mingo@redhat.com, hpa@zytor.com, arnd@arndb.de, ryanh@linux.vnet.ibm.com, aliguori@us.ibm.com, mtosatti@redhat.com, jeremy.fitzhardinge@citrix.com, levinsasha928@gmail.com, Jan Kiszka , kvm@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org List-Id: linux-arch.vger.kernel.org --DiL7RhKs8rK9YGuF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, 14 Dec 2011, Avi Kivity wrote: > On 12/08/2011 05:19 PM, Eric B Munson wrote: > > > error compiling committee.c: too many arguments to function > > >=20 > > My concern for preempt notifiers is masking real soft lockup warnings. = If the > > flag is set every time the vm is preempted, it becomes more likely that= we will > > mask real warnings. The ioctl was choosen because it sets the flag onl= y when > > the guest is being paused deliberately. > > > > AFAIK, SIGSTOP is not a supported way to stop a qemu vm so a soft lockup >=20 > This is a kvm patch, not a qemu patch. In general we try to address > general requirements, not just those that are specific to one userspace, > even if it is near to our hearts. >=20 > > warning would be working as designed there. If that isn't the case, or= if it > > ever changes, we could always install a signal handler for SIGCONT that= set the > > flag before resuming the vm. > > > > Scheduling delays are also beyond the scope of this problem and I see t= he soft > > lockup warning as appropriate in that case. >=20 > I don't think you should see a guest softlockup if the host is > overloaded. Nor should you see it due to a long live migration pause, > or STOP/CONT. You should see a guest softlockup if it is spinning due > to a guest bug, and not for any other reason. >=20 > I think we need a mix of the ioctl (for STOP/CONT and voluntary pauses, > like live migration or qemu stop/cont) and preempt notifiers (together > with a check for TASK_RUNNING/TASK_UNINTERRUPTIBLE, for scheduling or > swap delays) >=20 > --=20 > error compiling committee.c: too many arguments to function >=20 Do you want the preemption notifier work in before you will consider merging this set, or can that be a follow on? Eric --DiL7RhKs8rK9YGuF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBAgAGBQJO6OPUAAoJEKhG9nGc1bpJfh0P/27rntQ0sjv9E711ZQm01dhK 7K+sev5s2I0VtZHgNICjQ31D8Ct0PSSOhwvmrs3Fe8SMb+WU18B/NWN8NCX3AFN8 EjRL8846AGfrzAqdKZyezCbEq+q4gDoESst8bH2kXWiKfpeRu7v/K+trALpheS/B HM0B5pJ25hqqy6c18e2mX873WK0gvX2ZnRvitgChnnTGyC29yDh26Xc74mYC5iqP RJ2QYVb99Qc0L7E6263NHoaZOKsGntUNcCBE3H8g487ZEwGaGXL37Cc2+tszAo1x iu38AdVJwMvNlMlIXykHKA2bxhPSIYB4huooCTCy9oRApxV73Sn/N6IVFjN1loHi frDrI5LRHWiSE1lwYQhH5h6C5RGnBIRljjpOqAa5P4lrwbkuf6UV2zJj00m3M+Qz ynk216/CeHQfVtXHurHUK5i2L7D3K9DzM/DogaNCqwbd1jGHAIhaIiRtTzoMeqm0 MgdzqonV0xY6+Xe2MVAJpKL/gitnqIV1We7OAp0BjquQHM3nvNoyhPSrPwR1LEng gNbgQJ32qCPs4ydzS76KJRum7BUi0ai8dE7vu0EdBnUrrPBignEjt8v1EZinmjCl KHlQC7RW6VBjyre7mfOdPHPBCTw+gQ/4nq+u5qA4NqiEmLKmXaiEQ6MqqhTBFJDK gvFdAUa4KV6IToBMkm2T =FWT7 -----END PGP SIGNATURE----- --DiL7RhKs8rK9YGuF-- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from oz.csail.mit.edu ([128.30.30.239]:40786 "EHLO mail.mgebm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756258Ab1LNR6q (ORCPT ); Wed, 14 Dec 2011 12:58:46 -0500 Date: Wed, 14 Dec 2011 12:58:44 -0500 From: Eric B Munson Subject: Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host Message-ID: <20111214175844.GD4075@mgebm.net> References: <1323116344-17911-1-git-send-email-emunson@mgebm.net> <4EDF7B0D.4060001@redhat.com> <20111208151929.GA6301@mgebm.net> <4EE8BBF4.8070108@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="DiL7RhKs8rK9YGuF" Content-Disposition: inline In-Reply-To: <4EE8BBF4.8070108@redhat.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Avi Kivity Cc: mingo@redhat.com, hpa@zytor.com, arnd@arndb.de, ryanh@linux.vnet.ibm.com, aliguori@us.ibm.com, mtosatti@redhat.com, jeremy.fitzhardinge@citrix.com, levinsasha928@gmail.com, Jan Kiszka , kvm@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Message-ID: <20111214175844.o14I-nYuEvx-Lnt3g8xhkwd_cetRyO5VrjcugyBC8hY@z> --DiL7RhKs8rK9YGuF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, 14 Dec 2011, Avi Kivity wrote: > On 12/08/2011 05:19 PM, Eric B Munson wrote: > > > error compiling committee.c: too many arguments to function > > >=20 > > My concern for preempt notifiers is masking real soft lockup warnings. = If the > > flag is set every time the vm is preempted, it becomes more likely that= we will > > mask real warnings. The ioctl was choosen because it sets the flag onl= y when > > the guest is being paused deliberately. > > > > AFAIK, SIGSTOP is not a supported way to stop a qemu vm so a soft lockup >=20 > This is a kvm patch, not a qemu patch. In general we try to address > general requirements, not just those that are specific to one userspace, > even if it is near to our hearts. >=20 > > warning would be working as designed there. If that isn't the case, or= if it > > ever changes, we could always install a signal handler for SIGCONT that= set the > > flag before resuming the vm. > > > > Scheduling delays are also beyond the scope of this problem and I see t= he soft > > lockup warning as appropriate in that case. >=20 > I don't think you should see a guest softlockup if the host is > overloaded. Nor should you see it due to a long live migration pause, > or STOP/CONT. You should see a guest softlockup if it is spinning due > to a guest bug, and not for any other reason. >=20 > I think we need a mix of the ioctl (for STOP/CONT and voluntary pauses, > like live migration or qemu stop/cont) and preempt notifiers (together > with a check for TASK_RUNNING/TASK_UNINTERRUPTIBLE, for scheduling or > swap delays) >=20 > --=20 > error compiling committee.c: too many arguments to function >=20 Do you want the preemption notifier work in before you will consider merging this set, or can that be a follow on? Eric --DiL7RhKs8rK9YGuF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBAgAGBQJO6OPUAAoJEKhG9nGc1bpJfh0P/27rntQ0sjv9E711ZQm01dhK 7K+sev5s2I0VtZHgNICjQ31D8Ct0PSSOhwvmrs3Fe8SMb+WU18B/NWN8NCX3AFN8 EjRL8846AGfrzAqdKZyezCbEq+q4gDoESst8bH2kXWiKfpeRu7v/K+trALpheS/B HM0B5pJ25hqqy6c18e2mX873WK0gvX2ZnRvitgChnnTGyC29yDh26Xc74mYC5iqP RJ2QYVb99Qc0L7E6263NHoaZOKsGntUNcCBE3H8g487ZEwGaGXL37Cc2+tszAo1x iu38AdVJwMvNlMlIXykHKA2bxhPSIYB4huooCTCy9oRApxV73Sn/N6IVFjN1loHi frDrI5LRHWiSE1lwYQhH5h6C5RGnBIRljjpOqAa5P4lrwbkuf6UV2zJj00m3M+Qz ynk216/CeHQfVtXHurHUK5i2L7D3K9DzM/DogaNCqwbd1jGHAIhaIiRtTzoMeqm0 MgdzqonV0xY6+Xe2MVAJpKL/gitnqIV1We7OAp0BjquQHM3nvNoyhPSrPwR1LEng gNbgQJ32qCPs4ydzS76KJRum7BUi0ai8dE7vu0EdBnUrrPBignEjt8v1EZinmjCl KHlQC7RW6VBjyre7mfOdPHPBCTw+gQ/4nq+u5qA4NqiEmLKmXaiEQ6MqqhTBFJDK gvFdAUa4KV6IToBMkm2T =FWT7 -----END PGP SIGNATURE----- --DiL7RhKs8rK9YGuF--