From mboxrd@z Thu Jan 1 00:00:00 1970 From: jan.glauber@caviumnetworks.com (Jan Glauber) Date: Mon, 13 Nov 2017 19:40:46 +0100 Subject: RCU stall with high number of KVM vcpus In-Reply-To: <7dda7be2-f392-8056-d4d3-372bb867729a@arm.com> References: <20171113131000.GA10546@hc> <2832f775-3cbe-d984-fe4f-e018642b6f1d@arm.com> <20171113173552.GA13282@hc> <7dda7be2-f392-8056-d4d3-372bb867729a@arm.com> Message-ID: <20171113184046.GA14678@hc> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Nov 13, 2017 at 06:11:19PM +0000, Marc Zyngier wrote: > On 13/11/17 17:35, Jan Glauber wrote: > > On Mon, Nov 13, 2017 at 01:47:38PM +0000, Marc Zyngier wrote: [...] > >> Please elaborate. Messed in what way? Corrupted? The guest crashing? Or > >> is that a tooling issue? > > > > Every vcpu that oopses prints one line in parallel, so I get blocks like: > > [58880.179814] [] ret_from_fork+0x10/0x18 > > [58880.179834] [] ret_from_fork+0x10/0x18 > > [58880.179847] [] ret_from_fork+0x10/0x18 > > [58880.179873] [] ret_from_fork+0x10/0x18 > > [58880.179893] [] ret_from_fork+0x10/0x18 > > [58880.179911] [] ret_from_fork+0x10/0x18 > > [58880.179917] [] ret_from_fork+0x10/0x18 > > [58880.180288] [] ret_from_fork+0x10/0x18 > > [58880.180303] [] ret_from_fork+0x10/0x18 > > [58880.180336] [] ret_from_fork+0x10/0x18 > > [58880.180363] [] ret_from_fork+0x10/0x18 > > [58880.180384] [] ret_from_fork+0x10/0x18 > > [58880.180415] [] ret_from_fork+0x10/0x18 > > [58880.180461] [] ret_from_fork+0x10/0x18 > > > > I can send the full log if you want to have a look. > > Sure, send that over (maybe not over email though). Here is the guest dmesg: http://paste.ubuntu.com/25955682/ And the host dmesg as it might have been too big for the lists: http://paste.ubuntu.com/25955699/ > Can you send me your kernel configuration as well? I wonder if we're not > seeing interactions with things like KSM and the like... It was plain arm64 defconfig but I disabled HAVE_KVM_CPU_RELAX_INTERCEPT. Not that it had an impact, just tried. http://paste.ubuntu.com/25955726/ --Jan