So, I've had an exciting evening armed with ftrace and a kernel debugger. I'm questioning my own sanity a bit here, but I'm fairly sure at this point that setting ftrace going and loading the kernel debugging module (I'm using kgdboe here because I'm on AWS) stop whatever the issue is from happening - kswapd0's CPU usage doesn't even increase with them enabled, never mind run out of control. However, it *is* possible to trigger issue and then enable ftrace or load the debug module and break in. I haven't found the debugger super useful, though I did manage to break into kswapd0 while it was doing things at one point, so it's potentially an option if necessary. ftrace looked more useful; I've attached a trace of an arbitrary time slice taken with the issue happening. Happy to do extra work with either if these if anyone has further ideas.
** Attachment added: "ftrace of kswapd0 exhibiting issue" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518457/+attachment/4549568/+files/ftrace4 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1518457 Title: kswapd0 100% CPU usage Status in linux package in Ubuntu: In Progress Bug description: As per bug 721896 and various others: I'm on an AWS t2.micro instance (Xeon E5-2670, 991MiB of memory). Occasionally (about once a day), kswapd0 falls into a busy loop and spins on 100% CPU usage indefinitely. This can be provoked by copying/writing large files (e.g. dding a 256MB file), but it happens occasionally otherwise. System memory usage (not including buffers/caches) currently sits at 36%, which is typical[1]. Initially I had no swap space configured; I've since tried enabling a 256MB swap file, but the problem continues to occur and no swap space is used. The system can be recovered with `echo 1 > /proc/sys/vm/drop_caches`. Happy to provide further information/take further debugging actions. [1] Full output from `free`: total used free shared buffers cached Mem: 1014936 483448 531488 28556 9756 112700 -/+ buffers/cache: 360992 653944 Swap: 262140 0 262140 ProblemType: Bug DistroRelease: Ubuntu 15.10 Package: linux-image-4.2.0-18-generic 4.2.0-18.22 ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3 Uname: Linux 4.2.0-18-generic x86_64 AlsaDevices: total 0 crw-rw---- 1 root audio 116, 1 Nov 19 19:40 seq crw-rw---- 1 root audio 116, 33 Nov 19 19:40 timer AplayDevices: Error: [Errno 2] No such file or directory: 'aplay' ApportVersion: 2.19.1-0ubuntu5 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord' AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: N/A Date: Fri Nov 20 20:44:30 2015 Ec2AMI: ami-1c552a76 Ec2AMIManifest: (unknown) Ec2AvailabilityZone: us-east-1d Ec2InstanceType: t2.micro Ec2Kernel: unavailable Ec2Ramdisk: unavailable IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig' Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99 MachineType: Xen HVM domU PciMultimedia: ProcEnviron: TERM=screen PATH=(custom, no user) LANG=en_US.UTF-8 SHELL=/bin/bash ProcFB: 0 xen ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-18-generic root=UUID=35bc01f4-4602-4823-976e-508edef899df ro console=tty1 console=ttyS0 net.ifnames=0 RelatedPackageVersions: linux-restricted-modules-4.2.0-18-generic N/A linux-backports-modules-4.2.0-18-generic N/A linux-firmware N/A RfKill: Error: [Errno 2] No such file or directory: 'rfkill' SourcePackage: linux UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev' UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 05/06/2015 dmi.bios.vendor: Xen dmi.bios.version: 4.2.amazon dmi.chassis.type: 1 dmi.chassis.vendor: Xen dmi.modalias: dmi:bvnXen:bvr4.2.amazon:bd05/06/2015:svnXen:pnHVMdomU:pvr4.2.amazon:cvnXen:ct1:cvr: dmi.product.name: HVM domU dmi.product.version: 4.2.amazon dmi.sys.vendor: Xen To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518457/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
