On 20 January 2016 at 19:44, Christian Borntraeger <borntrae...@de.ibm.com> wrote: > the TCG emulation of QEMU does work without allocatr_pgste. > vm.allocate_pgste=1 is necessary to use the KVM kernel module (which is used > by qemu in kvm mode) > > The main difference is that this uses 4k page tables instead of 2k page > tables on s390. So enabling pgstes will increase the page table > overhead. The difference is usually pretty small, but might become > noticeable when you have things like a big database with hundreds of > processes accessing a big area of shared memory. >
Thank you for the info. > Maybe something like > # cat /etc/modprobe.d/99-kvm.conf > install kvm /sbin/sysctl vm.allocate_pgste=1; /sbin/modprobe --ignore-install > kvm > remove kvm /sbin/sysctl vm.allocate_pgste=0; /sbin/modprobe -r > --ignore-remove kvm > > would be good enough? > In newer kernel config we have kvm module as a built in, rather than a module. I was thinking to move vm.allocate_pgste=1 from procps package (installed everywhere) to qemu package (installed when going to run VMs). -- Regards, Dimitri. -- 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/1533646 Title: Could you set vm.allocate_pgste = 1 by default? Status in linux package in Ubuntu: Incomplete Bug description: Hello, to use qemu one needs vm.allocate_pgste = 1, on kernels that support that setting e.g. s390x. I'm now setting it with a sysctl.d snippet in procps package, however I was wondering if it could be set by default. Or not. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1533646/+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
