On Mon, Jan 23, 2017 at 12:50 PM, Laszlo Ersek <[email protected]> wrote:
> On 01/23/17 20:02, Alex Williamson wrote: > > > isolcpus > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/ > linux.git/tree/Documentation/admin-guide/kernel-parameters.txt#n1669 > > BTW, do you know a method to massage isolcpus without a host reboot? The > last paragraph of the linked section doesn't look promising ("... can > cause problems and suboptimal load balancer performance"). > > Sometimes the same host is temporarily dedicated to run a VM where > latency doesn't matter much, but throughput does (example: distcc server > with assigned 1Gbit NIC VF); and sometimes the host is dedicated to a VM > where isolcpus would be beneficial to latency (example: interactive 3D > stuff with assigned GPU). > > It's quite a pain to reboot the host just to switch between these two; > that sort of eliminates the benefits of virtualization. Furthermore, > > - the LUKS password for the host needs to be entered again, > - startup of guests with bridged virtual NICs has to await host DHCP for > internet connectivity again, > - for remote management with virt-manager, the multiplexing SSH master > process on the client has to be re-launched (and then virt-manager has > to be reconnected over the local muxer socket), > - etc > No need to sell me on it, I agree it'd be useful. I imagine there's some way to do this with cgroups, ie. dynamically add/remove cpus from the default init process cpuset, but it hasn't nagged at me enough to find time to investigate further. It seems like someone had reported a more dynamic setup. Thanks, Alex
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