Re: [ovs-discuss] Kernel vs User mode switch
> On Mar 26, 2017, at 5:33 PM, Michael Williams wrote: > > What are the advantages of running the kernel verses the user mode switch? I assume you're specifically asking about running DPDK in userspace. There are certain traffic patterns that can be significantly faster by bypassing the kernel and handling directly in userspace. But, by bypassing the kernel, you miss out on the functionality provided by the kernel, so those must be recreated. Some examples include: - QoS - Connection tracking (for firewalls) and NAT - An IP stack (for tunnel termination) - Some NIC offloads Those features are being added, but not all of them are complete yet, so if you need a particular functionality, you may need to check whether it has all the features you need. In the case of DPDK, there can be restrictions on the CPUs and NICs that are supported. Also, for optimal performance, DPDK typically uses dedicated cores, but there's options to run in an interrupt-driven model. --Justin ___ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
Re: [ovs-discuss] Kernel vs User mode switch
This is a weird response. This is the Open vSwitch list, so the original poster is asking about Open vSwitch. On Sun, Mar 26, 2017 at 10:13:19PM -0400, Daniel Lohin wrote: > No idea what you are talking about… in what? > > Generally speaking… a user application runs as fast as kernel, as long as it > doesn’t need to make system level calls (i.e. write files, network packets, > etc). The reason is the kernel needs to do a lot of things like, does the > person have permissions… This is called context switching. > > Running at the kernel level is always fast… there is never any context > switching.. > > now for the drawback… errors in programming in the kernel are disasterous… > major system crashes (the whole computer), really bad security issues, etc… > User mode is a lot safer, at least to the system itself (an error can still > result in the crashing of the app, or security problems with the app itself, > but not the entire system). > > We try to keep as much out of the kernel as possible, but there are some > areas where it is needed for performance reasons. > > > On Mar 26, 2017, at 8:33 PM, Michael Williams wrote: > > > > What are the advantages of running the kernel verses the user mode switch? > > > > ___ > discuss mailing list > disc...@openvswitch.org > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss ___ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
Re: [ovs-discuss] Kernel vs User mode switch
No idea what you are talking about… in what? Generally speaking… a user application runs as fast as kernel, as long as it doesn’t need to make system level calls (i.e. write files, network packets, etc). The reason is the kernel needs to do a lot of things like, does the person have permissions… This is called context switching. Running at the kernel level is always fast… there is never any context switching.. now for the drawback… errors in programming in the kernel are disasterous… major system crashes (the whole computer), really bad security issues, etc… User mode is a lot safer, at least to the system itself (an error can still result in the crashing of the app, or security problems with the app itself, but not the entire system). We try to keep as much out of the kernel as possible, but there are some areas where it is needed for performance reasons. > On Mar 26, 2017, at 8:33 PM, Michael Williams wrote: > > What are the advantages of running the kernel verses the user mode switch? > ___ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
