On Fri, 15 Aug 2008 13:26:43 -0400 Fabian Ischia <f_ischia@xxxxxxxxxxx> wrote: > I've started using bridges at the office because I need to connect Virtual Machines (User-Mode-Linux). I've noticed that it causes a huge increase in context switches. > The context switches seem to be limited somehow (I guess some kernel mechanism to prevent going wild). The context switches, even though they're cheap, also account for some 8-10% of CPU. > I've checked with some more knowledgeable people than me and they said in a heavy loaded server I should expect something around 30K but I'm around 1M and that's with the machine just sitting idle. > Does anyone know if there is an actual bug, and the appropriate patch to fix it; or whether it is considered OK this behavior? > > Fabian > > Running vmstat I see: > Without bridges: > 1 0 187312 58088 32144 338636 0 0 0 0 189 997 83 1 17 0 > 1 0 187312 57948 32144 338636 0 0 0 0 140 576 25 1 74 0 > 1 0 187312 58088 32144 338636 0 0 0 0 168 777 83 1 17 0 > 1 0 187312 58016 32144 338636 0 0 0 0 154 655 26 1 73 0 > 1 0 187312 57960 32144 338636 0 0 0 0 137 500 82 1 17 0 > 1 0 187312 58088 32144 338636 0 0 0 0 154 611 25 1 74 0 > 1 0 187312 57960 32144 338636 0 0 0 0 135 525 83 1 17 0 > > With 4 bridges idle (no traffic on the interfaces) > 1 0 187312 50864 32276 338632 0 0 0 0 139 134920 81 4 15 0 > 1 0 187312 51012 32276 338632 0 0 0 0 178 145827 24 3 72 0 > 1 0 187312 50880 32276 338632 0 0 0 36 180 152482 82 3 16 0 > 1 0 187312 50808 32276 338636 0 0 0 0 145 126225 25 2 72 0 > 1 0 187312 50888 32284 338628 0 0 0 56 162 136169 82 2 16 0 > 1 0 187312 50820 32284 338636 0 0 0 0 207 112448 26 3 71 0 > 1 0 187312 50740 32284 338636 0 0 0 0 148 163085 82 4 15 0 > > The precedent metrics are from my desktop machine, on the actual host where I have more bridges. > 0 0 0 679748 34448 2404840 0 0 0 0 67 928669 3 10 86 0 > 0 0 0 679748 34448 2404840 0 0 0 0 89 884379 2 9 90 0 > 0 0 0 679748 34448 2404840 0 0 0 0 66 924828 2 10 88 0 > 0 0 0 679748 34456 2404840 0 0 0 4 67 906076 5 8 87 0 > 0 0 0 679748 34456 2404840 0 0 0 0 67 920194 1 9 91 0 > 0 0 0 679748 34456 2404840 0 0 0 0 89 905816 1 11 91 0 > 0 0 0 679748 34464 2404840 0 0 0 0 87 868858 3 10 91 0 Use oprofile to look at where the overhead is. _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
