You're right. Unfortunately with virtual machines that doesn't always work. You can enable it manually but that's more inefficient because the Kernel can't use

You're right. Unfortunately with virtual machines that doesn't always work. You can enable it manually but that's more inefficient because the Kernel can't use paravirtualization for clock then. I stumbled upon this a month ago: https://ddnet.tw/irclogs/2016-05-17.log https://ddnet.tw/irclogs/2016-05-17.log 21:37 <@deen> A third of the sys calls of a DDNet server are recfrom and sendto each 21:37 <@deen> they always occur in large chunks, so ideal for sendmmsg/recvmmsg 21:38 <@deen> the last third are mostly strange time and gettimeofday calls, I thought I got rid of most of them 21:40 <@deen> server with 30 players causes 3000 syscalls a second 22:00 <@deen> PACKET_MMAP is very cool, reading packets with 0 syscalls, too bad it's not for regular applications (requires root, doesn't work with normal udp socket): https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt 22:04 <@deen> and then the glibc version matters a lot for syscalls. new versions of glibc don't syscall at all for gettimeofday 22:05 <@deen> (or something else is causing that, not sure yet) 22:13 <@deen> Reading the glibc implementation, that's done by vDSO, interesting: http://man7.org/linux/man-pages/man7/vdso.7.html 22:32 <@deen> totally confused why some of our servers use vdso gettimeofday, others not even though they have more recent kernel and glibc 22:41 <@deen> ok, probably depends on the underlying clock that the vps uses. pvclock is used with kvm and doesn't support vdso. but looks like there's some progress being made: https://lkml.org/lkml/2015/12/9/914