On Wed, May 08, 2019 at 12:15:19AM +0200, Peter Zijlstra wrote: > On Tue, May 07, 2019 at 03:56:49PM -0300, Marcelo Tosatti wrote: > > > > Certain workloads perform poorly on KVM compared to baremetal > > due to baremetal's ability to perform mwait on NEED_RESCHED > > bit of task flags (therefore skipping the IPI). > > > > This patch introduces a configurable busy-wait delay before entering the > > architecture delay routine, allowing wakeup IPIs to be skipped > > (if the IPI happens in that window). > > > > The real-life workload which this patch improves performance > > is SAP HANA (by 5-10%) (for which case setting idle_spin to 30 > > is sufficient). > > > > This patch improves the attached server.py and client.py example > > as follows: > > > > Host: 31.814230202231556 > > Guest: 38.17718765199993 (83 %) > > Guest, idle_spin=50us: 33.317709898000004 (95 %) > > Guest, idle_spin=220us: 32.27826551499999 (98 %) > > > > Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> > > Thanks for the CC.. > > NAK, this is something that should live in a virt idle governor or > something along those lines. Ok, makes sense, will rework the patch!
