On 13/11/17 11:06, Quan Xu wrote: > From: Quan Xu <quan.xu0@xxxxxxxxx> > > So far, pv_idle_ops.poll is the only ops for pv_idle. .poll is called > in idle path which will poll for a while before we enter the real idle > state. > > In virtualization, idle path includes several heavy operations > includes timer access(LAPIC timer or TSC deadline timer) which will > hurt performance especially for latency intensive workload like message > passing task. The cost is mainly from the vmexit which is a hardware > context switch between virtual machine and hypervisor. Our solution is > to poll for a while and do not enter real idle path if we can get the > schedule event during polling. > > Poll may cause the CPU waste so we adopt a smart polling mechanism to > reduce the useless poll. > > Signed-off-by: Yang Zhang <yang.zhang.wz@xxxxxxxxx> > Signed-off-by: Quan Xu <quan.xu0@xxxxxxxxx> > Cc: Juergen Gross <jgross@xxxxxxxx> > Cc: Alok Kataria <akataria@xxxxxxxxxx> > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx Hmm, is the idle entry path really so critical to performance that a new pvops function is necessary? Wouldn't a function pointer, maybe guarded by a static key, be enough? A further advantage would be that this would work on other architectures, too. Juergen
