2017-11-13 18:53 GMT+08:00 Juergen Gross <jgr...@suse.com>: > On 13/11/17 11:06, Quan Xu wrote: >> From: Quan Xu <quan....@gmail.com> >> >> 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...@gmail.com> >> Signed-off-by: Quan Xu <quan....@gmail.com> >> Cc: Juergen Gross <jgr...@suse.com> >> Cc: Alok Kataria <akata...@vmware.com> >> Cc: Rusty Russell <ru...@rustcorp.com.au> >> Cc: Thomas Gleixner <t...@linutronix.de> >> Cc: Ingo Molnar <mi...@redhat.com> >> Cc: "H. Peter Anvin" <h...@zytor.com> >> Cc: x...@kernel.org >> Cc: virtualizat...@lists.linux-foundation.org >> Cc: linux-ker...@vger.kernel.org >> Cc: xen-de...@lists.xenproject.org > > 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.
There is a "Adaptive halt-polling" which are merged to upstream more than two years ago avoids to thread the critical path and has already been ported to other architectures. https://lkml.org/lkml/2015/9/3/615 Regards, Wanpeng Li _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
