Messages in this thread | | | Subject | Re: [PATCH RFC v3 1/6] x86/paravirt: Add pv_idle_ops to paravirt ops | From | Juergen Gross <> | Date | Mon, 13 Nov 2017 11:53:52 +0100 |
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On 13/11/17 11:06, Quan Xu wrote: > From: Quan Xu <quan.xu0@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.wz@gmail.com> > Signed-off-by: Quan Xu <quan.xu0@gmail.com> > Cc: Juergen Gross <jgross@suse.com> > Cc: Alok Kataria <akataria@vmware.com> > Cc: Rusty Russell <rusty@rustcorp.com.au> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: x86@kernel.org > Cc: virtualization@lists.linux-foundation.org > Cc: linux-kernel@vger.kernel.org > Cc: xen-devel@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.
Juergen
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