From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Date: Tue, 29 Aug 2017 09:55:48 -0400 Message-ID: <20170829135548.GG32175@char.us.oracle.com> References: <1504007201-12904-1-git-send-email-yang.zhang.wz@gmail.com> <1504007201-12904-2-git-send-email-yang.zhang.wz@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1504007201-12904-2-git-send-email-yang.zhang.wz@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Yang Zhang , xen-devel@lists.xensource.com, jgross@suse.com, Boris Ostrovsky Cc: Jeremy Fitzhardinge , rkrcmar@redhat.com, kvm@vger.kernel.org, mst@redhat.com, peterz@infradead.org, Pan Xinhui , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , Alok Kataria , wanpeng.li@hotmail.com, x86@kernel.org, Ingo Molnar , Kees Cook , Chris Wright , Andy Lutomirski , dmatlack@google.com, tglx@linutronix.de, Quan Xu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, "Kirill A. Shutemov" List-Id: xen-devel@lists.xenproject.org On Tue, Aug 29, 2017 at 11:46:35AM +0000, Yang Zhang wrote: > So far, pv_idle_ops.poll is the only ops for pv_idle. .poll is called in > idle path which will polling 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 come from the vmexit which is a > hardware context switch between VM 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 > Signed-off-by: Quan Xu > Cc: Jeremy Fitzhardinge > Cc: Chris Wright > Cc: Alok Kataria > Cc: Rusty Russell > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: x86@kernel.org > Cc: Peter Zijlstra > Cc: Andy Lutomirski > Cc: "Kirill A. Shutemov" > Cc: Pan Xinhui > Cc: Kees Cook > Cc: virtualization@lists.linux-foundation.org > Cc: linux-kernel@vger.kernel.org Adding xen-devel. Juergen, we really should replace Jeremy's name with xen-devel or your name.. Wasn't there an patch by you that took some of the mainternship over it? > --- > arch/x86/include/asm/paravirt.h | 5 +++++ > arch/x86/include/asm/paravirt_types.h | 6 ++++++ > arch/x86/kernel/paravirt.c | 6 ++++++ > 3 files changed, 17 insertions(+) > > diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h > index 9ccac19..6d46760 100644 > --- a/arch/x86/include/asm/paravirt.h > +++ b/arch/x86/include/asm/paravirt.h > @@ -202,6 +202,11 @@ static inline unsigned long long paravirt_read_pmc(int counter) > > #define rdpmcl(counter, val) ((val) = paravirt_read_pmc(counter)) > > +static inline void paravirt_idle_poll(void) > +{ > + PVOP_VCALL0(pv_idle_ops.poll); > +} > + > static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries) > { > PVOP_VCALL2(pv_cpu_ops.alloc_ldt, ldt, entries); > diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h > index 9ffc36b..cf45726 100644 > --- a/arch/x86/include/asm/paravirt_types.h > +++ b/arch/x86/include/asm/paravirt_types.h > @@ -324,6 +324,10 @@ struct pv_lock_ops { > struct paravirt_callee_save vcpu_is_preempted; > } __no_randomize_layout; > > +struct pv_idle_ops { > + void (*poll)(void); > +} __no_randomize_layout; > + > /* This contains all the paravirt structures: we get a convenient > * number for each function using the offset which we use to indicate > * what to patch. */ > @@ -334,6 +338,7 @@ struct paravirt_patch_template { > struct pv_irq_ops pv_irq_ops; > struct pv_mmu_ops pv_mmu_ops; > struct pv_lock_ops pv_lock_ops; > + struct pv_idle_ops pv_idle_ops; > } __no_randomize_layout; > > extern struct pv_info pv_info; > @@ -343,6 +348,7 @@ struct paravirt_patch_template { > extern struct pv_irq_ops pv_irq_ops; > extern struct pv_mmu_ops pv_mmu_ops; > extern struct pv_lock_ops pv_lock_ops; > +extern struct pv_idle_ops pv_idle_ops; > > #define PARAVIRT_PATCH(x) \ > (offsetof(struct paravirt_patch_template, x) / sizeof(void *)) > diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c > index bc0a849..1b5b247 100644 > --- a/arch/x86/kernel/paravirt.c > +++ b/arch/x86/kernel/paravirt.c > @@ -128,6 +128,7 @@ static void *get_call_destination(u8 type) > #ifdef CONFIG_PARAVIRT_SPINLOCKS > .pv_lock_ops = pv_lock_ops, > #endif > + .pv_idle_ops = pv_idle_ops, > }; > return *((void **)&tmpl + type); > } > @@ -312,6 +313,10 @@ struct pv_time_ops pv_time_ops = { > .steal_clock = native_steal_clock, > }; > > +struct pv_idle_ops pv_idle_ops = { > + .poll = paravirt_nop, > +}; > + > __visible struct pv_irq_ops pv_irq_ops = { > .save_fl = __PV_IS_CALLEE_SAVE(native_save_fl), > .restore_fl = __PV_IS_CALLEE_SAVE(native_restore_fl), > @@ -471,3 +476,4 @@ struct pv_mmu_ops pv_mmu_ops __ro_after_init = { > EXPORT_SYMBOL (pv_mmu_ops); > EXPORT_SYMBOL_GPL(pv_info); > EXPORT_SYMBOL (pv_irq_ops); > +EXPORT_SYMBOL (pv_idle_ops); > -- > 1.8.3.1 >