Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751453AbdIAGy3 (ORCPT ); Fri, 1 Sep 2017 02:54:29 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:37798 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000AbdIAGy0 (ORCPT ); Fri, 1 Sep 2017 02:54:26 -0400 X-Google-Smtp-Source: ADKCNb50EmFqT5rfCJIGbyjwq7GIUfCISKaNQFKntLmES1pDRYT5M4rhwfSYQ3UB7XTk3ptJPi815g== Subject: Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops To: Konrad Rzeszutek Wilk , xen-devel@lists.xensource.com, jgross@suse.com, Boris Ostrovsky Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, wanpeng.li@hotmail.com, mst@redhat.com, pbonzini@redhat.com, tglx@linutronix.de, rkrcmar@redhat.com, dmatlack@google.com, agraf@suse.de, peterz@infradead.org, linux-doc@vger.kernel.org, Quan Xu , Jeremy Fitzhardinge , Chris Wright , Alok Kataria , Rusty Russell , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Andy Lutomirski , "Kirill A. Shutemov" , Pan Xinhui , Kees Cook , virtualization@lists.linux-foundation.org References: <1504007201-12904-1-git-send-email-yang.zhang.wz@gmail.com> <1504007201-12904-2-git-send-email-yang.zhang.wz@gmail.com> <20170829135548.GG32175@char.us.oracle.com> From: Yang Zhang Message-ID: Date: Fri, 1 Sep 2017 14:50:28 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20170829135548.GG32175@char.us.oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5022 Lines: 135 On 2017/8/29 21:55, Konrad Rzeszutek Wilk wrote: > 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? Hi Konard, I didn't test it in Xen side since i don't have the environment but i can add it for Xen in next version if you think it is useful to Xen as well. > >> --- >> 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 >> -- Yang Alibaba Cloud Computing