From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: [PATCH v5 7/9] x86, xen: support vcpu preempted check Date: Fri, 21 Oct 2016 07:08:19 +0200 Message-ID: <7ebcc196-e483-097c-41c8-070b46297c9d@suse.com> References: <1476998874-2089-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1476998874-2089-8-git-send-email-xinhui.pan@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, pbonzini@redhat.com, bsingharora@gmail.com, boqun.feng@gmail.com, borntraeger@de.ibm.com, rkrcmar@redhat.com, David Vrabel , Boris Ostrovsky To: Pan Xinhui , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org Return-path: In-Reply-To: <1476998874-2089-8-git-send-email-xinhui.pan@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Corrected xen-devel mailing list address, added other Xen maintainers On 20/10/16 23:27, Pan Xinhui wrote: > From: Juergen Gross > > Support the vcpu_is_preempted() functionality under Xen. This will > enhance lock performance on overcommitted hosts (more runnable vcpus > than physical cpus in the system) as doing busy waits for preempted > vcpus will hurt system performance far worse than early yielding. > > A quick test (4 vcpus on 1 physical cpu doing a parallel build job > with "make -j 8") reduced system time by about 5% with this patch. > > Signed-off-by: Juergen Gross > Signed-off-by: Pan Xinhui > --- > arch/x86/xen/spinlock.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c > index 3d6e006..74756bb 100644 > --- a/arch/x86/xen/spinlock.c > +++ b/arch/x86/xen/spinlock.c > @@ -114,7 +114,6 @@ void xen_uninit_lock_cpu(int cpu) > per_cpu(irq_name, cpu) = NULL; > } > > - > /* > * Our init of PV spinlocks is split in two init functions due to us > * using paravirt patching and jump labels patching and having to do > @@ -137,6 +136,8 @@ void __init xen_init_spinlocks(void) > pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); > pv_lock_ops.wait = xen_qlock_wait; > pv_lock_ops.kick = xen_qlock_kick; > + > + pv_lock_ops.vcpu_is_preempted = xen_vcpu_stolen; > } > > /* >