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Date: Tue, 25 Mar 2014 13:37:38 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC]Two ideas to optimize updating irq routing
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To: "Gonglei (Arei)" <arei.gonglei@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Cc: "Huangweidong (C)" <weidong.huang@huawei.com>, "gleb@redhat.com" <gleb@redhat.com>, "mst@redhat.com" <mst@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, "avi.kivity@gmail.com" <avi.kivity@gmail.com>, "Herongguang (Stephen)" <herongguang.he@huawei.com>

Il 25/03/2014 04:19, Gonglei (Arei) ha scritto:
> Based on discussions in:
> http://lists.gnu.org/archive/html/qemu-devel/2013-11/threads.html#03322
>
> About KVM_SET_GSI_ROUTING ioctl, I tested changing RCU to SRCU, but unfortunately
> it looks like SRCU's grace period is no better than RCU.

Really?  This is not what Christian Borntraeger claimed at 
http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/118083 -- in 
fact, Andrew Theurer is currently testing a variant of that patch and I 
was going to post it for 3.16.

Have you tried synchronize_srcu_expedited?  Unlike the RCU variant, you 
can use this function.

Paolo