> -----Original Message----- > From: Tian, Kevin > Sent: Thursday, March 10, 2016 6:06 PM > To: Jan Beulich <jbeul...@suse.com> > Cc: Andrew Cooper <andrew.coop...@citrix.com>; Dario Faggioli > <dario.faggi...@citrix.com>; David Vrabel <david.vra...@citrix.com>; > GeorgeDunlap <george.dun...@citrix.com>; Lars Kurth <lars.ku...@citrix.com>; > George Dunlap <george.dun...@eu.citrix.com>; Ian Jackson > <ian.jack...@eu.citrix.com>; Wu, Feng <feng...@intel.com>; xen- > de...@lists.xen.org; Konrad Rzeszutek Wilk <konrad.w...@oracle.com> > Subject: RE: vmx: VT-d posted-interrupt core logic handling > > > Hi, Jan, > > I'm thinking your earlier idea about evenly distributed list: > > -- > Ah, right, I think that limitation was named before, yet I've > forgotten about it again. But that only slightly alters the > suggestion: To distribute vCPU-s evenly would then require to > change their placement on the pCPU in the course of entering > blocked state. > -- > > Actually after more thinking, there is no hard requirement that > the vcpu must block on the pcpu which is configured in 'NDST' > of that vcpu's PI descriptor. What really matters, is that the > vcpu is added to the linked list of the very pcpu, then when PI > notification comes we can always find out the vcpu struct from > that pcpu's linked list. Of course one drawback of such placement > is additional IPI incurred in wake up path. > > Then one possible optimized policy within vmx_vcpu_block could > be: > > (Say PCPU1 which VCPU1 is currently blocked on) > - As long as the #vcpus in the linked list on PCPU1 is below a > threshold (say 16), add VCPU1 to the list. NDST set to PCPU1; > Upon PI notification on PCPU1, local linked list is searched to > find VCPU1 and then VCPU1 will be unblocked on PCPU1; > > - Otherwise, add VCPU1 to PCPU2 based on a simple distribution > algorithm (based on vcpu_id/vm_id). VCPU1 still blocks on PCPU1 > but NDST set to PCPU2. Upon notification on PCPU2, local linked > list is searched to find VCPU1 and then an IPI is sent to PCPU1 to > unblock VCPU1; > > Feng, do you see any overlook here? :-)
Kevin, thanks for the suggestion, it sounds a good idea, I will think it a bit more and do some trials based on it. Thanks, Feng > > Thanks > Kevin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel