Re: [libvirt] [resend v2 0/7] Support cache tune in libvirt

On Tue, Feb 07, 2017 at 02:43:13PM +0800, Eli Qiao wrote: > > > -- > Eli Qiao > Sent with Sparrow (http://www.sparrowmailapp.com/?sig) > > > On Tuesday, 7 February 2017 at 3:03 AM, Marcelo Tosatti wrote: > > > On Mon, Feb 06, 2017 at 01:33:09PM -0200, Marcelo Tosatti wrote: > > > On Mon, Feb 06, 2017 at 10:23:35AM +0800, Eli Qiao wrote: > > > > This series patches are for supportting CAT featues, which also > > > > called cache tune in libvirt. > > > > > > > > First to expose cache information which could be tuned in capabilites XML. > > > > Then add new domain xml element support to add cacahe bank which will apply > > > > on this libvirt domain. > > > > > > > > This series patches add a util file `resctrl.c/h`, an interface to talk with > > > > linux kernel's sys fs. > > > > > > > > There are still some TODOs such as expose new public interface to get free > > > > cache information. > > > > > > > > Some discussion about this feature support can be found from: > > > > https://www.redhat.com/archives/libvir-list/2017-January/msg00644.html > > > > > > > > > > > > > > > > > > > > Two comments: > > > > > > 1) Please perform appropriate filesystem locking when accessing > > > resctrlfs, as described at: > > > > > > http://www.spinics.net/lists/linux-tip-commits/msg36754.html > > > > > > > > > > Sure. > > > > > > 2) > > > > > > <cachetune id='10' host_id='1' type='l3' size='3072' unit='KiB'/> > > > > > > [b4c270b5-e0f9-4106-a446-69032872ed7d]# cat tasks > > > 8654 > > > [b4c270b5-e0f9-4106-a446-69032872ed7d]# pstree -p | grep qemu > > > |-qemu-kvm(8654)-+-{qemu-kvm}(8688) > > > | |-{qemu-kvm}(8692) > > > | `-{qemu-kvm}(8693) > > > > > > Should add individual vcpus to the "tasks" file, not the main QEMU > > > process. > > > > > > The NFV usecase requires exclusive CAT allocation for the vcpu which > > > runs the sensitive workload. > > > > > > Perhaps: > > > > > > <cachetune id='10' host_id='1' type='l3' size='3072' unit='KiB'/> > > > > > > Adds all vcpus that are pinned to the socket which cachebank with > > > host_id=1. > > > > > > <cachetune id='10' host_id='1' type='l3' size='3072' unit='KiB' vcpus=2,3/> > > > > > > Adds PID of vcpus 2 and 3 to resctrl directory created for this > > > allocation. > > > > > > > > > > > > > > > > Hmm.. in this case, we need to figure out what’s the pid of vcpus=2 and vcpu=3 and added them to the resctrl directory. > Yes and only the pids of vcpus=2 and vcpus=3, not of any other vcpus. > currently, I create a resctrl directory(called resctrl domain) for a VM so just put all task ids to it. > > this is my though: > > let say the vm has vcpus=0 1 2 3, and you want to let 0, 1 benefit cache on host_id=0, and 2, 3 on host_id=1 > > you will do: > > 1) > pin vcpus 0, 1 on the cpus of socket 0 > pin vcpus 2, 3 on the cpus of socket 1 > this can be done in vcputune > > 2) define cache tune like this: > <cachetune id='0' host_id=‘0' type='l3' size='3072' unit='KiB'/> > <cachetune id='1' host_id='1' type='l3' size='3072' unit='KiB'/> > > in libvirt: > we create a resctrl directory naming with the VM’s uuid > and set schemata for each socket 0, and socket 1, put all qemu tasks ids into tasks file, this will work fine. > No, please don't do this. > please be note that in a resctrl directory, we can define schemata for each socket id separately. Please do not put vcpus automatically into the reservations. Its necessary to have certain vcpus in a reservation and some not. For example: 2 vcpu guest, vcpu0 pinned to socket 0 cpu0, vcpu1 pinned to socket 0 cpu1. <cachetune id='0' host_id=‘0' type='l3' size='3072' unit='KiB'/> We want _only_ vcpu1 to be part of this reservation, and not vcpu0 (want vcpu0 to use the default group, ie. schemata file at /sys/fs/resctrl/schemata So please have the ability to add vcpus to the XML syntax: <cachetune id='0' host_id=‘0' type='l3' size='3072' unit='KiB' vcpus='1'/> or <cachetune id='0' host_id=‘0' type='l3' size='3072' unit='KiB' vcpus='2,3'/>

This also allows different sizes to be specified. > > 3) CDP / non-CDP convertion. > > > > In case the size determination has been performed with non-CDP, > > to emulate such allocation on a CDP host, > > it would be good to allow both code and data allocations to share > > the CBM space: > > > > > > IOM, I don’t think it’s good to have this. > in libvirt capabilities xml, the application will get to know if the host support cdp or not. > > > > > <cachetune id='10' host_id='1' type='l3data' size='3072' unit='KiB'/> > > <cachetune id='10' host_id='1' type='l3code' size='3072' unit='KiB'/> > > > > Perhaps if using the same ID? > > > > I am open to hear about what other’s say, > > > > > > > Other than that, testing looks good. > > > > Thanks for the testing. >