Re: [libvirt] "[V3] RFC for support cache tune in libvirt"

hi, It's really good to have you get involved to support CAT in libvirt/OpenStack. replied inlines. 2017-01-11 20:19 GMT+08:00 Marcelo Tosatti <mtosatti(a)redhat.com&gt;: My plan's expose new options: virsh cachetune kvm02 --l3data.count 2 --l3code.count 2 Please notes, you can use only l3 or l3data/l3code(if enable cdp while mount resctrl fs) yes, it is the contiguous regions cbm or in another word it's the default cbm represent's cache value. resctrl doesn't allow set non-contiguous cbm (which is restricted by hardware) yes, it is. resource_id == cacheid I don't think it's good to let user specify cache-ids while doing cache allocation. the cache ids used should rely on what cpu affinity the vm are setting. eg. 1. for those host who has only one cache id(one socket host), we don't need to set cache id 2. if multiple cache ids(sockets), user should set vcpu -> pcpu mapping (define cpuset for a VM), then we (libvirt) need to compute how much cache on which cache id should set. Which is to say, user should set the cpu affinity before cache allocation. I know that the most cases of using CAT is for NFV. As far as I know, NFV is using NUMA and cpu pining (vcpu -> pcpu mapping), so we don't need to worry about on which cache id we set the cache size. So, just let user specify cache size(here my propose is cache unit account) and let libvirt detect on which cache id set how many cache. I accept this, I propose to expose minimum unit size because of I'd like to let using specify the unit count(which as you say this is not good), as you know the minimum unit size is decided by hard ware eg on a host, we have 56320 KiB cache, and the max cbm length is 20 (fffff), so the minimum cache should be 56320/20 = 2816 KiB if we allow use specify cache size instead of cache unit count, user may set the cache as 2817 KiB, and we should round up it to 2816 * 2, there will be 2815 KiB wasted. Anyway , I am open to using KiB size and let libvirt to calculate the cbm bits, am thinking if we need to tell the actual_cache_size is up to 5632 KiB even they wants 2816 KiB cache. Hmm.. as I can see libvirt is just an user space API, not sure if whether in libvirt we bypass some low level detail.. > Thanks! > -- > libvir-list mailing list > libvir-list(a)redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list -- Regards Eli 天涯无处不重逢 a leaf duckweed belongs to the sea , where not to meet in life