Re: [libvirt] [V4] RFC for support cache tune(CAT) in libvirt

On Fri, Jan 13, 2017 at 09:38:44AM +0800, 乔立勇(Eli Qiao) wrote: > > virsh capabilities > > > > <cache> > > <bank id='0, 'type="l3" size="56320" units="KiB" cpus="0,1,2,6,7,8"/> > <--------------------- level 3 cache is per socket, so group them by > socket id > > <control unit="KiB" min="2816"/> > > <bank id='1', type="l3" size="56320" units="KiB" > cpus="3,4,5,9,10,11"/> > > <bank id='2' type="l2" size="256" units="KiB" cpus="0"/> > > <bank id='3' type="l2" size="256" units="KiB" cpus="1"/> > > <bank id='4' type="l2" size="256" units="KiB" cpus="2"/> > > <bank id='5' type="l2" size="256" units="KiB" cpus="3"/> > > <bank id='6' type="l2" size="256" units="KiB" cpus="4"/> > > ... > > <cache> > > > > Opens > > 1. how about add socket id to bank for bank type = l3 ? This isn't needed - with the 'cpu' IDs here, the application can look at the topology info in the capabilities to find out what socket the logical CPU is part of. > 2. do we really want to expose l2/l3 cache for now , they are per core > resource and linux kernel don't support l2 yet (depend no hardware)? We dont't need to report all levels of cache - we just need the XML schema to allow it by design. > 3. if enable CDP in resctrl, for bank type=l3 , it will be split to > l3data l3code, should expose this ability. > > <bank type="l3" size="56320" units="KiB" cpus="0,1,2,6,7,8"/> > <--------------------- level 3 cache is per socket, so group them by > socket id > > <control unit="KiB" min="2816" cdp="enabled"/> 'cdp' is intel specific terminology. We need to use some more generic description. Perhaps we want this when CDP is enabled: <control unit="KiB" min="2816" scope="data"/> <control unit="KiB" min="2816" scope="code"/> and when its disabled just <control unit="KiB" min="2816" scope="both"/> If we have this scope option, then we'll need it when reporting too... > ## Provide a new API to get the avail cache on each bank, such as the > output are: > > > > id=0 > > type=l3 ...eg scope=data > avail=56320 > > total = ?? <--------- do we need this? That info is static and available from capabilities, so we don't need to repeat it here IMHO. > > > > id=1 > > type=l3 > > avail=56320 > > > > id=3 > > type=l2 > > avail=256 > > > > Opens: > > · Don't expose the avail cache information if the host can not do > the allocation of that type cache(eg, for l2 currently) ? This api should only report info about cache banks that support allocation/. > · We can not make all of the cache , the reservation amount is the > min_cbm_len (=1) * min_unit . If there is some minimum amount which is reserved and cannot be allocated, we should report that in the capabilities XML too. eg <control unit="KiB" min="2816" reserved="5632" scope="both"/> > · do we need to expose total? No, that's available in capabilities XML > ## enable CAT for a domain > > > > 1 Domain XML changes > > > > <cputune> > > <cache id="1" host_id="0" type="l3" size="5632" unit="KiB"/> > > <cache id="2" host_id="1" type="l3" size="5632" unit="KiB"/> > > > > <cpu_cache vcpus="0-3" id="1"/> > > <cpu_cache vcpus="4-7" id="2"/> > > <iothread_cache iothreads="0-1" id="1"/> > > <emulator_cache id="2"/> > > </cputune> > > 2. Extend cputune command ? Do we need the ability to change cache allocation for a running guest ? If so, then we need to extend cputune command, if not we can ignore it.