Re: [libvirt] [PATCHv6 0/6] Add virNodeGetCPUStats() API

On Fri, May 27, 2011 at 02:34:50PM +0100, Daniel P. Berrange wrote: > On Wed, May 25, 2011 at 03:01:29PM +0900, Minoru Usui wrote: > > Hi, > > > > This is v6 of virNodeGetCPUTimeParameters() API. > > (This time, I rename it to virNodeGetCPUStats()) > > It returns cpu utilization or > > cumulative cpu time of the node from /proc/stat since node boots up. > > This patch only supports linux host. > > The code in this patch series looks fine to me now. I would > ACK the whole series, but I have one design question I should > have asked previously. > > This API returns CPU information for the host as a whole. > Historically, when adding an API like this, someone has always > then asked for a per-CPU breakdown of the same data. > > So I wonder if we should add a parameter for the CPU num > to the API: > > int virNodeGetCPUStats (virConnectPtr conn, > int cpuNum, > virCPUStatsPtr params, > int *nparams, > unsigned int flags); > > And have a constant for getting the host data as a whole: > > #define VIR_NODE_CPU_STATS_ALL_CPUS -1 > > so if you want to get individual data for each CPU you > can do > > virNodeGetCPUStats(conn, 0, params, nparams, flags); > virNodeGetCPUStats(conn, 1, params, nparams, flags); > virNodeGetCPUStats(conn, 2, params, nparams, flags); > virNodeGetCPUStats(conn, 3, params, nparams, flags); > > But if you just want the data for the host as a whole > you can do > > virNodeGetCPUStats(conn, VIR_NODE_CPU_STATS_ALL_CPUS, > params, nparams, flags); > > The /proc/stat file already has the data we need for both > these styles > > $ grep cpu /proc/stat > cpu 2632143 17400 1341532 32819705 1177560 674 21606 0 11997 0 > cpu0 1263069 9280 596278 16274365 620428 631 17303 0 6131 0 > cpu1 1369073 8119 745254 16545339 557131 43 4302 0 5865 0 Agreed, similary as for the virNodeGetMemoryStats() patch set, the patches looks good enough for being applied but doing the suggested changes (i.e. adding a new argument for the cpu number or the cell number). For virsh command I would make querying all the default but just add an optionnal argument --cpu virsh nodecpustats --cpu cpunumber and similary on the memry patch set add an optional --cell argument virsh nodememstats --cell cellnumber That way the API and virsh command are ready for more precise use and we won't need to make a second set of APIs. thanks !

Daniel -- Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/ daniel(a)veillard.com | Rpmfind RPM search engine http://rpmfind.net/ http://veillard.com/ | virtualization library http://libvirt.org/