Re: [libvirt] [v7 00/10] Support cache tune in libvirt

-- Best regards Eli 天涯无处不重逢 a leaf duckweed belongs to the sea, where not to meet in life Sent with Sparrow (http://www.sparrowmailapp.com/?sig) On Sunday, 19 February 2017 at 10:51 PM, Marcelo Tosatti wrote: > > Hi Eli Qiao, > > Question about removing resctrlfs directories with empty "tasks" file. > > > /* This domain is not created by libvirt, so we don't care > * about the tasks, add a fake one to prevent > * virResCtrlRefresh > * remove it from sysfs */ > virResCtrlAddTask(p, 1); > virResCtrlAppendDomain(p); > > /* Refresh all domains', remove the domains which has no task ids. > * This will be used after VM pause, restart, destroy etc. > */ > static int > virResCtrlRefresh(void) > > Why are you doing this (removing directories which have no tasks in > them) ? The code should only read information from other > CAT reservations, not write to them. > > When a VM get shutdown, their pids will disappear from resctrl’s directory, we can check pids to see if VM get KIlled or not. The reason why I would like check if tasks file empty is that: there maybe cases that libvirtd not tracking VM’s status, and the VM gone, left a empty directory with no tasks assigned, and cause resource leak. I think I can refine this later, keep a pointer of ResDomain in VM’s private data and use that to destroy VM’s resctrl directory. but this won’t work for exception, still resource leak happened.

> This is not for cleanup purposes, since on VM shutdown the resctrlfs > directories are properly removed: > > /* Remove the Domain from sysfs, this should only success no pids in > * tasks > * of a partition. > */ > static > int virResCtrlRemoveDomain(const char *name) > { > char *path = NULL; > int rc = 0; > > if ((rc = virAsprintf(&path, "%s/%s", RESCTRL_DIR, name)) < 0) > return rc; > rc = rmdir(path); > VIR_FREE(path); > return rc; > } > > Should not write to other directories 'tasks' file. Other Apps can have a lock to resctrl before it write tasks to prevent libvirtd remove empty task directory.