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

[Eli Qiao]

--  
Best regards  
Eli

天涯无处不重逢
a leaf duckweed belongs to the sea, where not to meet in life  

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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.

  

   

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