Re: [PATCH] KVM: Create debugfs statistics for each VM

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 01/28/2016 04:49 PM, Janosch Frank wrote:
> KVM statistics for VMs (no. of exits, halts and other special
> instructions) are currently only available in a summarized manner for
> all VMs. They are exported to userland through files in the kvm
> debugfs directory and used for performance monitoring, as well as VM
> problem detection with helper tools like kvm_stat. If a VM has
> problems and therefore creates a large number of exits, one can not
> easily find out which one it is, as there is no VM specific data.
> 
> This patch adds a kvm debugfs subdirectory for each VM, which is named
> after its pid and file descriptor. They contain the same kind of files
> that are already in the kvm debugfs directory, but the data that is
> exported through them is now VM specific.
> 
> CC: Dan Carpenter <dan.carpenter@oracle.com> [includes fixes by Dan Carpenter]
> Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>

for s390:
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> 


some questions below

[...]
> 
> +/* Worst case buffer size needed for holding an integer. */
> +#define ITOA_MAX_LEN 12

4294967295 has 10, so this is to cover the \0 and a potential "-", correct?


[...]
> @@ -3436,7 +3602,8 @@ static int kvm_init_debug(void)
>  	if (kvm_debugfs_dir == NULL)
>  		goto out;
> 
> -	for (p = debugfs_entries; p->name; ++p) {
> +	kvm_debugfs_num_entries = 0;
> +	for (p = debugfs_entries; p->name; ++p, kvm_debugfs_num_entries++) {

Looks like we cannot use ARRAY_SIZE(kvm_stats_debugfs_item), so unless somebody
has a better idea we have to stick with kvm_debugfs_num_entries being calculated.


>  		if (!debugfs_create_file(p->name, 0444, kvm_debugfs_dir,
>  					 (void *)(long)p->offset,
>  					 stat_fops[p->kind]))
>