[PATCH] cgroup: print pretty format in /proc/cgroups

[PATCH] cgroup: print pretty format in /proc/cgroups

[Jianyu Zhan]

I found that /proc/cgroups printed format has ugly alignment(see below).

This patch confines every field in fixed-width(16 actually) range.
Though MAX_CGROUP_TYPE_NAMELEN is 32, but currently no subsystem
has name width more than 10, so 16 is a moderate width; besides, 16
figures could accomandate enormous huge number, so no need to worry
that these fields would clobber each other.

Before:
  #subsys_name     hierarchy       num_cgroups     enabled
  cpuset	2	1	1
  cpu	3	1	1
  cpuacct	3	1	1
  memory	4	1	1
  devices	5	1	1
  freezer 6	1	1
  net_cls	7	1	1
  blkio	8	1	1
  perf_event	9	1	1
  hugetlb	10	1	1

Patch applied:
  #subsys_name     hierarchy       num_cgroups     enabled
  cpuset          2               1               1
  cpu             3               1               1
  cpuacct         3               1               1
  memory          4               1               1
  devices         5               1               1
  freezer         6               1               1
  net_cls         7               1               1
  blkio           8               1               1
  perf_event      9               1               1
  hugetlb         10              1               1

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
---
 kernel/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9fcdaa7..d981697 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4347,7 +4347,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
 	mutex_lock(&cgroup_mutex);
 
 	for_each_subsys(ss, i)
-		seq_printf(m, "%s\t%d\t%d\t%d\n",
+		seq_printf(m, "%-16s%-16d%-16d%-16d\n",
 			   ss->name, ss->root->hierarchy_id,
 			   atomic_read(&ss->root->nr_cgrps), !ss->disabled);
 
-- 
1.9.0.GIT

Re: [PATCH] cgroup: print pretty format in /proc/cgroups

[Tejun Heo]

On Tue, Apr 15, 2014 at 08:47:45PM +0800, Jianyu Zhan wrote:
> I found that /proc/cgroups printed format has ugly alignment(see below).
> 
> This patch confines every field in fixed-width(16 actually) range.
> Though MAX_CGROUP_TYPE_NAMELEN is 32, but currently no subsystem
> has name width more than 10, so 16 is a moderate width; besides, 16
> figures could accomandate enormous huge number, so no need to worry
> that these fields would clobber each other.

The problem there is that there could be programs / scripts parsing it
assuming single tab between entries.  It surely is ugly but do we
care?

Thanks.

-- 
tejun

Re: [PATCH] cgroup: print pretty format in /proc/cgroups

[Daniel P. Berrange]

On Tue, Apr 15, 2014 at 08:47:45PM +0800, Jianyu Zhan wrote:
> I found that /proc/cgroups printed format has ugly alignment(see below).

[snip]

> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 9fcdaa7..d981697 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -4347,7 +4347,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
>  	mutex_lock(&cgroup_mutex);
>  
>  	for_each_subsys(ss, i)
> -		seq_printf(m, "%s\t%d\t%d\t%d\n",
> +		seq_printf(m, "%-16s%-16d%-16d%-16d\n",
>  			   ss->name, ss->root->hierarchy_id,
>  			   atomic_read(&ss->root->nr_cgrps), !ss->disabled);

This is liable to break userspace apps which might currently parse the
file by splitting on '\t'

Regards,
Daniel
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Re: [PATCH] cgroup: print pretty format in /proc/cgroups

[Zhan Jianyu]

On Tue, Apr 15, 2014 at 8:51 PM, Tejun Heo <tj@kernel.org> wrote:
> The problem there is that there could be programs / scripts parsing it
> assuming single tab between entries.  It surely is ugly but do we
> care?

Oh, you are right. It is an exposed user interface. This will make lots of
administrator unhappy ;-(

Thanks,
Jianyu Zhan