From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
Subject: Re: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name()
Date: Fri, 22 Mar 2013 10:48:32 +0100
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To: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Cc: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>

On Fri 22-03-13 13:41:40, Glauber Costa wrote:
> On 03/22/2013 01:31 PM, Michal Hocko wrote:
> > On Fri 22-03-13 12:22:23, Glauber Costa wrote:
> >> On 03/22/2013 12:17 PM, Li Zefan wrote:
> >>>> GFP_TEMPORARY groups short lived allocations but the mem cache is not
> >>>>> an ideal candidate of this type of allocations..
> >>>>>
> >>> I'm not sure I'm following you...
> >>>
> >>> char *memcg_cache_name()
> >>> {
> >>> 	char *name = alloc();
> >>> 	return name;
> >>> }
> >>>
> >>> kmem_cache_dup()
> >>> {
> >>> 	name = memcg_cache_name();
> >>> 	kmem_cache_create_memcg(name);
> >>> 	free(name);
> >>> }
> >>>
> >>> Isn't this a short lived allocation?
> >>>
> >>
> >> Hi,
> >>
> >> Thanks for identifying and fixing this.
> >>
> >> Li is right. The cache name will live long, but this is because the
> >> slab/slub caches will strdup it internally. So the actual memcg
> >> allocation is short lived.
> > 
> > OK, I have totally missed that. Sorry about the confusion. Then all the
> > churn around the allocation is pointless, no?
> > What about:
> 
> If we're really not concerned about stack, then yes. Even if always
> running from workqueues, a PAGE_SIZEd stack variable seems risky to me.

This is not on stack. It is static

-- 
Michal Hocko
SUSE Labs