On Mon, 2 Aug 2010 23:30:51 +0530 Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-07-29 13:27:03]: > > > On Thu, 29 Jul 2010 09:32:26 +0900 > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > On Wed, 28 Jul 2010 12:45:13 -0700 > > > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > My gut reaction to this sort of thing is "run away in terror". It > > > > encourages kernel developers to operate like lackadaisical userspace > > > > developers and to assume that underlying code can perform heroic and > > > > immortal feats. But it can't. This is the kernel and the kernel is a > > > > tough and hostile place and callers should be careful and defensive and > > > > take great efforts to minimise the strain they put upon other systems. > > > > > > > > IOW, can we avoid doing this? > > > > > > > > > > > I'll use pre-allocated pointer array in the next version. It's simple even > > if a bit slow. > > > > == > > struct mem_cgroup *mem_cgroups[CONFIG_MAX_MEM_CGROUPS] __read_mostly; > > #define id_to_memcg(id) mem_cgroups[id]; > > == > > Hmm.. I thought we were going to reuse css_id() and use that to get to > the cgroup. May be I am missing something. > ? lookup_css_id() requires multi-level table lookup because of radix-tree. And compiler can't generate an optimized code. linear table lookup is quick. -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>