Re: [PATCH] use vmalloc for mem_cgroup allocation. v2

From: Andrew Morton
Date: Mon Apr 14 2008 - 22:21:19 EST


On Tue, 15 Apr 2008 10:08:25 +0800 Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:

> > @@ -992,8 +993,10 @@ mem_cgroup_create(struct cgroup_subsys *
> > if (unlikely((cont->parent) == NULL)) {
> > mem = &init_mem_cgroup;
> > page_cgroup_cache = KMEM_CACHE(page_cgroup, SLAB_PANIC);
> > - } else
> > - mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
> > + } else {
> > + mem = vmalloc(sizeof(struct mem_cgroup));
> > + memset(mem, 0, sizeof(*mem));
>
> what if mem == NULL. ;)
>
> > + }
> >
> > if (mem == NULL)
> > return ERR_PTR(-ENOMEM);
>
> So we can move this NULL check to the above else branch, in the if brach,
> mem won't be NULL.

err, yes.

So I have:

if (unlikely((cont->parent) == NULL)) {
mem = &init_mem_cgroup;
page_cgroup_cache = KMEM_CACHE(page_cgroup, SLAB_PANIC);
} else {
mem = vmalloc(sizeof(struct mem_cgroup));
if (mem == NULL)
return ERR_PTR(-ENOMEM);
memset(mem, 0, sizeof(*mem));
}


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