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Message-ID: <6599ad830803161902r8f9a274t246a25b3d337fee8@mail.gmail.com>
Date: Mon, 17 Mar 2008 10:02:09 +0800
From: "Paul Menage" <menage@...gle.com>
To: "Balbir Singh" <balbir@...ux.vnet.ibm.com>
Cc: linux-mm@...ck.org, "Hugh Dickins" <hugh@...itas.com>,
"Sudhir Kumar" <skumar@...ux.vnet.ibm.com>,
"YAMAMOTO Takashi" <yamamoto@...inux.co.jp>, lizf@...fujitsu.com,
linux-kernel@...r.kernel.org, taka@...inux.co.jp,
"David Rientjes" <rientjes@...gle.com>,
"Pavel Emelianov" <xemul@...nvz.org>,
"Andrew Morton" <akpm@...ux-foundation.org>,
"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC][2/3] Account and control virtual address space allocations
On Mon, Mar 17, 2008 at 1:30 AM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> /*
> + * Check if the current cgroup exceeds its address space limit.
> + * Returns 0 on success and 1 on failure.
> + */
> +int mem_cgroup_update_as(struct mm_struct *mm, long nr_pages)
> +{
> + int ret = 0;
> + struct mem_cgroup *mem;
> + if (mem_cgroup_subsys.disabled)
> + return ret;
> +
> + rcu_read_lock();
> + mem = rcu_dereference(mm->mem_cgroup);
> + css_get(&mem->css);
> + rcu_read_unlock();
> +
How about if this function avoided charging the root cgroup? You'd
save 4 atomic operations on a global data structure on every
mmap/munmap when the virtual address limit cgroup wasn't in use, which
could be significant on a large system. And I don't see situations
where you really need to limit the address space of the root cgroup.
Paul
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