From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-mm@kvack.org
Subject: Re: [patch] mm, thp: drop page_table_lock to uncharge memcg pages
Date: Thu, 26 Apr 2012 16:39:22 -0700 [thread overview]
Message-ID: <20120426163922.4879dcb1.akpm@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1204261556100.15785@chino.kir.corp.google.com>
On Thu, 26 Apr 2012 15:57:30 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:
> mm->page_table_lock is hotly contested for page fault tests and isn't
> necessary to do mem_cgroup_uncharge_page() in do_huge_pmd_wp_page().
>
> ...
>
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -968,8 +968,10 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> spin_lock(&mm->page_table_lock);
> put_page(page);
> if (unlikely(!pmd_same(*pmd, orig_pmd))) {
> + spin_unlock(&mm->page_table_lock);
> mem_cgroup_uncharge_page(new_page);
> put_page(new_page);
> + goto out;
> } else {
> pmd_t entry;
> VM_BUG_ON(!PageHead(page));
But this is on the basically-never-happens race path and will surely have no
measurable benefit?
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next prev parent reply other threads:[~2012-04-26 23:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-26 22:57 [patch] mm, thp: drop page_table_lock to uncharge memcg pages David Rientjes
2012-04-26 23:39 ` Andrew Morton [this message]
2012-04-26 23:44 ` David Rientjes
2012-04-27 19:00 ` Andrea Arcangeli
2012-04-26 23:57 ` Johannes Weiner
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