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Message-ID: <20130804082509.GC24005@dhcp22.suse.cz>
Date: Sun, 4 Aug 2013 10:25:09 +0200
From: Michal Hocko <mhocko@...e.cz>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Al Viro <viro@...iv.linux.org.uk>,
Hugh Dickins <hughd@...gle.com>,
Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
Andi Kleen <ak@...ux.intel.com>,
Matthew Wilcox <willy@...ux.intel.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
Ning Qu <quning@...gle.com>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 02/23] memcg, thp: charge huge cache pages
On Sun 04-08-13 05:17:04, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
>
> mem_cgroup_cache_charge() has check for PageCompound(). The check
> prevents charging huge cache pages.
>
> I don't see a reason why the check is present. Looks like it's just
> legacy (introduced in 52d4b9a memcg: allocate all page_cgroup at boot).
>
> Let's just drop it.
If the page cache charging path only sees THP as compound pages then OK.
Can we keep at least VM_BUG_ON(PageCompound(page) && !PageTransHuge(page))
Otherwise mem_cgroup_charge_common would be confused and charge such a
page as order-0
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Other than that, looks good to me.
Acked-by: Michal Hocko <mhocko@...e.cz>
> ---
> mm/memcontrol.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b6cd870..dc50c1a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3921,8 +3921,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
>
> if (mem_cgroup_disabled())
> return 0;
> - if (PageCompound(page))
> - return 0;
>
> if (!PageSwapCache(page))
> ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
> --
> 1.8.3.2
>
--
Michal Hocko
SUSE Labs
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