From: Mel Gorman <mgorman@suse.de>
To: Weijie Yang <weijie.yang.kh@gmail.com>
Cc: Weijie Yang <weijie.yang@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@redhat.com>, Linux-MM <linux-mm@kvack.org>,
Linux-Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check
Date: Wed, 10 Dec 2014 14:03:44 +0000 [thread overview]
Message-ID: <20141210140344.GF21903@suse.de> (raw)
In-Reply-To: <CAL1ERfOxEJGJjZk9O_NKV82mOT+udto0tL2eCagicLig6CaJ=g@mail.gmail.com>
On Wed, Dec 10, 2014 at 09:38:42PM +0800, Weijie Yang wrote:
> On Tue, Dec 9, 2014 at 5:59 PM, Mel Gorman <mgorman@suse.de> wrote:
> > On Tue, Dec 09, 2014 at 03:40:35PM +0800, Weijie Yang wrote:
> >> If the free page and its buddy has different zone id, the current
> >> zone->lock cann't prevent buddy page getting allocated, this could
> >> trigger VM_BUG_ON_PAGE in a very tiny chance:
> >>
> >
> > Under what circumstances can a buddy page be allocated without the
> > zone->lock? Any parallel allocation from that zone that takes place will
> > be from the per-cpu allocator and should not be affected by this. Have
> > you actually hit this race?
>
> My description maybe not clear, if the free page and its buddy is not
> at the same zone, the holding zone->lock cann't prevent buddy page
> getting allocated.
You're right, the description is not clear but now I see your
point. Thanks.
Acked-by: Mel Gorman <mgorman@suse.de>
--
Mel Gorman
SUSE Labs
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WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de>
To: Weijie Yang <weijie.yang.kh@gmail.com>
Cc: Weijie Yang <weijie.yang@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@redhat.com>, Linux-MM <linux-mm@kvack.org>,
Linux-Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check
Date: Wed, 10 Dec 2014 14:03:44 +0000 [thread overview]
Message-ID: <20141210140344.GF21903@suse.de> (raw)
In-Reply-To: <CAL1ERfOxEJGJjZk9O_NKV82mOT+udto0tL2eCagicLig6CaJ=g@mail.gmail.com>
On Wed, Dec 10, 2014 at 09:38:42PM +0800, Weijie Yang wrote:
> On Tue, Dec 9, 2014 at 5:59 PM, Mel Gorman <mgorman@suse.de> wrote:
> > On Tue, Dec 09, 2014 at 03:40:35PM +0800, Weijie Yang wrote:
> >> If the free page and its buddy has different zone id, the current
> >> zone->lock cann't prevent buddy page getting allocated, this could
> >> trigger VM_BUG_ON_PAGE in a very tiny chance:
> >>
> >
> > Under what circumstances can a buddy page be allocated without the
> > zone->lock? Any parallel allocation from that zone that takes place will
> > be from the per-cpu allocator and should not be affected by this. Have
> > you actually hit this race?
>
> My description maybe not clear, if the free page and its buddy is not
> at the same zone, the holding zone->lock cann't prevent buddy page
> getting allocated.
You're right, the description is not clear but now I see your
point. Thanks.
Acked-by: Mel Gorman <mgorman@suse.de>
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2014-12-10 14:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-09 7:40 [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check Weijie Yang
2014-12-09 7:40 ` Weijie Yang
2014-12-09 9:59 ` Mel Gorman
2014-12-09 9:59 ` Mel Gorman
2014-12-10 13:38 ` Weijie Yang
2014-12-10 13:38 ` Weijie Yang
2014-12-10 14:03 ` Mel Gorman [this message]
2014-12-10 14:03 ` Mel Gorman
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