From: Andrew Morton <akpm@linux-foundation.org>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>, azurIt <azurit@pobox.sk>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org,
Christian Casteyde <casteyde.christian@free.fr>,
Pekka Enberg <penberg@kernel.org>,
Christoph Lameter <cl@linux.com>
Subject: Re: [patch 2/2] fs: buffer: move allocation failure loop into the allocator
Date: Tue, 3 Dec 2013 18:07:17 -0800 [thread overview]
Message-ID: <20131203180717.94c013d1.akpm@linux-foundation.org> (raw)
In-Reply-To: <20131204015218.GA19709@lge.com>
On Wed, 4 Dec 2013 10:52:18 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> SLUB already try to allocate high order page with clearing __GFP_NOFAIL.
> But, when allocating shadow page for kmemcheck, it missed clearing
> the flag. This trigger WARN_ON_ONCE() reported by Christian Casteyde.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=65991
>
> This patch fix this situation by using same allocation flag as original
> allocation.
>
> Reported-by: Christian Casteyde <casteyde.christian@free.fr>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 545a170..3dd28b1 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1335,11 +1335,12 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
> page = alloc_slab_page(alloc_gfp, node, oo);
> if (unlikely(!page)) {
> oo = s->min;
What is the value of s->min? Please tell me it's zero.
> + alloc_gfp = flags;
> /*
> * Allocation may have failed due to fragmentation.
> * Try a lower order alloc if possible
> */
> - page = alloc_slab_page(flags, node, oo);
> + page = alloc_slab_page(alloc_gfp, node, oo);
>
> if (page)
> stat(s, ORDER_FALLBACK);
This change doesn't actually do anything.
> @@ -1349,7 +1350,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
> && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
> int pages = 1 << oo_order(oo);
>
> - kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);
> + kmemcheck_alloc_shadow(page, oo_order(oo), alloc_gfp, node);
That seems reasonable, assuming kmemcheck can handle the allocation
failure.
Still I dislike this practice of using unnecessarily large allocations.
What does it gain us? Slightly improved object packing density.
Anything else?
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next prev parent reply other threads:[~2013-12-04 2:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-08 20:58 [patch 1/2] mm: memcg: handle non-error OOM situations more gracefully Johannes Weiner
2013-10-08 20:58 ` [patch 2/2] fs: buffer: move allocation failure loop into the allocator Johannes Weiner
2013-10-11 20:51 ` Andrew Morton
2013-12-04 0:59 ` Andrew Morton
2013-12-04 1:52 ` Joonsoo Kim
2013-12-04 2:07 ` Andrew Morton [this message]
2013-12-04 2:42 ` Joonsoo Kim
2013-12-04 15:17 ` Christoph Lameter
2013-12-04 16:02 ` Joonsoo Kim
2013-12-04 16:33 ` Christoph Lameter
2013-12-05 8:44 ` Joonsoo Kim
2013-12-05 18:50 ` Christoph Lameter
2013-12-06 8:57 ` Joonsoo Kim
2013-12-13 6:58 ` Joonsoo Kim
2013-12-13 16:40 ` Christoph Lameter
2013-12-16 8:22 ` Joonsoo Kim
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