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From: Shakeel Butt <shakeelb@google.com>
To: Christopher Lameter <cl@linux.com>, Roman Gushchin <guro@fb.com>
Cc: Yu Zhao <yuzhao@google.com>, Pekka Enberg <penberg@kernel.org>,
	 David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Linux MM <linux-mm@kvack.org>,
	 LKML <linux-kernel@vger.kernel.org>,
	 "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock
Date: Mon, 11 Nov 2019 10:15:20 -0800
Message-ID: <CALvZod7sdWpkERPbU9sram2q7PubS4yvkzVibRf+4bPKT1v4XQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1911111543420.10669@www.lameter.com>

+Roman Gushchin

On Mon, Nov 11, 2019 at 7:47 AM Christopher Lameter <cl@linux.com> wrote:
>
> On Sun, 10 Nov 2019, Yu Zhao wrote:
>
> > On Sat, Nov 09, 2019 at 11:16:28PM +0000, Christopher Lameter wrote:
> > > On Sat, 9 Nov 2019, Yu Zhao wrote:
> > >
> > > > >         struct page *page, *h;
> > > > > +       unsigned long *map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
> > > > > +
> > > > > +       if (!map)
> > > > > +               return;
> > > >
> > > > What would happen if we are trying to allocate from the slab that is
> > > > being shut down? And shouldn't the allocation be conditional (i.e.,
> > > > only when CONFIG_SLUB_DEBUG=y)?
> > >
> > > Kmalloc slabs are never shut down.
> >
> > Maybe I'm not thinking straight -- isn't it what caused the deadlock in
> > the first place?
>
> Well if kmalloc allocations become a problem then we have numerous
> issues all over the kernel to fix.
>
> > Kmalloc slabs can be shut down when memcg is on.
>
> Kmalloc needs to work even during shutdown of a memcg.
>
> Maybe we need to fix memcg to not allocate from the current memcg during
> shutdown?
>
>

Roman recently added reparenting of memcg kmem caches on memcg offline
and can comment in more detail but we don't shutdown a kmem cache
until all the in-fly memcg allocations are resolved. Also the
allocation here does not look like a __GFP_ACCOUNT allocation.


  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  6:10 [PATCH] " Yu Zhao
2019-09-09 16:00 ` Kirill A. Shutemov
     [not found]   ` <e5e25aa3-651d-92b4-ac82-c5011c66a7cb@I-love.SAKURA.ne.jp>
2019-09-09 21:39     ` Yu Zhao
     [not found]       ` <201909100141.x8A1fVdu048305@www262.sakura.ne.jp>
2019-09-10  2:16         ` Yu Zhao
2019-09-10  9:16       ` Kirill A. Shutemov
2019-09-11 14:13 ` Andrew Morton
2019-09-12  0:29   ` [PATCH 1/3] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  0:29     ` [PATCH 2/3] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12  0:44       ` Kirill A. Shutemov
2019-09-12  1:31         ` Yu Zhao
2019-09-12  2:31         ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  2:31           ` [PATCH v2 2/4] mm: clean up validate_slab() Yu Zhao
2019-09-12  9:46             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 3/4] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12 10:04             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 4/4] mm: lock slub page when listing objects Yu Zhao
2019-09-12 10:06             ` Kirill A. Shutemov
2019-09-12 21:12               ` Yu Zhao
2019-09-13 14:58             ` Christopher Lameter
2019-09-12  9:40           ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Kirill A. Shutemov
2019-09-12 21:11             ` Yu Zhao
2019-09-12 22:03               ` Kirill A. Shutemov
2019-09-14  0:07           ` [PATCH v3 1/2] mm: clean up validate_slab() Yu Zhao
2019-09-14  0:07             ` [PATCH v3 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-16  8:39             ` [PATCH v3 1/2] mm: clean up validate_slab() Kirill A. Shutemov
2019-11-08 19:39             ` [PATCH v4 " Yu Zhao
2019-11-08 19:39               ` [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-11-09 20:52                 ` Christopher Lameter
2019-11-09 23:01                   ` Yu Zhao
2019-11-09 23:16                     ` Christopher Lameter
2019-11-10 18:47                       ` Yu Zhao
2019-11-11 15:47                         ` Christopher Lameter
2019-11-11 15:55                           ` [FIX] slub: Remove kmalloc under list_lock from list_slab_objects() V2 Christopher Lameter
2019-11-30 23:09                             ` Andrew Morton
2019-12-02 15:12                               ` Christopher Lameter
2019-12-07 22:03                                 ` Yu Zhao
2019-11-11 18:15                           ` Shakeel Butt [this message]
2019-09-12  0:29     ` [PATCH 3/3] mm: lock slub page when listing objects Yu Zhao

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