Joonsoo,
On Mon, Sep 29, 2014 at 04:44:18PM +0900, Joonsoo Kim wrote:
> On Sat, Sep 27, 2014 at 11:24:49PM -0700, Jeremiah Mahler wrote:
> > On Thu, Aug 21, 2014 at 05:11:13PM +0900, Joonsoo Kim wrote:
> > > Because of chicken and egg problem, initializaion of SLAB is really
> > > complicated. We need to allocate cpu cache through SLAB to make
> > > the kmem_cache works, but, before initialization of kmem_cache,
> > > allocation through SLAB is impossible.
> > >
> > > On the other hand, SLUB does initialization with more simple way. It
> > > uses percpu allocator to allocate cpu cache so there is no chicken and
> > > egg problem.
> > >
> > > So, this patch try to use percpu allocator in SLAB. This simplify
> > > initialization step in SLAB so that we could maintain SLAB code more
> > > easily.
> > >
> > > From my testing, there is no performance difference.
> > >
> > > Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
> >
> > I just encountered a problem on a Lenovo Carbon X1 where it will
> > suspend but won't resume. A bisect indicated that this patch
> > is causing the problem.
> >
> > 997888488ef92da365b870247de773255227ce1f
> >
> > I imagine the patch author, Joonsoo Kim, might have a better idea
> > why this is happening than I do. But if I can provide any information
> > or run any tests that might be of help just let me know.
>
> Hello,
>
> Yeah, there is a bug. Below will fix your issue.
> Could you test it and report the result?
>
> Thanks for reporting it.
>
> --------->8---------------
> From e03ed6cc554e038b86d7b3a72b89d94e9ea808ba Mon Sep 17 00:00:00 2001
> From: Joonsoo Kim <iamjoonsoo....@lge.com>
> Date: Mon, 29 Sep 2014 16:30:43 +0900
> Subject: [PATCH] mm/slab: fix cpu on/off handling
>
> When cpu off, we flush all cpu cached objects to it's own slab.
> free_block() is used for this purpose and it's role is just to flush
> objects from array_cache to proper slab. It doesn't adjust array_cache's
> internal fields so we should manually reset them to proper value.
> Without this fix, we maintain free objects duplicately, one is in
> cpu cache, and, the other one is in the slab. So system would be broken.
>
> Reported-by: Jeremiah Mahler <jmmah...@gmail.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
> ---
> mm/slab.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 1162f0e..ce289b4 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1102,8 +1102,10 @@ static void cpuup_canceled(long cpu)
>
> /* cpu is dead; no one can alloc from it. */
> nc = per_cpu_ptr(cachep->cpu_cache, cpu);
> - if (nc)
> + if (nc) {
> free_block(cachep, nc->entry, nc->avail, node, &list);
> + nc->avail = 0;
> + }
>
> if (!cpumask_empty(mask)) {
> spin_unlock_irq(&n->list_lock);
> --
> 1.7.9.5
>
That fixed the problem. Thanks!
Tested-by: Jeremiah Mahler <jmmah...@gmail.com>
--
Jeremiah Mahler
jmmah...@gmail.com
http://github.com/jmahler
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