lkml.org 
[lkml]   [2014]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [REGRESSION] [FIXED] [PATCH 1/3] mm/slab: use percpu allocator for cpu cache
On Mon, Sep 29, 2014 at 10:03:15AM -0700, Jeremiah Mahler wrote:
> 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.kim@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.kim@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 <jmmahler@gmail.com>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@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 <jmmahler@gmail.com>

Good!

Thanks.


\
 
 \ /
  Last update: 2014-10-02 08:01    [W:0.048 / U:0.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site