linux-kernel - Re: + slub-bulk-alloc-extract-objects-from-the-per-cpu-slab.patch added to -mm tree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Tue, 9 Jun 2015 09:09:56 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	linux-kernel@...r.kernel.org, cl@...ux.com, penberg@...nel.org,
	rientjes@...gle.com, mm-commits@...r.kernel.org, brouer@...hat.com
Subject: Re: + slub-bulk-alloc-extract-objects-from-the-per-cpu-slab.patch
 added to -mm tree

On Tue, 9 Jun 2015 09:26:39 +0900
Joonsoo Kim <iamjoonsoo.kim@....com> wrote:

> On Wed, Apr 08, 2015 at 03:53:13PM -0700, akpm@...ux-foundation.org wrote:
> > 
> > The patch titled
> >      Subject: slub bulk alloc: extract objects from the per cpu slab
> > has been added to the -mm tree.  Its filename is
> >      slub-bulk-alloc-extract-objects-from-the-per-cpu-slab.patch
> > 
> > This patch should soon appear at
> >     http://ozlabs.org/~akpm/mmots/broken-out/slub-bulk-alloc-extract-objects-from-the-per-cpu-slab.patch
> > and later at
> >     http://ozlabs.org/~akpm/mmotm/broken-out/slub-bulk-alloc-extract-objects-from-the-per-cpu-slab.patch
> > 
> > Before you just go and hit "reply", please:
> >    a) Consider who else should be cc'ed
> >    b) Prefer to cc a suitable mailing list as well
> >    c) Ideally: find the original patch on the mailing list and do a
> >       reply-to-all to that, adding suitable additional cc's
> > 
> > *** Remember to use Documentation/SubmitChecklist when testing your code ***
> > 
> > The -mm tree is included into linux-next and is updated
> > there every 3-4 working days
> > 
> > ------------------------------------------------------
> > From: Christoph Lameter <cl@...ux.com>
> > Subject: slub bulk alloc: extract objects from the per cpu slab
> > 
> > First piece: acceleration of retrieval of per cpu objects
> > 
> > If we are allocating lots of objects then it is advantageous to disable
> > interrupts and avoid the this_cpu_cmpxchg() operation to get these objects
> > faster.  Note that we cannot do the fast operation if debugging is
> > enabled.  Note also that the requirement of having interrupts disabled
> > avoids having to do processor flag operations.
> > 
> > Allocate as many objects as possible in the fast way and then fall back to
> > the generic implementation for the rest of the objects.
> > 
> > Signed-off-by: Christoph Lameter <cl@...ux.com>
> > Cc: Jesper Dangaard Brouer <brouer@...hat.com>
> > Cc: Christoph Lameter <cl@...ux.com>
> > Cc: Pekka Enberg <penberg@...nel.org>
> > Cc: David Rientjes <rientjes@...gle.com>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> > 
> >  mm/slub.c |   27 ++++++++++++++++++++++++++-
> >  1 file changed, 26 insertions(+), 1 deletion(-)
> > 
> > diff -puN mm/slub.c~slub-bulk-alloc-extract-objects-from-the-per-cpu-slab mm/slub.c
> > --- a/mm/slub.c~slub-bulk-alloc-extract-objects-from-the-per-cpu-slab
> > +++ a/mm/slub.c
> > @@ -2759,7 +2759,32 @@ EXPORT_SYMBOL(kmem_cache_free_bulk);
> >  bool kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> >  								void **p)
> >  {
> > -	return kmem_cache_alloc_bulk(s, flags, size, p);
> > +	if (!kmem_cache_debug(s)) {
> > +		struct kmem_cache_cpu *c;
> > +
> > +		/* Drain objects in the per cpu slab */
> > +		local_irq_disable();
> > +		c = this_cpu_ptr(s->cpu_slab);
> > +
> > +		while (size) {
> > +			void *object = c->freelist;
> > +
> > +			if (!object)
> > +				break;
> > +
> > +			c->freelist = get_freepointer(s, object);
> > +			*p++ = object;
> > +			size--;
> > +
> > +			if (unlikely(flags & __GFP_ZERO))
> > +				memset(object, 0, s->object_size);
> > +		}
> > +		c->tid = next_tid(c->tid);
> > +
> > +		local_irq_enable();
> > +	}
> > +
> > +	return __kmem_cache_alloc_bulk(s, flags, size, p);
> 
> Hello,
> 
> So, if __kmem_cache_alloc_bulk() fails, all allocated objects in array
> should be freed, but, __kmem_cache_alloc_bulk() can't know
> about objects allocated by this slub specific kmem_cache_alloc_bulk()
> function. Please fix it.

Check, I've already noticed this, and have fixed it in my local git
tree. 

How do I submit a fix to AKPM? (do I replace the commit/patch, or do I
apply a patch on top)

(And as you also noticed, I've also moved the memset out of the loop,
after irq_enable)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/