From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Feng Tang <feng.tang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Dmitry Vyukov <dvyukov@google.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
John Garry <john.garry@huawei.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: Re: [PATCH v4 1/4] mm/slub: enable debugging memory wasting of kmalloc
Date: Thu, 1 Sep 2022 20:14:40 +0900 [thread overview]
Message-ID: <YxCUIM4BWVZD6fnk@hyeyoo> (raw)
In-Reply-To: <YxA9etTqGsaogfZ6@feng-clx>
On Thu, Sep 01, 2022 at 01:04:58PM +0800, Feng Tang wrote:
> On Wed, Aug 31, 2022 at 10:52:15PM +0800, Hyeonggon Yoo wrote:
> > On Mon, Aug 29, 2022 at 03:56:15PM +0800, Feng Tang wrote:
> > > kmalloc's API family is critical for mm, with one nature that it will
> > > round up the request size to a fixed one (mostly power of 2). Say
> > > when user requests memory for '2^n + 1' bytes, actually 2^(n+1) bytes
> > > could be allocated, so in worst case, there is around 50% memory
> > > space waste.
> > >
> >
> > [...]
> >
> > > static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
> > > - unsigned long addr, struct kmem_cache_cpu *c)
> > > + unsigned long addr, struct kmem_cache_cpu *c, unsigned int orig_size)
> > > {
> > > void *freelist;
> > > struct slab *slab;
> > > @@ -3115,6 +3158,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
> > >
> > > if (s->flags & SLAB_STORE_USER)
> > > set_track(s, freelist, TRACK_ALLOC, addr);
> > > + set_orig_size(s, freelist, orig_size);
> > >
> > > return freelist;
> > > }
> > > @@ -3140,6 +3184,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
> > > */
> > > if (s->flags & SLAB_STORE_USER)
> > > set_track(s, freelist, TRACK_ALLOC, addr);
> > > + set_orig_size(s, freelist, orig_size);
> > > +
> > > return freelist;
> > > }
> >
> > Maybe we can move set_track() and set_orig_size() to after slab_post_alloc_hook().
> > something like alloc/free hooks for debugging caches? (and drop orig_size parameter.)
>
> Yep, we discussed this during v3 review
> https://lore.kernel.org/lkml/442d2b9c-9f07-8954-b90e-b4a9f8b64303@intel.com/
Ah, I missed that :) Thanks!
Considering the added cost (should be low) and races with validation,
I think this approach will cost more than it get. Sorry for the noise.
p.s. I think I can review this series in few days.
Thanks for your efforts!
> Will revisit this considering recent refactoring and the following
> kmalloc data redzone patches.
> Thanks,
> Feng
>
> > Thanks!
--
Thanks,
Hyeonggon
next prev parent reply other threads:[~2022-09-01 11:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-29 7:56 [PATCH v4 0/4] mm/slub: some debug enhancements for kmalloc objects Feng Tang
2022-08-29 7:56 ` [PATCH v4 1/4] mm/slub: enable debugging memory wasting of kmalloc Feng Tang
2022-08-31 14:52 ` Hyeonggon Yoo
2022-09-01 5:04 ` Feng Tang
2022-09-01 11:14 ` Hyeonggon Yoo [this message]
2022-09-01 14:01 ` Hyeonggon Yoo
2022-09-02 6:15 ` Feng Tang
2022-09-04 9:03 ` Hyeonggon Yoo
2022-09-04 9:42 ` Feng Tang
2022-09-04 10:58 ` Hyeonggon Yoo
2022-09-05 2:55 ` Feng Tang
2022-09-05 6:29 ` Vlastimil Babka
2022-09-05 7:06 ` Feng Tang
2022-09-05 7:33 ` Vlastimil Babka
2022-09-05 8:37 ` Feng Tang
2022-09-06 13:39 ` Hyeonggon Yoo
2022-08-29 7:56 ` [PATCH v4 2/4] mm/slub: only zero the requested size of buffer for kzalloc Feng Tang
2022-08-29 7:56 ` [PATCH v4 3/4] mm: kasan: Add free_meta size info in struct kasan_cache Feng Tang
2022-08-29 7:56 ` [PATCH v4 4/4] mm/slub: extend redzone check to cover extra allocated kmalloc space than requested Feng Tang
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