From: Alexey Dobriyan <adobriyan@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christopher Lameter <cl@linux.com>,
penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
linux-mm@kvack.org
Subject: Re: [PATCH 23/25] slub: make struct kmem_cache_order_objects::x unsigned int
Date: Fri, 6 Apr 2018 21:02:20 +0300 [thread overview]
Message-ID: <20180406180220.GA32149@avx2> (raw)
In-Reply-To: <20180405145108.e1a9f788bea329653505cadc@linux-foundation.org>
On Thu, Apr 05, 2018 at 02:51:08PM -0700, Andrew Morton wrote:
> On Tue, 6 Mar 2018 12:51:47 -0600 (CST) Christopher Lameter <cl@linux.com> wrote:
>
> > On Mon, 5 Mar 2018, Alexey Dobriyan wrote:
> >
> > > struct kmem_cache_order_objects is for mixing order and number of objects,
> > > and orders aren't bit enough to warrant 64-bit width.
> > >
> > > Propagate unsignedness down so that everything fits.
> > >
> > > !!! Patch assumes that "PAGE_SIZE << order" doesn't overflow. !!!
> >
> > PAGE_SIZE could be a couple of megs on some platforms (256 or so on
> > Itanium/PowerPC???) . So what are the worst case scenarios here?
> >
> > I think both order and # object should fit in a 32 bit number.
> >
> > A page with 256M size and 4 byte objects would have 64M objects.
>
> Another dangling review comment. Alexey, please respond?
PowerPC is 256KB, IA64 is 64KB.
So "PAGE_SIZE << order" overflows if order is 14 (or 13 if signed int
slips in somewhere. Highest safe order is 12, which should be enough.
When was the last time you saw 2GB slab?
It never happenes as costly order is 3(?).
next prev parent reply other threads:[~2018-04-06 18:02 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-05 20:07 [PATCH 01/25] slab: fixup calculate_alignment() argument type Alexey Dobriyan
2018-03-05 20:07 ` [PATCH 02/25] slab: make kmalloc_index() return "unsigned int" Alexey Dobriyan
2018-03-06 18:24 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 03/25] slab: make kmalloc_size() " Alexey Dobriyan
2018-03-06 18:24 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 04/25] slab: make create_kmalloc_cache() work with 32-bit sizes Alexey Dobriyan
2018-03-06 18:32 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 05/25] slab: make create_boot_cache() " Alexey Dobriyan
2018-03-06 18:34 ` Christopher Lameter
2018-03-06 19:14 ` Matthew Wilcox
2018-03-05 20:07 ` [PATCH 06/25] slab: make kmem_cache_create() " Alexey Dobriyan
2018-03-06 18:37 ` Christopher Lameter
2018-04-05 21:48 ` Andrew Morton
2018-04-06 8:40 ` Alexey Dobriyan
2018-04-07 15:13 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 07/25] slab: make size_index[] array u8 Alexey Dobriyan
2018-03-06 18:38 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 08/25] slab: make size_index_elem() unsigned int Alexey Dobriyan
2018-03-06 18:39 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 09/25] slub: make ->remote_node_defrag_ratio " Alexey Dobriyan
2018-03-06 18:41 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 10/25] slub: make ->max_attr_size " Alexey Dobriyan
2018-03-06 18:42 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 11/25] slub: make ->red_left_pad " Alexey Dobriyan
2018-03-06 18:42 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 12/25] slub: make ->reserved " Alexey Dobriyan
2018-03-06 18:43 ` Christopher Lameter
2018-03-09 15:51 ` Alexey Dobriyan
2018-03-06 18:45 ` Matthew Wilcox
2018-03-09 22:42 ` Alexey Dobriyan
2018-03-05 20:07 ` [PATCH 13/25] slub: make ->align " Alexey Dobriyan
2018-03-06 18:43 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 14/25] slub: make ->inuse " Alexey Dobriyan
2018-03-06 18:44 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 15/25] slub: make ->cpu_partial " Alexey Dobriyan
2018-03-06 18:44 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 16/25] slub: make ->offset " Alexey Dobriyan
2018-03-06 18:45 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 17/25] slub: make ->object_size " Alexey Dobriyan
2018-03-06 18:45 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 18/25] slub: make ->size " Alexey Dobriyan
2018-03-06 18:46 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 19/25] slab: make kmem_cache_flags accept 32-bit object size Alexey Dobriyan
2018-03-06 18:47 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 20/25] kasan: make kasan_cache_create() work with 32-bit slab cache sizes Alexey Dobriyan
2018-03-05 20:07 ` [PATCH 21/25] slab: make usercopy region 32-bit Alexey Dobriyan
2018-03-05 20:07 ` [PATCH 22/25] slub: make slab_index() return unsigned int Alexey Dobriyan
2018-03-06 18:48 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 23/25] slub: make struct kmem_cache_order_objects::x " Alexey Dobriyan
2018-03-06 18:51 ` Christopher Lameter
2018-04-05 21:51 ` Andrew Morton
2018-04-06 18:02 ` Alexey Dobriyan [this message]
2018-04-07 15:18 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 24/25] slub: make size_from_object() return " Alexey Dobriyan
2018-03-06 18:52 ` Christopher Lameter
2018-03-05 20:07 ` [PATCH 25/25] slab: use 32-bit arithmetic in freelist_randomize() Alexey Dobriyan
2018-03-06 18:52 ` Christopher Lameter
2018-03-06 18:21 ` [PATCH 01/25] slab: fixup calculate_alignment() argument type Christopher Lameter
2018-04-10 20:25 ` Matthew Wilcox
2018-04-10 20:47 ` Alexey Dobriyan
2018-04-10 21:02 ` Matthew Wilcox
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