From: Catalin Marinas <catalin.marinas@arm.com>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/10] mm/slab: Allow dynamic kmalloc() minimum alignment
Date: Thu, 7 Apr 2022 10:35:04 +0100 [thread overview]
Message-ID: <Yk6wSNz38Bv1lrmB@arm.com> (raw)
In-Reply-To: <Yk6sWNBSwNRbLdfZ@hyeyoo>
On Thu, Apr 07, 2022 at 06:18:16PM +0900, Hyeonggon Yoo wrote:
> On Thu, Apr 07, 2022 at 09:50:23AM +0100, Catalin Marinas wrote:
> > On Thu, Apr 07, 2022 at 03:46:37AM +0000, Hyeonggon Yoo wrote:
> > > On Tue, Apr 05, 2022 at 02:57:56PM +0100, Catalin Marinas wrote:
> > > > --- a/mm/slab_common.c
> > > > +++ b/mm/slab_common.c
> > > > @@ -838,9 +838,18 @@ void __init setup_kmalloc_cache_index_table(void)
> > > > }
> > > > }
> > > >
> > > > -static void __init
> > > > +unsigned int __weak arch_kmalloc_minalign(void)
> > > > +{
> > > > + return ARCH_KMALLOC_MINALIGN;
> > > > +}
> > > > +
> > >
> > > As ARCH_KMALLOC_ALIGN and arch_kmalloc_minalign() may not be same after
> > > patch 10, I think s/ARCH_KMALLOC_ALIGN/arch_kmalloc_minalign/g
> > > for every user of it would be more correct?
> >
> > Not if the code currently using ARCH_KMALLOC_MINALIGN needs a constant.
> > Yes, there probably are a few places where the code can cope with a
> > dynamic arch_kmalloc_minalign() but there are two other cases where a
> > constant is needed:
> >
> > 1. As a BUILD_BUG check because the code is storing some flags in the
> > bottom bits of a pointer. A smaller ARCH_KMALLOC_MINALIGN works just
> > fine here.
> >
> > 2. As a static alignment for DMA requirements. That's where the newly
> > exposed ARCH_DMA_MINALIGN should be used.
> >
> > Note that this series doesn't make the situation any worse than before
> > since ARCH_DMA_MINALIGN stays at 128 bytes for arm64. Current users can
> > evolve to use a dynamic alignment in future patches. My main aim with
> > this series is to be able to create kmalloc-64 caches on arm64.
>
> AFAIK there are bunch of drivers that directly calls kmalloc().
Well, lots of drivers call kmalloc() ;).
> It becomes tricky when e.g.) a driver allocates just 32 bytes,
> but architecture requires it to be 128-byte aligned.
That's the current behaviour, a 32 byte allocation would return an
object from kmalloc-128. I want to reduce this to at least kmalloc-64
(or smaller) if the CPU/SoC allows it.
> That's why everything allocated from kmalloc() need to be aligned in
> ARCH_DMA_MINALIGN.
I don't get your conclusion here. Would you mind explaining?
> So I'm yet skeptical on decoupling ARCH_DMA/KMALLOC_MINALIGN. Instead
> of decoupling it, I'm more into dynamically decreasing it.
The reason for decoupling is mostly that there are some static uses of
ARCH_KMALLOC_MINALIGN as per point 1 above. The other is the
__assume_kmalloc_alignment attribute. We shouldn't have such assumed
alignment larger than what a dynamic kmalloc() would return. To me it
makes a lot more sense for ARCH_KMALLOC_MINALIGN to be the minimum
guaranteed in a kernel build but kmalloc() returning a larger alignment
at run-time than the other way around.
Thanks.
--
Catalin
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next prev parent reply other threads:[~2022-04-07 9:55 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-05 13:57 [PATCH 00/10] mm, arm64: Reduce ARCH_KMALLOC_MINALIGN below the cache line size Catalin Marinas
2022-04-05 13:57 ` [PATCH 01/10] mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN Catalin Marinas
2022-04-05 23:59 ` Hyeonggon Yoo
2022-04-06 7:29 ` Arnd Bergmann
2022-04-06 12:09 ` Hyeonggon Yoo
2022-04-06 8:53 ` Catalin Marinas
2022-04-08 6:42 ` Hyeonggon Yoo
2022-04-08 9:06 ` Hyeonggon Yoo
2022-04-08 9:11 ` Catalin Marinas
2022-04-11 10:37 ` Hyeonggon Yoo
2022-04-11 14:02 ` Catalin Marinas
2022-04-05 13:57 ` [PATCH 02/10] drivers/base: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Catalin Marinas
2022-04-11 14:57 ` Andy Shevchenko
2022-04-11 17:39 ` Catalin Marinas
2022-04-05 13:57 ` [PATCH 03/10] drivers/gpu: " Catalin Marinas
2022-04-05 13:57 ` [PATCH 04/10] drivers/md: " Catalin Marinas
2022-04-05 13:57 ` [PATCH 05/10] drivers/spi: " Catalin Marinas
2022-04-05 14:05 ` Mark Brown
2022-04-05 13:57 ` [PATCH 06/10] drivers/usb: " Catalin Marinas
2022-04-05 13:57 ` [PATCH 07/10] crypto: " Catalin Marinas
2022-04-05 22:57 ` Herbert Xu
2022-04-06 6:53 ` Ard Biesheuvel
2022-04-06 8:49 ` Catalin Marinas
2022-04-06 9:41 ` Ard Biesheuvel
2022-04-07 4:30 ` Herbert Xu
2022-04-07 11:01 ` Catalin Marinas
2022-04-07 11:40 ` Herbert Xu
2022-04-07 16:28 ` Catalin Marinas
2022-04-08 3:25 ` Herbert Xu
2022-04-08 9:04 ` Catalin Marinas
2022-04-08 9:11 ` Herbert Xu
2022-04-12 9:32 ` Catalin Marinas
2022-04-12 9:40 ` Herbert Xu
2022-04-12 10:02 ` Catalin Marinas
2022-04-12 10:18 ` Herbert Xu
2022-04-12 12:31 ` Catalin Marinas
2022-04-12 22:01 ` Ard Biesheuvel
2022-04-13 8:47 ` Catalin Marinas
2022-04-13 19:53 ` Linus Torvalds
2022-04-14 5:38 ` Greg Kroah-Hartman
2022-04-14 13:52 ` Ard Biesheuvel
2022-04-14 14:27 ` Greg Kroah-Hartman
2022-04-14 14:36 ` Ard Biesheuvel
2022-04-14 14:52 ` Greg Kroah-Hartman
2022-04-14 15:01 ` Ard Biesheuvel
2022-04-14 15:10 ` Ard Biesheuvel
2022-04-14 19:49 ` Catalin Marinas
2022-04-14 22:25 ` Linus Torvalds
2022-04-15 6:03 ` Ard Biesheuvel
2022-04-15 11:09 ` Arnd Bergmann
2022-04-16 9:42 ` Catalin Marinas
2022-04-20 19:07 ` Catalin Marinas
2022-04-20 19:33 ` Linus Torvalds
2022-04-14 14:30 ` Ard Biesheuvel
2022-04-15 6:51 ` Herbert Xu
2022-04-15 7:49 ` Ard Biesheuvel
2022-04-15 7:51 ` Herbert Xu
2022-04-15 8:05 ` Ard Biesheuvel
2022-04-15 8:12 ` Herbert Xu
2022-04-15 9:51 ` Ard Biesheuvel
2022-04-15 10:04 ` Ard Biesheuvel
2022-04-15 10:12 ` Herbert Xu
2022-04-15 10:22 ` Ard Biesheuvel
2022-04-15 10:45 ` Herbert Xu
2022-04-15 11:38 ` Ard Biesheuvel
2022-04-17 8:08 ` Herbert Xu
2022-04-17 8:31 ` Catalin Marinas
2022-04-17 8:35 ` Herbert Xu
2022-04-17 8:50 ` Catalin Marinas
2022-04-17 8:58 ` Herbert Xu
2022-04-17 16:30 ` Catalin Marinas
2022-04-18 8:37 ` Herbert Xu
2022-04-18 9:19 ` Catalin Marinas
2022-04-18 16:44 ` Catalin Marinas
2022-04-19 21:50 ` Ard Biesheuvel
2022-04-20 10:36 ` Catalin Marinas
2022-04-20 11:29 ` Arnd Bergmann
2022-04-21 7:20 ` Christoph Hellwig
2022-04-21 7:36 ` Arnd Bergmann
2022-04-21 7:44 ` Christoph Hellwig
2022-04-21 8:05 ` Ard Biesheuvel
2022-04-21 11:06 ` Catalin Marinas
2022-04-21 12:28 ` Arnd Bergmann
2022-04-21 13:25 ` Catalin Marinas
2022-04-21 13:47 ` Arnd Bergmann
2022-04-21 14:44 ` Catalin Marinas
2022-04-21 14:47 ` Arnd Bergmann
2022-05-10 11:03 ` [RFC PATCH 0/7] crypto: Add helpers for allocating with DMA alignment Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 1/7] crypto: Prepare to move crypto_tfm_ctx Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 2/7] crypto: api - Add crypto_tfm_ctx_dma Herbert Xu
2022-05-10 17:10 ` Catalin Marinas
2022-05-12 3:57 ` Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 3/7] crypto: aead - Add ctx helpers with DMA alignment Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 4/7] crypto: hash " Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 5/7] crypto: skcipher " Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 6/7] crypto: api - Increase MAX_ALGAPI_ALIGNMASK to 127 Herbert Xu
2022-05-10 11:07 ` [RFC PATCH 7/7] crypto: caam - Explicitly request DMA alignment Herbert Xu
2022-04-15 12:18 ` [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Catalin Marinas
2022-04-15 12:25 ` Ard Biesheuvel
2022-04-15 9:51 ` Catalin Marinas
2022-04-15 12:31 ` Catalin Marinas
2022-04-17 8:11 ` Herbert Xu
2022-04-17 8:38 ` Catalin Marinas
2022-04-17 8:43 ` Herbert Xu
2022-04-17 16:29 ` Catalin Marinas
2022-07-15 22:23 ` Isaac Manjarres
2022-07-16 3:25 ` Herbert Xu
2022-07-18 17:53 ` Catalin Marinas
2022-09-21 0:47 ` Isaac Manjarres
2022-09-30 18:32 ` Catalin Marinas
2022-09-30 19:35 ` Linus Torvalds
2022-10-01 22:29 ` Catalin Marinas
2022-10-02 17:00 ` Linus Torvalds
2022-10-02 22:08 ` Ard Biesheuvel
2022-10-02 22:24 ` Linus Torvalds
2022-10-03 17:39 ` Catalin Marinas
2022-10-12 17:45 ` Isaac Manjarres
2022-10-13 16:57 ` Catalin Marinas
2022-10-13 18:58 ` Saravana Kannan
2022-10-14 16:25 ` Catalin Marinas
2022-10-14 20:23 ` Saravana Kannan
2022-10-14 20:44 ` Linus Torvalds
2022-10-16 21:37 ` Catalin Marinas
2022-04-12 10:20 ` Catalin Marinas
2022-04-07 6:14 ` Muchun Song
2022-04-07 9:25 ` Catalin Marinas
2022-04-07 10:00 ` Muchun Song
2022-04-07 11:06 ` Catalin Marinas
2022-04-05 13:57 ` [PATCH 08/10] mm/slab: Allow dynamic kmalloc() minimum alignment Catalin Marinas
2022-04-07 3:46 ` Hyeonggon Yoo
2022-04-07 8:50 ` Catalin Marinas
2022-04-07 9:18 ` Hyeonggon Yoo
2022-04-07 9:35 ` Catalin Marinas [this message]
2022-04-07 12:26 ` Hyeonggon Yoo
2022-04-11 11:55 ` Hyeonggon Yoo
2022-04-05 13:57 ` [PATCH 09/10] mm/slab: Simplify create_kmalloc_cache() args and make it static Catalin Marinas
2022-04-05 13:57 ` [PATCH 10/10] arm64: Enable dynamic kmalloc() minimum alignment Catalin Marinas
2022-04-07 14:40 ` [PATCH 00/10] mm, arm64: Reduce ARCH_KMALLOC_MINALIGN below the cache line size Vlastimil Babka
2022-04-07 17:48 ` Catalin Marinas
2022-04-08 14:37 ` Vlastimil Babka
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