From: Catalin Marinas <catalin.marinas@arm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>,
Ard Biesheuvel <ardb@kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
Date: Thu, 21 Apr 2022 15:44:08 +0100 [thread overview]
Message-ID: <YmFtuJmdMZcsoWnO@arm.com> (raw)
In-Reply-To: <CAK8P3a28NuZE628f1Bga_-gGSpHnPFx=2cBW0oDW4MFAzCSb+w@mail.gmail.com>
On Thu, Apr 21, 2022 at 03:47:30PM +0200, Arnd Bergmann wrote:
> On Thu, Apr 21, 2022 at 3:25 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > On Thu, Apr 21, 2022 at 02:28:45PM +0200, Arnd Bergmann wrote:
> > > We also know that larger slabs are all cacheline aligned, so simply
> > > comparing the transfer size is enough to rule out most, in this case
> > > any transfer larger than 96 bytes must come from the kmalloc-128
> > > or larger cache, so that works like before.
> >
> > There's also the case with 128-byte cache lines and kmalloc-192.
>
> Sure, but that's much less common, as the few machines with 128 byte
> cache lines tend to also have cache coherent devices IIRC, so we'd
> skip the bounce buffer entirely.
Do you know which machines still have 128-byte cache lines _and_
non-coherent DMA? If there isn't any that matters, I'd reduce
ARCH_DMA_MINALIGN to 64 now (while trying to get to even smaller kmalloc
caches).
> > > For transfers <=96 bytes, the possibilities are:
> > >
> > > 1.kmalloc-32 or smaller, always needs to bounce
> > > 2. kmalloc-96, but at least one byte in partial cache line,
> > > need to bounce
> > > 3. kmalloc-64, may skip the bounce.
> > > 4. kmalloc-128 or larger, or not a slab cache but a partial
> > > transfer, may skip the bounce.
> > >
> > > I would guess that the first case is the most common here,
> > > so unless bouncing one or two cache lines is extremely
> > > expensive, I don't expect it to be worth optimizing for the latter
> > > two cases.
> >
> > I think so. If someone complains of a performance regression, we can
> > look at optimising the bounce. I have a suspicion the cost of copying
> > two cache lines is small compared to swiotlb_find_slots() etc.
>
> That is possible, and we'd definitely have to watch out for
> performance regressions, I'm just skeptical that the cases that
> suffer from the extra bouncer buffering on 33..64 byte allocations
> benefit much from having a special case if the 1...32 and 65..96
> byte allocations are still slow.
>
> Another simpler way to do this might be to just not create the
> kmalloc-96 (or kmalloc-192) caches, and assuming that any
> transfer >=33 (or 65) bytes is safe.
I'll give the dma bounce idea a go next week, see how it looks.
--
Catalin
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next prev parent reply other threads:[~2022-04-21 14:45 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 [this message]
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
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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