From: Christoph Hellwig <hch@lst.de>
To: Petr Tesarik <petrtesarik@huaweicloud.com>
Cc: Christoph Hellwig <hch@lst.de>, Jonathan Corbet <corbet@lwn.net>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>, Borislav Petkov <bp@suse.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Randy Dunlap <rdunlap@infradead.org>,
Damien Le Moal <damien.lemoal@opensource.wdc.com>,
Kim Phillips <kim.phillips@amd.com>,
"Steven Rostedt (Google)" <rostedt@goodmis.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:DMA MAPPING HELPERS" <iommu@lists.linux.dev>,
Roberto Sassu <roberto.sassu@huawei.com>,
petr@tesarici.cz, Alexander Graf <graf@amazon.com>
Subject: Re: [RFC v1 3/4] swiotlb: Allow dynamic allocation of bounce buffers
Date: Fri, 7 Apr 2023 07:57:04 +0200 [thread overview]
Message-ID: <20230407055704.GD6803@lst.de> (raw)
In-Reply-To: <8cf7c515-9ce6-a2ed-0643-972aa3eba2fb@huaweicloud.com>
On Tue, Mar 28, 2023 at 02:43:03PM +0200, Petr Tesarik wrote:
> Oh, wait! I can do at least something for devices which do not use
> swiotlb at all.
>
> If a device does not use bounce buffers, it cannot pass an address
> that belongs to the swiotlb. Consequently, the potentially
> expensive check can be skipped. This avoids the dynamic lookup
> penalty for devices which do not need the swiotlb.
>
> Note that the counter always remains zero if dma_io_tlb_mem is
> NULL, so the NULL check is not required.
Hmm, that's yet another atomic for each map/unmap, and bloats
struct device.
(Btw, in case anyone is interested, we really need to get started
on moving the dma fields out of struct device into a sub-struct
only allocated for DMA capable busses)
next prev parent reply other threads:[~2023-04-07 5:57 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 12:28 [RFC v1 0/4] Allow dynamic allocation of software IO TLB bounce buffers Petr Tesarik
2023-03-20 12:28 ` [RFC v1 1/4] dma-mapping: introduce the DMA_ATTR_MAY_SLEEP attribute Petr Tesarik
2023-03-28 3:57 ` Christoph Hellwig
2023-03-28 7:21 ` Petr Tesarik
2023-04-07 5:52 ` Christoph Hellwig
2023-03-31 13:06 ` Bagas Sanjaya
2023-03-20 12:28 ` [RFC v1 2/4] swiotlb: Move code around in preparation for dynamic bounce buffers Petr Tesarik
2023-03-20 12:28 ` [RFC v1 3/4] swiotlb: Allow dynamic allocation of " Petr Tesarik
2023-03-28 4:07 ` Christoph Hellwig
2023-03-28 7:54 ` Petr Tesarik
2023-03-28 12:43 ` Petr Tesarik
2023-04-07 5:57 ` Christoph Hellwig [this message]
2023-04-07 10:15 ` Petr Tesařík
2023-04-13 11:09 ` Petr Tesarik
2023-04-21 13:03 ` Petr Tesařík
2023-04-21 14:58 ` Robin Murphy
2023-04-21 15:09 ` Petr Tesařík
2023-04-24 6:03 ` Christoph Hellwig
2023-03-31 7:26 ` Juerg Haefliger
2023-03-31 9:00 ` Petr Tesařík
2023-04-06 11:44 ` Juerg Haefliger
2023-05-11 10:36 ` Petr Tesařík
2023-04-07 5:55 ` Christoph Hellwig
2023-04-07 10:46 ` Petr Tesařík
2023-04-11 3:51 ` Christoph Hellwig
2023-03-20 12:28 ` [RFC v1 4/4] swiotlb: Add an option to allow dynamic " Petr Tesarik
2023-03-27 11:06 ` [RFC v1 0/4] Allow dynamic allocation of software IO TLB " Petr Tesarik
2023-04-07 6:00 ` Christoph Hellwig
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