From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Joao Martins <joao.m.martins@oracle.com>,
John Hubbard <jhubbard@nvidia.com>,
Logan Gunthorpe <logang@deltatee.com>,
Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org, netdev@vger.kernel.org,
linux-mm@kvack.org, linux-rdma@vger.kernel.org,
dri-devel@lists.freedesktop.org, nvdimm@lists.linux.dev
Subject: Re: Phyr Starter
Date: Thu, 20 Jan 2022 15:03:40 +0100 [thread overview]
Message-ID: <20220120140340.GC11223@lst.de> (raw)
In-Reply-To: <Yd8fz4bY/aMMk24h@casper.infradead.org>
On Wed, Jan 12, 2022 at 06:37:03PM +0000, Matthew Wilcox wrote:
> But let's go further than that (which only brings us to 32 bytes per
> range). For the systems you care about which use an identity mapping,
> and have sizeof(dma_addr_t) == sizeof(phys_addr_t), we can simply
> point the dma_range pointer to the same memory as the phyr. We just
> have to not free it too early. That gets us down to 16 bytes per range,
> a saving of 33%.
Even without an IOMMU the dma_addr_t can have offsets vs the actual
physical address. Not on x86 except for a weirdo SOC, but just about
everywhere else.
next prev parent reply other threads:[~2022-01-20 14:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-10 19:34 Phyr Starter Matthew Wilcox
2022-01-11 0:41 ` Jason Gunthorpe
2022-01-11 4:32 ` Matthew Wilcox
2022-01-11 15:01 ` Jason Gunthorpe
2022-01-11 18:33 ` Matthew Wilcox
2022-01-11 20:21 ` Jason Gunthorpe
2022-01-11 21:25 ` Matthew Wilcox
2022-01-11 22:09 ` Logan Gunthorpe
2022-01-11 22:57 ` Jason Gunthorpe
2022-01-11 23:02 ` Logan Gunthorpe
2022-01-11 22:53 ` Jason Gunthorpe
2022-01-11 22:57 ` Logan Gunthorpe
2022-01-11 23:02 ` Jason Gunthorpe
2022-01-11 23:08 ` Logan Gunthorpe
2022-01-12 18:37 ` Matthew Wilcox
2022-01-12 19:08 ` Jason Gunthorpe
2022-01-20 14:03 ` Christoph Hellwig [this message]
2022-01-20 17:17 ` Jason Gunthorpe
2022-01-20 14:00 ` Christoph Hellwig
2022-01-11 9:05 ` Daniel Vetter
2022-01-11 20:26 ` Jason Gunthorpe
2022-01-20 14:09 ` Christoph Hellwig
2022-01-20 13:56 ` Christoph Hellwig
2022-01-20 15:27 ` Keith Busch
2022-01-20 15:28 ` Christoph Hellwig
2022-01-20 17:54 ` Robin Murphy
2022-01-11 8:17 ` John Hubbard
2022-01-11 14:01 ` Matthew Wilcox
2022-01-11 15:02 ` Jason Gunthorpe
2022-01-11 17:31 ` Logan Gunthorpe
2022-01-20 14:12 ` Christoph Hellwig
2022-01-20 21:35 ` John Hubbard
2022-01-11 11:40 ` Thomas Zimmermann
2022-01-11 13:56 ` Matthew Wilcox
2022-01-11 14:10 ` Thomas Zimmermann
2022-01-20 13:39 ` Christoph Hellwig
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