From: Logan Gunthorpe <logang@deltatee.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
"Stephen Bates" <sbates@raithlin.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Christian König" <christian.koenig@amd.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Don Dutile" <ddutile@redhat.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Minturn Dave B" <dave.b.minturn@intel.com>,
"Jason Ekstrand" <jason@jlekstrand.net>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Xiong Jianxin" <jianxin.xiong@intel.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Ira Weiny" <ira.weiny@intel.com>,
"Robin Murphy" <robin.murphy@arm.com>,
"Martin Oliveira" <martin.oliveira@eideticom.com>,
"Chaitanya Kulkarni" <ckulkarnilinux@gmail.com>,
"Ralph Campbell" <rcampbell@nvidia.com>
Subject: Re: [PATCH v7 16/21] block: add check when merging zone device pages
Date: Thu, 30 Jun 2022 15:50:10 -0600 [thread overview]
Message-ID: <39bf0071-0acf-12fd-3d3e-06dfd87bb409@deltatee.com> (raw)
In-Reply-To: <7da06e08-7dd1-f37c-4382-bc59a1b1e819@deltatee.com>
On 2022-06-29 10:06, Logan Gunthorpe wrote:
>
>
>
> On 2022-06-29 00:46, Christoph Hellwig wrote:
>> On Wed, Jun 15, 2022 at 10:12:28AM -0600, Logan Gunthorpe wrote:
>>> Consecutive zone device pages should not be merged into the same sgl
>>> or bvec segment with other types of pages or if they belong to different
>>> pgmaps. Otherwise getting the pgmap of a given segment is not possible
>>> without scanning the entire segment. This helper returns true either if
>>> both pages are not zone device pages or both pages are zone device
>>> pages with the same pgmap.
>>>
>>> Add a helper to determine if zone device pages are mergeable and use
>>> this helper in page_is_mergeable().
>>
>> Any reason not to simply set REQ_NOMERGE for these requests? We
>> can't merge for passthrough requests anyway, and genrally don't merge
>> for direct I/O either, so adding all this overhead seems a bit pointless.
>
> Hmm, I suppose we could also ensure that REQ_NOMERGE is set in a bio
> before setting FOLL_PCI_P2PDMA in bio_map_user_iov() and
> __bio_iov_iter_get_pages(). Assuming it's always set for any direct I/O.
>
Oh, it turns out this code has nothing to do with REQ_NOMERGE. It's used
indirectly in bio_map_user_iov() and __bio_iov_iter_get_pages() when
adding pages to the bio via page_is_mergeable(). So it's not about
requests being merged it's about pages being merged.
So I'm not sure how we can avoid this, but it only happens when two
adjacent pages are added to the same bio in a row, so I don't think it's
that common, but the check can probably be moved down so it happens
after the same_page check to make it a little less common.
Logan
Logan
WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-pci@vger.kernel.org,
"Dave Hansen" <dave.hansen@linux.intel.com>,
linux-nvme@lists.infradead.org,
"Stephen Bates" <sbates@raithlin.com>,
linux-mm@kvack.org, "Jason Ekstrand" <jason@jlekstrand.net>,
"Ira Weiny" <ira.weiny@intel.com>,
"Minturn Dave B" <dave.b.minturn@intel.com>,
"Martin Oliveira" <martin.oliveira@eideticom.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Chaitanya Kulkarni" <ckulkarnilinux@gmail.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"John Hubbard" <jhubbard@nvidia.com>,
linux-block@vger.kernel.org,
"Dan Williams" <dan.j.williams@intel.com>,
"Xiong Jianxin" <jianxin.xiong@intel.com>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
"Robin Murphy" <robin.murphy@arm.com>,
"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v7 16/21] block: add check when merging zone device pages
Date: Thu, 30 Jun 2022 15:50:10 -0600 [thread overview]
Message-ID: <39bf0071-0acf-12fd-3d3e-06dfd87bb409@deltatee.com> (raw)
In-Reply-To: <7da06e08-7dd1-f37c-4382-bc59a1b1e819@deltatee.com>
On 2022-06-29 10:06, Logan Gunthorpe wrote:
>
>
>
> On 2022-06-29 00:46, Christoph Hellwig wrote:
>> On Wed, Jun 15, 2022 at 10:12:28AM -0600, Logan Gunthorpe wrote:
>>> Consecutive zone device pages should not be merged into the same sgl
>>> or bvec segment with other types of pages or if they belong to different
>>> pgmaps. Otherwise getting the pgmap of a given segment is not possible
>>> without scanning the entire segment. This helper returns true either if
>>> both pages are not zone device pages or both pages are zone device
>>> pages with the same pgmap.
>>>
>>> Add a helper to determine if zone device pages are mergeable and use
>>> this helper in page_is_mergeable().
>>
>> Any reason not to simply set REQ_NOMERGE for these requests? We
>> can't merge for passthrough requests anyway, and genrally don't merge
>> for direct I/O either, so adding all this overhead seems a bit pointless.
>
> Hmm, I suppose we could also ensure that REQ_NOMERGE is set in a bio
> before setting FOLL_PCI_P2PDMA in bio_map_user_iov() and
> __bio_iov_iter_get_pages(). Assuming it's always set for any direct I/O.
>
Oh, it turns out this code has nothing to do with REQ_NOMERGE. It's used
indirectly in bio_map_user_iov() and __bio_iov_iter_get_pages() when
adding pages to the bio via page_is_mergeable(). So it's not about
requests being merged it's about pages being merged.
So I'm not sure how we can avoid this, but it only happens when two
adjacent pages are added to the same bio in a row, so I don't think it's
that common, but the check can probably be moved down so it happens
after the same_page check to make it a little less common.
Logan
Logan
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next prev parent reply other threads:[~2022-06-30 21:50 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-15 16:12 [PATCH v7 00/21] Userspace P2PDMA with O_DIRECT NVMe devices Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 01/21] lib/scatterlist: add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:33 ` Christoph Hellwig
2022-06-29 6:33 ` Christoph Hellwig
2022-06-29 9:05 ` Robin Murphy
2022-06-29 9:05 ` Robin Murphy
2022-06-29 15:39 ` Logan Gunthorpe
2022-06-29 15:39 ` Logan Gunthorpe
2022-06-29 18:02 ` Robin Murphy
2022-06-29 18:02 ` Robin Murphy
2022-06-29 18:24 ` Logan Gunthorpe
2022-06-29 18:24 ` Logan Gunthorpe
2022-07-04 15:08 ` Robin Murphy
2022-07-04 15:08 ` Robin Murphy
2022-06-15 16:12 ` [PATCH v7 02/21] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:33 ` Christoph Hellwig
2022-06-29 6:33 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 03/21] PCI/P2PDMA: Expose pci_p2pdma_map_type() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:39 ` Christoph Hellwig
2022-06-29 6:39 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 04/21] PCI/P2PDMA: Introduce helpers for dma_map_sg implementations Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:39 ` Christoph Hellwig
2022-06-29 6:39 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 05/21] dma-mapping: allow EREMOTEIO return code for P2PDMA transfers Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:40 ` Christoph Hellwig
2022-06-29 6:40 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 06/21] dma-direct: support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:40 ` Christoph Hellwig
2022-06-29 6:40 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 07/21] dma-mapping: add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:41 ` Christoph Hellwig
2022-06-29 6:41 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 08/21] iommu/dma: support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 12:07 ` Robin Murphy
2022-06-29 12:07 ` Robin Murphy
2022-06-29 15:57 ` Logan Gunthorpe
2022-06-29 15:57 ` Logan Gunthorpe
2022-06-29 19:15 ` Robin Murphy
2022-06-29 19:15 ` Robin Murphy
2022-06-29 22:41 ` Logan Gunthorpe
2022-06-29 22:41 ` Logan Gunthorpe
2022-06-30 14:56 ` Robin Murphy
2022-06-30 14:56 ` Robin Murphy
2022-06-30 21:21 ` Logan Gunthorpe
2022-06-30 21:21 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 09/21] nvme-pci: check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:41 ` Christoph Hellwig
2022-06-29 6:41 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 10/21] nvme-pci: convert to using dma_map_sgtable() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:42 ` Christoph Hellwig
2022-06-29 6:42 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 11/21] RDMA/core: introduce ib_dma_pci_p2p_dma_supported() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:42 ` Christoph Hellwig
2022-06-29 6:42 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 12/21] RDMA/rw: drop pci_p2pdma_[un]map_sg() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:42 ` Christoph Hellwig
2022-06-29 6:42 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 13/21] PCI/P2PDMA: Remove pci_p2pdma_[un]map_sg() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:43 ` Christoph Hellwig
2022-06-29 6:43 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 14/21] mm: introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:45 ` Christoph Hellwig
2022-06-29 6:45 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 15/21] iov_iter: introduce iov_iter_get_pages_[alloc_]flags() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:45 ` Christoph Hellwig
2022-06-29 6:45 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 16/21] block: add check when merging zone device pages Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:46 ` Christoph Hellwig
2022-06-29 6:46 ` Christoph Hellwig
2022-06-29 16:06 ` Logan Gunthorpe
2022-06-29 16:06 ` Logan Gunthorpe
2022-06-30 21:50 ` Logan Gunthorpe [this message]
2022-06-30 21:50 ` Logan Gunthorpe
2022-07-04 6:07 ` Christoph Hellwig
2022-07-04 6:07 ` Christoph Hellwig
2022-06-15 16:12 ` [PATCH v7 17/21] lib/scatterlist: " Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 18/21] block: set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 19/21] block: set FOLL_PCI_P2PDMA in bio_map_user_iov() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:48 ` Christoph Hellwig
2022-06-29 6:48 ` Christoph Hellwig
2022-06-29 16:00 ` Logan Gunthorpe
2022-06-29 16:00 ` Logan Gunthorpe
2022-06-29 17:59 ` Jason Gunthorpe
2022-06-29 17:59 ` Jason Gunthorpe
2022-07-05 7:51 ` Christoph Hellwig
2022-07-05 7:51 ` Christoph Hellwig
2022-07-05 13:51 ` Jason Gunthorpe
2022-07-05 13:51 ` Jason Gunthorpe
2022-07-05 16:12 ` Christoph Hellwig
2022-07-05 16:12 ` Christoph Hellwig
2022-07-05 16:29 ` Jason Gunthorpe
2022-07-05 16:29 ` Jason Gunthorpe
2022-07-05 16:40 ` Christoph Hellwig
2022-07-05 16:40 ` Christoph Hellwig
2022-07-05 16:41 ` Logan Gunthorpe
2022-07-05 16:41 ` Logan Gunthorpe
2022-07-05 16:43 ` Christoph Hellwig
2022-07-05 16:43 ` Christoph Hellwig
2022-07-05 16:44 ` Logan Gunthorpe
2022-07-05 16:44 ` Logan Gunthorpe
2022-07-05 16:50 ` Christoph Hellwig
2022-07-05 16:50 ` Christoph Hellwig
2022-07-05 17:21 ` Greg Kroah-Hartman
2022-07-05 17:21 ` Greg Kroah-Hartman
2022-07-05 17:32 ` Logan Gunthorpe
2022-07-05 17:32 ` Logan Gunthorpe
2022-07-05 17:42 ` Greg Kroah-Hartman
2022-07-05 17:42 ` Greg Kroah-Hartman
2022-07-05 18:16 ` Logan Gunthorpe
2022-07-05 18:16 ` Logan Gunthorpe
2022-07-06 6:51 ` Christoph Hellwig
2022-07-06 6:51 ` Christoph Hellwig
2022-07-06 7:04 ` Greg Kroah-Hartman
2022-07-06 7:04 ` Greg Kroah-Hartman
2022-07-06 21:30 ` Logan Gunthorpe
2022-06-15 16:12 ` [PATCH v7 21/21] nvme-pci: allow mmaping the CMB in userspace Logan Gunthorpe
2022-06-15 16:12 ` Logan Gunthorpe
2022-06-29 6:49 ` [PATCH v7 00/21] Userspace P2PDMA with O_DIRECT NVMe devices Christoph Hellwig
2022-06-29 6:49 ` Christoph Hellwig
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