069d11465a
Enhance the memory scheme of the legacy RQ, such that only order-0 pages are used. Whenever possible, prefer using a linear SKB, and build it wrapping the WQE buffer. Otherwise (for example, jumbo frames on x86), use non-linear SKB, with as many frags as needed. In this case, multiple WQE scatter entries are used, up to a maximum of 4 frags and 10KB of MTU. This implied to remove support of HW LRO in legacy RQ, as it would require large number of page allocations and scatter entries per WQE on archs with PAGE_SIZE = 4KB, yielding bad performance. In earlier patches, we guaranteed that all completions are in-order, and that we use a cyclic WQ. This creates an oppurtunity for a performance optimization: The mapping between a "struct mlx5e_dma_info", and the WQEs (struct mlx5e_wqe_frag_info) pointing to it, is constant across different cycles of a WQ. This allows initializing the mapping in the time of RQ creation, and not handle it in datapath. A struct mlx5e_dma_info that is shared between different WQEs is allocated by the first WQE, and freed by the last one. This implies an important requirement: WQEs that share the same struct mlx5e_dma_info must be posted within the same NAPI. Otherwise, upon completion, struct mlx5e_wqe_frag_info would mistakenly point to the new struct mlx5e_dma_info, not the one that was posted (and the HW wrote to). This bulking requirement is actually good also for performance reasons, hence we extend the bulk beyong the minimal requirement above. With this memory scheme, the RQs memory footprint is reduce by a factor of 2 on x86, and by a factor of 32 on PowerPC. Same factors apply for the number of pages in a GRO session. Performance tests: ConnectX-4, single core, single RX ring, default MTU. x86: CPU: Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz Packet rate (early drop in TC): no degradation TCP streams: ~5% improvement PowerPC: CPU: POWER8 (raw), altivec supported Packet rate (early drop in TC): 20% gain TCP streams: 25% gain Signed-off-by: Tariq Toukan <tariqt@mellanox.com> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com> |
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| arch | ||
| block | ||
| certs | ||
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| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
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| COPYING | ||
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| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.