a955318fe6
On RX an SKB is allocated and the received buffer is copied into it. But on some architectures, the memcpy() needs the source and destination buffers to have the same alignment to be efficient. This is not our case, because SKB data pointer is misaligned by two bytes to compensate the ethernet header. Align the RX buffer the same way as the SKB one, so the copy is faster. An iperf3 RX test gives a decent improvement on a RISC-V machine: before: [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 733 MBytes 615 Mbits/sec 88 sender [ 5] 0.00-10.01 sec 730 MBytes 612 Mbits/sec receiver after: [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 1.10 GBytes 942 Mbits/sec 0 sender [ 5] 0.00-10.00 sec 1.09 GBytes 940 Mbits/sec receiver And the memcpy() overhead during the RX drops dramatically. before: Overhead Shared O Symbol 43.35% [kernel] [k] memcpy 33.77% [kernel] [k] __asm_copy_to_user 3.64% [kernel] [k] sifive_l2_flush64_range after: Overhead Shared O Symbol 45.40% [kernel] [k] __asm_copy_to_user 28.09% [kernel] [k] memcpy 4.27% [kernel] [k] sifive_l2_flush64_range Signed-off-by: Matteo Croce <mcroce@microsoft.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.
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.