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c055e3eae0
Currently, we use the jiffies counter as a time source, by staring at it until a HZ period elapses, and then staring at it again and perform as many XOR operations as we can at the same time until another HZ period elapses, so that we can calculate the throughput. This takes longer than necessary, and depends on HZ, which is undesirable, since HZ is system dependent. Let's use the ktime interface instead, and use it to time a fixed number of XOR operations, which can be done much faster, and makes the time spent depend on the performance level of the system itself, which is much more reasonable. To ensure that we have the resolution we need even on systems with 32 kHz time sources, while not spending too much time in the benchmark on a slow CPU, let's switch to 3 attempts of 800 repetitions each: that way, we will only misidentify algorithms that perform within 10% of each other as the fastest if they are faster than 10 GB/s to begin with, which is not expected to occur on systems with such coarse clocks. On ThunderX2, I get the following results: Before: [72625.956765] xor: measuring software checksum speed [72625.993104] 8regs : 10169.000 MB/sec [72626.033099] 32regs : 12050.000 MB/sec [72626.073095] arm64_neon: 11100.000 MB/sec [72626.073097] xor: using function: 32regs (12050.000 MB/sec) After: [72599.650216] xor: measuring software checksum speed [72599.651188] 8regs : 10491 MB/sec [72599.652006] 32regs : 12345 MB/sec [72599.652871] arm64_neon : 11402 MB/sec [72599.652873] xor: using function: 32regs (12345 MB/sec) Link: https://lore.kernel.org/linux-crypto/20200923182230.22715-3-ardb@kernel.org/ Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> |
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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.