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.
Forked from
Linaro / linux / kernel / torvalds / linux
168730 commits behind the upstream repository.
Anton Protopopov
authored
The BPF hashmap uses the jhash() hash function. There is an optimized version
of this hash function which may be used if hash size is a multiple of 4. Apply
this optimization to the hashmap in a similar way as it is done in the bloom
filter map.
On practice the optimization is only noticeable for smaller key sizes, which,
however, is sufficient for many applications. An example is listed in the
following table of measurements (a hashmap of 65536 elements was used):
--------------------------------------------------------------------
| key_size | fullness | lookups /sec | lookups (opt) /sec | gain |
--------------------------------------------------------------------
| 4 | 25% | 42.990M | 46.000M | 7.0% |
| 4 | 50% | 37.910M | 39.094M | 3.1% |
| 4 | 75% | 34.486M | 36.124M | 4.7% |
| 4 | 100% | 31.760M | 32.719M | 3.0% |
--------------------------------------------------------------------
| 8 | 25% | 43.855M | 49.626M | 13.2% |
| 8 | 50% | 38.328M | 42.152M | 10.0% |
| 8 | 75% | 34.483M | 38.088M | 10.5% |
| 8 | 100% | 31.306M | 34.686M | 10.8% |
--------------------------------------------------------------------
| 12 | 25% | 38.398M | 43.770M | 14.0% |
| 12 | 50% | 33.336M | 37.712M | 13.1% |
| 12 | 75% | 29.917M | 34.440M | 15.1% |
| 12 | 100% | 27.322M | 30.480M | 11.6% |
--------------------------------------------------------------------
| 16 | 25% | 41.491M | 41.921M | 1.0% |
| 16 | 50% | 36.206M | 36.474M | 0.7% |
| 16 | 75% | 32.529M | 33.027M | 1.5% |
| 16 | 100% | 29.581M | 30.325M | 2.5% |
--------------------------------------------------------------------
| 20 | 25% | 34.240M | 36.787M | 7.4% |
| 20 | 50% | 30.328M | 32.663M | 7.7% |
| 20 | 75% | 27.536M | 29.354M | 6.6% |
| 20 | 100% | 24.847M | 26.505M | 6.7% |
--------------------------------------------------------------------
| 24 | 25% | 36.329M | 40.608M | 11.8% |
| 24 | 50% | 31.444M | 35.059M | 11.5% |
| 24 | 75% | 28.426M | 31.452M | 10.6% |
| 24 | 100% | 26.278M | 28.741M | 9.4% |
--------------------------------------------------------------------
| 28 | 25% | 31.540M | 31.944M | 1.3% |
| 28 | 50% | 27.739M | 28.063M | 1.2% |
| 28 | 75% | 24.993M | 25.814M | 3.3% |
| 28 | 100% | 23.513M | 23.500M | -0.1% |
--------------------------------------------------------------------
| 32 | 25% | 32.116M | 33.953M | 5.7% |
| 32 | 50% | 28.879M | 29.859M | 3.4% |
| 32 | 75% | 26.227M | 26.948M | 2.7% |
| 32 | 100% | 23.829M | 24.613M | 3.3% |
--------------------------------------------------------------------
| 64 | 25% | 22.535M | 22.554M | 0.1% |
| 64 | 50% | 20.471M | 20.675M | 1.0% |
| 64 | 75% | 19.077M | 19.146M | 0.4% |
| 64 | 100% | 17.710M | 18.131M | 2.4% |
--------------------------------------------------------------------
The following script was used to gather the results (SMT & frequency off):
cd tools/testing/selftests/bpf
for key_size in 4 8 12 16 20 24 28 32 64; do
for nr_entries in `seq 16384 16384 65536`; do
fullness=$(printf '%3s' $((nr_entries*100/65536)))
echo -n "key_size=$key_size: $fullness% full: "
sudo ./bench -d2 -a bpf-hashmap-lookup --key_size=$key_size --nr_entries=$nr_entries --max_entries=65536 --nr_loops=2000000 --map_flags=0x40 | grep cpu
done
echo
done
Signed-off-by: 
Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230401200602.3275-1-aspsk@isovalent.com
Signed-off-by: 
Alexei Starovoitov <ast@kernel.org>