Re: [PATCH v2 00/23] Cache aware scheduling

[Chen, Yu C]

On 12/19/2025 11:19 AM, Aaron Lu wrote:
> On Wed, Dec 03, 2025 at 03:07:19PM -0800, Tim Chen wrote:
> ... ...
> > Test results:
> >
> > The patch series was applied and tested on v6.18-rc7.
> > See: https://github.com/timcchen1298/linux/commits/cache_aware_v2
> >
> > The first test platform is a 2 socket Intel Sapphire Rapids with 30
> > cores per socket. The DRAM interleaving is enabled in the BIOS so it
> > essential has one NUMA node with two last level caches. There are 60
> > CPUs associated with each last level cache.
> >
> > The second test platform is a AMD Genoa. There are 4 Nodes and 32 CPUs
> > per node. Each node has 2 CCXs and each CCX has 16 CPUs.
> >
> > hackbench/schbench/netperf/stream/stress-ng/chacha20 were launched on
> > these two platforms.
> >
> > [TL;DR]
> > Sappire Rapids:
> > hackbench shows significant improvement when the number of
> > different active threads is below the capacity of a LLC.
> > schbench shows overall wakeup latency improvement.
> > ChaCha20-xiangshan shows good throughput improvement.
> >
> > Genoa:
> > ChaCha20-xiangshan shows huge throughput improvement.
> > No obvious difference is observed in hackbench/schbench
>
> I think for small task number hackbench run, there should be some
> improvement.
>
> I tried thread/pipe/2fds/1group, i.e. 4 tasks on Genoa:
> ./hackbench -T -f 2 -g 1 -p -l 2000000
> And I noticed performance improved a lot:
> (Result in seconds, less is better)
>
>         llc_off       llc_on          diff
> time   4.755±1.6%    2.684±6.25%    +43.6%
>
> llc_off means /sys/kernel/debug/sched/llc_enabled set to 0 while
> llc_on means /sys/kernel/debug/sched/llc_enabled set to 1, other
> tunnables are left unchanged.
> Turbo is disabled and cpufreq set to performance.
>
> I also tried redis and noticed when I set io-threads to 4 in redis.conf,
> there is also some improvement on AMD Genoa:
>
>                   llc_off        manual      diff     llc_on      diff
> throughput      1536727±0%     1737619±0%  +13.1%   1737720±0%  +13.1%
>
> Client cmdline:
> numactl -N 1 redis-benchmark --threads 4 -t set -r 100000 -P 16 -n 10000000
> server cmdline: numactl -N 0 redis-server ./redis.conf
> I also tried to manually bind all tasks of redis server to a single LLC
> to see if this workload benefits from aggregation and that's what manual
> means: taskset -c 8-15,200-207 redis-server ./redis.conf
>
> According to the result, I think this 'cache aware scheduling' works
> as expected in that its performance is the same as manual binding; and
> they all beat llc_off.

Thanks Aaron for the test!

thanks,
Chenyu