Re: [LKP] Re: 2463a604a8: netperf.Throughput_tps 12.8% improvement

From: Xing Zhengjun
Date: Tue May 25 2021 - 21:50:20 EST

On 5/26/2021 12:44 AM, Bart Van Assche wrote:
On 5/24/21 11:44 PM, kernel test robot wrote:
FYI, we noticed a 12.8% improvement of netperf.Throughput_tps due to commit:

commit: 2463a604a86728777ce4284214a52de46a808c9e ("[PATCH v3 2/3] Introduce enums for the SAM, message, host and driver status codes")
base: for-next

in testcase: netperf
on test machine: 192 threads 4 sockets Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory
with following parameters:

ip: ipv4
runtime: 300s
nr_threads: 16
cluster: cs-localhost
test: TCP_CRR
cpufreq_governor: performance
ucode: 0x5003006

test-description: Netperf is a benchmark that can be use to measure various aspect of networking performance.
The above email reports a performance improvement for the networking
subsystem while my patch only affects the SCSI subsystem and should not
have any performance impact. I'm confused by the above feedback ...

I suspect it related with cache alignment, 2463a604a8 changes "u8" (size:1) to "enum xxx_status" (size: 4),  the cache alignment is better than before , so cause the improvement.

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Zhengjun Xing