Messages in this thread Patch in this message | | | Subject | Re: [bpf] af7ec13833: will-it-scale.per_process_ops -2.5% regression | From | Rong Chen <> | Date | Fri, 3 Jul 2020 13:54:39 +0800 |
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On 6/29/20 11:10 PM, Yonghong Song wrote: > > > On 6/28/20 1:50 AM, kernel test robot wrote: >> Greeting, >> >> FYI, we noticed a -2.5% regression of will-it-scale.per_process_ops >> due to commit: >> >> >> commit: af7ec13833619e17f03aa73a785a2f871da6d66b ("bpf: Add >> bpf_skc_to_tcp6_sock() helper") >> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master > > One of previous emails claims that > commit: 492e639f0c222784e2e0f121966375f641c61b15 ("bpf: Add > bpf_seq_printf and bpf_seq_write helpers") > is reponsible for 2.5% improvement for will-it-scale.per_process_ops, > which I believe is false. > > This commit should not cause regression. > > Probably the variation of performance is caused by test environment > which you may want to investigate further to reduce false alarming. > Thanks!
Hi Yonghong,
It's a function align issue, the commit effects the align of functions which causes a little regression, we force to set -falign-functions=32 in KBUILD_CFLAGS and the regression is gone:
diff --git a/Makefile b/Makefile index 70def4907036c..9746afa4edc21 100644 --- a/Makefile +++ b/Makefile @@ -476,7 +476,7 @@ LINUXINCLUDE := \ $(USERINCLUDE)
KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE -KBUILD_CFLAGS := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \ +KBUILD_CFLAGS := -Wall -Wundef -falign-functions=32 -Werror=strict-prototypes -Wno-trigraphs \ -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \ -Werror=implicit-function-declaration -Werror=implicit-int \ -Wno-format-security \
Best Regards, Rong Chen
> >> >> in testcase: will-it-scale >> on test machine: 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ >> 2.30GHz with 192G memory >> with following parameters: >> >> nr_task: 16 >> mode: process >> test: mmap1 >> cpufreq_governor: performance >> ucode: 0x5002f01 >> >> test-description: Will It Scale takes a testcase and runs it from 1 >> through to n parallel copies to see if the testcase will scale. It >> builds both a process and threads based test in order to see any >> differences between the two. >> test-url: https://github.com/antonblanchard/will-it-scale >> >> >> >> If you fix the issue, kindly add following tag >> Reported-by: kernel test robot <rong.a.chen@intel.com> >> >> >> Details are as below: > [...]
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