Recompiling the kernel causes the CPU USE% to decrease

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In RHEL8.1BETA,when I recompiled the kernel with kernel-4.18.0-107.el8.src.rpm file,I found that the throughput value measured using Iperf has risen and the %use of the CPU has decreased.

Here are the steps I have to recompile the kernel.

1.# rpm -ivh kernel-4.18.0-107.el8.src.rpm
2.# cd /root/rpmbuild/SPEC
3.# rpmbuild -bp kernel.spec
4.# cd /root/rpmbuild/BUILD/kernel-4.18.0-107.el8/linux-4.18.0-107.el8.x86_64
5.# cp /boot/config-4.18.0-107.el8.x86_64 .config
6.# make -j56
7.# make
8.# make modules_install
9.# make install

I want to know why just recompiling the kernel will cause this situation.

Thanks

Responses

I suggest you run ps and see if you find defunct processes. ps -f should show you what produced them. If you have many of them, they would occupy as many CPUs, so slow down the whole build run. As far as I can tell, those defunct processes eventually disappear but this is really an annoying issue.

Currently I don't know how to prevent this from happening. This problem seems to be new in RHEL 8.

Have you encountered a similar situation?

I did not find any changes before and after recompiling the kernel with ps -f.

Thanks.

Have you encountered a similar situation?

I did not find any changes before and after recompiling the kernel with ps -f.

Thanks.