On Thu, Nov 04, 2021 at 11:14:55AM -0700, Yi Fan wrote:
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I found some kernel performance regression issues that might be related w/ 4.14.y LTS commit.
4.14.y commit: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v...
The issue is observed when "console=" is used as a kernel parameter to disable the kernel console.
What exact "performance issue" are you seeing?
And what kernel version are you seeing it on?
I browsed android common kernel logs and the upstream stable kernel tree, found some related changes.
printk: handle blank console arguments passed in. (link: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v...) Revert "init/console: Use ttynull as a fallback when there is no console" (link: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v...)
It looks like upstream also noticed the regression introduced by the commit, and the workaround is to use "ttynull" to handle "console=" case. But the "ttynull" was reverted due to some other reasons mentioned in the commit message.
Any insight or recommendation will be appreciated.
What problem exactly are you now seeing? And does it also happen on 5.15?
thanks,
greg k-h