On Thu, Nov 04, 2021 at 11:14:55AM -0700, Yi Fan wrote: > Resend the email using plain text. > > 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=v4.14.253&id=27d185697322f9547bfd381c71252ce0bc1c0ee4 > > 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=v5.14.15&id=3cffa06aeef7ece30f6b5ac0ea51f264e8fea4d0) > 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=v5.14.15&id=a91bd6223ecd46addc71ee6fcd432206d39365d2) > > 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
