On Fri, Sep 25, 2020 at 11:27:54AM +0200, Greg KH wrote: > On Thu, Sep 24, 2020 at 08:21:07PM +0200, Thomas Gleixner wrote: > > On Thu, Sep 24 2020 at 08:33, Greg KH wrote: > > > On Wed, Sep 23, 2020 at 05:08:32PM -0700, Prasad Sodagudi wrote: > > >> +config CONSOLE_FLUSH_ON_HOTPLUG > > >> + bool "Enable console flush configurable in hot plug code path"
> > CPU hotplug is not meant to be a high speed operation and if people > > think they need it to be fast then its pretty much guaranteed that they > > want it for the completely wrong reasons. > > Odds are, it's the big/little systems that are trying to use cpu hotplug > for this type of thing :( Just a bit of info: My MT6797X (10 core: 4×A53 + 4×A53 + 2×A72), flickers its cores this way: the right-hand piece is CPUs, one character per core: bars show utilization, "o" stands for offline; every line is 0.1 second interval. topline -i 0.1 mmcblk(⠀) (oooo▄▆oo▅o) mmcblk(⠀) (oooo▅▄oooo) mmcblk(⠀) (oooo▆▆oooo) mmcblk(⠀) (oooo▅ooo▆o) mmcblk(⠀) (oooo▆▆oo▄o) mmcblk(⠀) (oooo▆▇oooo) mmcblk(⠀) (oooo▇ooo▅o) mmcblk(⠀) (oooo▆ooo█o) mmcblk(⠀) (oooo▆ooo▄o) mmcblk(⠀) (oooo▅ooo▆o) mmcblk(⠀) (oooo▆ooo▅o) mmcblk(⠀) (oooo▄ooo▇o) mmcblk(⠀) (oooo▇▆oo▆o) mmcblk(⠀) (oooo▆ooo▅o) mmcblk(⠀) (oooo▅▆oooo) mmcblk(⠀) (oooo▆█oooo) mmcblk(⠀) (oooo▆▇oooo) mmcblk(⠀) (oooo▆▆oooo) mmcblk(⠀) (oooo▅▆oooo) mmcblk(⠀) (oooo▆▅oooo) mmcblk(⠀) (oooo▆ooo▆o) mmcblk(⠀) (oooo▆ooo▇o) mmcblk(⢀) (oooo▆▇oo▆o) mmcblk(⠀) (oooo▄ooo▆o) mmcblk(⠀) (oooo▆ooo█o) mmcblk(⠀) (oooo▄ooo▇o) mmcblk(⠀) (oooo▄▆oooo) mmcblk(⠀) (oooo▆▆oooo) So it's on the order of a few ons/offs per second. The offline CPUs are "present" and "offline"; not sure if this means hotplug or not (I'd expect dropping from "present" to "possible", but I don't know these parts). Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢠⠒⠀⣿⡁ in the beginning was the boot and root floppies and they were good. ⢿⡄⠘⠷⠚⠋⠀ -- <willmore> on #linux-sunxi ⠈⠳⣄⠀⠀⠀⠀