On 04/10/2015 05:11 PM, Andrew Morton wrote:
On Fri, 10 Apr 2015 16:48:18 -0400 Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote:
This change allows some cores to be excluded from running the
smp_hotplug_thread tasks. The motivating example for this is
the watchdog threads, which by default we don't want to run
on any enabled nohz_full cores.
Why not?
Thanks for the feedback. It's easy to assume everyone knows
everything about what's being done in the kernel :-)
I'll add some more descriptive language around what the point
of nohz_full is, and why the watchdog interferes with it, in v8.
I can guess, but I'd rather not guess. Please fully explain the
end-user value of this change. Providing a benefit to users is the
whole point of the patchset, but the above assertion is the only
description we have.
This info should be in Documentation/lockup-watchdogs.txt and/or
Documentation/sysctl/kernel.txt as well as the changelogs, so users
have an answer to "why the heck should I enable this".
Please also describe the downside of the change. I assume this is
"lockups will go undetected on some CPUs"? Let's expand on this so we
can understand where the best tradeoff point lies.
If people are experiencing <whatever this problem is> then they can
disable the watchdog altogether. What value is there in this partial
disabling? Why is it worth doing this?
--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
