Usermodehelpers kernel threads are nohz-full unfriendly because they
force some explicit CPU-wide affinity that happen to disturb user code
that don't want to see noise on isolated CPUs.
So I spent many time on that, despite the one-liner end result.
The out-of-date comments didn't help much, especially it wasn't clear
why we need khelper at all, probably it was first introduced to bring
necessary asynchronous code but I couldn't justify that with the current
code.
I wrote patches to remove it but finally realized we still need it to
inherit a system wide (or nohz-full housekeeping) CPU affinity on
usermodehelper kernel threads because some usermodehelper callers may
have a reduced affinity (eg: per cpu workqueues). All I needed eventually
was to improve the comments to highlight that purpose. And remove a
nohz-full unfriendly wide affinity forcing.
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
nohz/kmod
HEAD: 9a0ad418b7739fbbe4add684551aa5582a58718b
Thanks,
Frederic
---
Frederic Weisbecker (3):
kmod: Bunch of internal functions renames
kmod: Add up-to-date explanations on the purpose of each asynchronous
levels
kmod: Remove unecessary explicit wide CPU affinity setting
kernel/kmod.c | 61 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 43 insertions(+), 18 deletions(-)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
