Following patch series extends CPU isolation support. Yes, most people want to
virtuallize
CPUs these days and I want to isolate them :).
The primary idea here is to be able to use some CPU cores as dedicated engines
for running
user-space code with minimal kernel overhead/intervention, think of it as an
SPE in the
Cell processor.
We've had scheduler support for CPU isolation ever since O(1) scheduler went
it.
I'd like to extend it further to avoid kernel activity on those CPUs as much as
possible.
In fact that the primary distinction that I'm making between say "CPU sets" and
"CPU isolation". "CPU sets" let you manage user-space load while "CPU
isolation" provides
a way to isolate a CPU as much as possible (including kernel activities).
I'm personally using this for hard realtime purposes. With CPU isolation it's
very easy to
achieve single digit usec worst case and around 200 nsec average response times
on off-the-shelf
multi- processor/core systems under exteme system load. I'm working with legal
folks on releasing
hard RT user-space framework for that.
I can also see other application like simulators and stuff that can benefit
from this.
I've been maintaining this stuff since around 2.6.18 and it's been running in
production
environment for a couple of years now. It's been tested on all kinds of
machines, from NUMA
boxes like HP xw9300/9400 to tiny uTCA boards like Mercury AXA110.
The messiest part used to be SLAB garbage collector changes. With the new SLUB
all that mess
goes away (ie no changes necessary). Also CFS seems to handle CPU hotplug much
better than O(1)
did (ie domains are recomputed dynamically) so that isolation can be done at
any time (via sysfs).
So this seems like a good time to merge.
Anyway. The patchset consist of 5 patches. First three are very simple and
non-controversial.
They simply make "CPU isolation" a configurable feature, export
cpu_isolated_map and provide
some helper functions to access it (just like cpu_online() and friends).
Last two patches add support for isolating CPUs from running workqueus and stop
machine.
More details in the individual patch descriptions.
Ideally I'd like all of this to go in during this merge window. If people think
it's acceptable
Linus or Andrew (or whoever is more appropriate Ingo maybe) can pull this patch
set from
git://git.kernel.org/pub/scm/linux/kernel/git/maxk/cpuisol-2.6.git
That tree is rebased against latest (as of yesterday) Linus' tree.
Thanx
Max
arch/x86/Kconfig | 1
arch/x86/kernel/genapic_flat_64.c | 5 ++--
drivers/base/cpu.c | 47 ++++++++++++++++++++++++++++++++++++++
include/linux/cpumask.h | 3 ++
kernel/Kconfig.cpuisol | 25 +++++++++++++++++++-
kernel/sched.c | 13 ++++++----
kernel/stop_machine.c | 3 --
kernel/workqueue.c | 31 ++++++++++++++++++-------
8 files changed, 110 insertions(+), 18 deletions(-)
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