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Message-ID: <47B26B21.3000108@qualcomm.com> Date: Tue, 12 Feb 2008 19:59:29 -0800 From: Max Krasnyansky <maxk@...lcomm.com> To: Peter Zijlstra <a.p.zijlstra@...llo.nl> CC: Andrew Morton <akpm@...ux-foundation.org>, torvalds@...ux-foundation.org, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Paul Jackson <pj@....com>, gregkh@...e.de, Rusty Russell <rusty@...tcorp.com.au>, Oleg Nesterov <oleg@...sign.ru>, Thomas Gleixner <tglx@...utronix.de>, Steven Rostedt <rostedt@...dmis.org> Subject: Re: [git pull for -mm] CPU isolation extensions (updated2) Peter Zijlstra wrote: > On Mon, 2008-02-11 at 20:10 -0800, Max Krasnyansky wrote: >> Andrew, looks like Linus decided not to pull this stuff. >> Can we please put it into -mm then. >> >> My tree is here >> git://git.kernel.org/pub/scm/linux/kernel/git/maxk/cpuisol-2.6.git >> Please use 'master' branch (or 'for-linus' they are identical). > > I'm wondering why you insist on offering a git tree that bypasses the > regular maintainers. Why not post the patches and walk the normal route? > > To me this feels rather aggressive, which makes me feel less inclined to > look at it. Peter, it may sound stupid but I'm honestly not sure what you mean. Please bear with me I do not mean to sounds arrogant. I'm looking for advice here. So here are some questions: - First, who would the regular maintainer be in this case ? I felt that cpu isolation can just sit in its own tree since it does not seem to belong to any existing stuff. So far people suggested -mm and -shed. I do not think it has much to do much with the -sched. -mm seems more general purpose, since Linus did not pull it directly I asked Andrew to take this stuff into -mm. He was already ok with the patches when I sent original pull request to Linus. - Is it not easier for a regular maintainer (whoever it turns out to be in this case) to pull from GIT rather than use patches ? In any case I did post patches along with pull request. So for example if Andrew prefers patches he could take those instead of the git. In fact if you look at my email I mentioned that if needed I can repost the patches. - And last but not least I want to be able to just tell people who want to use CPU isolation "Go get get this tree and use it". Git it the best for that. I can see how pull request to Linus may have been a bit aggressive. But then again I posted patches (_without_ pull request). Got feedback from You, Paul and couple of other guys. Addressed/explained issues/questions. Posted patches again (_without_ pull request). Got _zero_ replies even though folks who replied to the first patchset were replying to other things in the same timeframe. So I figured since I addressed everything you guys are happy, why not push it to Linus. So what did I do wrong ? Max >> ---- >> >> Diffstat: >> Documentation/ABI/testing/sysfs-devices-system-cpu | 41 +++++++ >> Documentation/cpu-isolation.txt | 113 +++++++++++++++++++++ >> arch/x86/Kconfig | 1 >> arch/x86/kernel/genapic_flat_64.c | 4 >> drivers/base/cpu.c | 48 ++++++++ >> include/linux/cpumask.h | 3 >> kernel/Kconfig.cpuisol | 42 +++++++ >> kernel/Makefile | 4 >> kernel/cpu.c | 54 ++++++++++ >> kernel/sched.c | 36 ------ >> kernel/stop_machine.c | 8 + >> kernel/workqueue.c | 30 ++++- >> 12 files changed, 337 insertions(+), 47 deletions(-) >> >> This addresses all Andrew's comments for the last submission. Details here: >> http://marc.info/?l=linux-kernel&m=120236394012766&w=2 >> >> There are no code changes since last time, besides minor fix for moving on-stack array >> to __initdata as suggested by Andrew. Other stuff is just documentation updates. >> >> List of commits >> cpuisol: Make cpu isolation configrable and export isolated map >> cpuisol: Do not route IRQs to the CPUs isolated at boot >> cpuisol: Do not schedule workqueues on the isolated CPUs >> cpuisol: Move on-stack array used for boot cmd parsing into __initdata >> cpuisol: Documentation updates >> cpuisol: Minor updates to the Kconfig options >> cpuisol: Do not halt isolated CPUs with Stop Machine >> >> I suggested by Ingo I'm CC'ing everyone who is even remotely connected/affected ;-) > > You forgot Oleg, he does a lot of the workqueue work. > > I'm worried by your approach to never start any workqueue on these cpus. > Like you said, it breaks Oprofile and others who depend on cpu local > workqueues being present. > > Under normal circumstances these workqueues will not do any work, > someone needs to provide work for them. That is, workqueues are passive. > > So I think your approach is the wrong way about. Instead of taking the > workqueue away, take away those that generate the work. > >> Ingo, Peter - Scheduler. >> There are _no_ changes in this area besides moving cpu_*_map maps from kerne/sched.c >> to kernel/cpu.c. > > Ingo (and Thomas) do the genirq bits > > The IRQ isolation in concept isn't wrong. But it seems to me that > arch/x86/kernel/genapic_flat_64.c isn't the best place to do this. > It just considers one architecture, if you do this, please make it work > across all. > >> Paul - Cpuset >> Again there are _no_ changes in this area. >> For reasons why cpuset is not the right mechanism for cpu isolation see this thread >> http://marc.info/?l=linux-kernel&m=120180692331461&w=2 >> >> Rusty - Stop machine. >> After doing a bunch of testing last three days I actually downgraded stop machine >> changes from [highly experimental] to simply [experimental]. Pleas see this thread >> for more info: http://marc.info/?l=linux-kernel&m=120243837206248&w=2 >> Short story is that I ran several insmod/rmmod workloads on live multi-core boxes >> with stop machine _completely_ disabled and did no see any issues. Rusty did not get >> a chance to reply yet, I hopping that we'll be able to make "stop machine" completely >> optional for some configurations. > > I too am thinking this is very wrong, stop machine is used by a lot of > things, including those that modify the kernel code. You really need to > replace all stop machine users with a more robust solution before you > can do this. > >> Gerg - ABI documentation. >> Nothing interesting here. I simply added >> Documentation/ABI/testing/sysfs-devices-system-cpu >> and documented some of the attributes exposed in there. >> Suggested by Andrew. > > Not having seen the latest patches; I'm still not fond of the isolation > interface. > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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