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Date: Thu, 12 Sep 2013 20:35:05 +0200 From: Frederic Weisbecker <fweisbec@...il.com> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Cc: Christoph Lameter <cl@...ux.com>, Andrew Morton <akpm@...ux-foundation.org>, Gilad Ben-Yossef <gilad@...yossef.com>, Thomas Gleixner <tglx@...utronix.de>, Mike Frysinger <vapier@...too.org>, linux-kernel@...r.kernel.org Subject: Re: [RFC] Restrict kernel spawning of threads to a specified set of cpus. On Thu, Sep 12, 2013 at 08:39:22AM -0700, Paul E. McKenney wrote: > On Thu, Sep 12, 2013 at 05:11:04PM +0200, Frederic Weisbecker wrote: > > On Thu, Sep 12, 2013 at 02:52:56PM +0000, Christoph Lameter wrote: > > > On Thu, 12 Sep 2013, Frederic Weisbecker wrote: > > > > > > > > > Ok but you can change the affinity of a kthread from userspace, as > > > > > > long as you define a cpu set that is among that kthread's cpus allowed. > > > > > > > > > > Ok but at that point kthread has already spawned a lot of kernel threads. > > > > > > > > > > The same is true for init and kmod. > > > > > > > > > > > > > Ok but then we just need to set the affinity of all these kthreads. > > > > A simple lookup on /proc/[0-9]+/ should do the trick. > > > > > > Yea but the kernel option makes it easy. No extras needed. Kernel brings > > > it up user space cleanly configured and ready to go. > > > > Ok but really that's just two lines of bash. I really wish we don't complicate > > core kernel code for that. > > OK, I will bite... How do you handle the case where you have collected > all the kthreads, one of the kthreads spawns another kthread, then you > set affinity on the collected kthreads, which does not include the newly > spawned one? Just offline the CPUs you want to isolate, affine your kthreads and re-online the CPUs. If you're lucky enough to have 1024 CPUs, a winter night should be enough ;-) -- 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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