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Date: Thu, 10 Apr 2014 14:30:03 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Steven Rostedt <rostedt@...dmis.org> Cc: Peter Zijlstra <peterz@...radead.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Clark Williams <williams@...hat.com>, LKML <linux-kernel@...r.kernel.org>, linux-rt-users <linux-rt-users@...r.kernel.org>, Mike Galbraith <umgwanakikbuti@...il.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Thomas Gleixner <tglx@...utronix.de>, Frederic Weisbecker <fweisbec@...il.com>, Ingo Molnar <mingo@...nel.org> Subject: Re: [RFC PATCH RT] rwsem: The return of multi-reader PI rwsems On Thu, Apr 10, 2014 at 03:17:41PM -0400, Steven Rostedt wrote: > On Thu, 10 Apr 2014 17:36:17 +0200 > Peter Zijlstra <peterz@...radead.org> wrote: > > > > It defaults to the total number of CPUs in the system, given the default > > setup (all CPUs in a single balance domain), this should result in all > > CPUs working concurrently on the boosted read sides. > > Unfortunately, it currently defaults to the number of possible CPUs in > the system. I should probably move the default assignment to after SMP > is setup. Currently it happens in early boot before all the CPUs are > running. On boot up, the limit is set to NR_CPUS which should be much > higher than what the system has, but shouldn't matter during boot. But > after all the CPUs are up and running, it can lower it to online CPUs. Another approach is to use nr_cpu_ids, which is the maximum number of CPUs that the particular booting system could ever have. I use this in RCU to resize the data structures down from their NR_CPUS compile-time hugeness. Thanx, Paul > I think I'll go and make v3 of this patch. > > -- Steve > -- 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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