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Date: Fri, 8 Nov 2013 11:18:01 +0100 From: Jan Kara <jack@...e.cz> To: Steven Rostedt <rostedt@...dmis.org> Cc: Jan Kara <jack@...e.cz>, Frederic Weisbecker <fweisbec@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Michal Hocko <mhocko@...e.cz> Subject: Re: [PATCH 2/4] irq_work: Provide a irq work that can be processed on any cpu On Thu 07-11-13 18:31:42, Steven Rostedt wrote: > On Fri, 8 Nov 2013 00:01:11 +0100 > Jan Kara <jack@...e.cz> wrote: > > > On Thu 07-11-13 23:54:10, Frederic Weisbecker wrote: > > > > So if the current CPU can handle it, what is the problem? > > I hope this gets cleared out in my other email. But to make sure: If > > other CPUs are idle (i.e. not appending to the printk buffer), we can well > > handle the printing on the current CPU (with some breaks to allow > > interrupts to be served etc.). If other CPUs are also appending to printk > > buffer, that's where we really want to push the work to other CPUs. > > I guess the question is, how does it migrate? I guess that's not so > clear. Or do you just hope that the timer tick on another CPU will come > in first and finish the job for you? As the list is global and all CPUs > get to see it. There are two possibilities how the migration can happen: 1) a tick happens first on some other cpu and thus it will pick up the work 2) a printk happens first on some other cpu and thus it will pick printing in its console_unlock() call. I agree in both cases we depend on statistics, there's no real guarantee the migration happens. But in my testing this seems to be enough. Honza -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- 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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