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Date: Fri, 10 Dec 2010 06:59:58 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Andi Kleen <andi@...stfloor.org>, linux-kernel <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>, Tejun Heo <tj@...nel.org>, Rusty Russell <rusty@...tcorp.com.au>, Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com> Subject: Re: [PATCH v2 3/4] kthread: NUMA aware kthread_create_on_cpu() Le jeudi 09 décembre 2010 à 16:44 -0800, Andrew Morton a écrit : > The name "kthread_create_on_cpu" is pretty misleading. > > One would expect such a function to create a kthread which is bound to > that CPU. But what it in fact does is to create a kthread which is > bound to all CPUs and whose stack, task_struct and thread_info were > allocated from the node which contains `cpu'. > > Also, a saner interface would be one which takes the numa_node_id, not > the cpu number. > > > > > ... > > > > /** > > - * kthread_create - create a kthread. > > + * kthread_create_on_cpu - create a kthread. > > * @threadfn: the function to run until signal_pending(current). > > * @data: data ptr for @threadfn. > > + * @cpu: cpu number. > > * @namefmt: printf-style name for the thread. > > * > > * Description: This helper function creates and names a kernel > > * thread. The thread will be stopped: use wake_up_process() to start > > * it. See also kthread_run(). > > * > > + * If thread is going to be bound on a particular cpu, give its number > > + * in @cpu, to get NUMA affinity for kthread stack, or else give -1. > > This is a bit presumptuous. The caller might wish to later bind this > thread to some or all of the CPUs on the node, rather than to a single > CPU (eg, kswapd()). > > > So what to do? Maybe add a new kthread_create_node() which prepares a > kthread whose memory is bound to that node, then add a > kthread_create_cpu() convenience wrapper around that? > We probably can add the "bind to cpu" as a fifth patch, to avoid one kthread_bind(p, cpu); done by these callers. My reasoning not including this kthread_bind(p, cpu) in initial patch series that I was focusing on NUMA properties first, not on scheduling (this part already runs correctly as far as I know) Thanks for taking the patch series, I was about to resubmit it today :) -- 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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