Messages in this thread | | | Date | Thu, 9 Dec 2010 22:32:10 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v2 3/4] kthread: NUMA aware kthread_create_on_cpu() |
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On Fri, 10 Dec 2010 06:59:58 +0100 Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Le jeudi 09 d__cembre 2010 __ 16:44 -0800, Andrew Morton a __crit : > > > 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 :) >
but but but. The name "kthread_create_on_cpu" sucks. It's plain wrong.
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