Messages in this thread | | | Date | Mon, 12 Apr 2010 17:24:30 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by using percpu counter |
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Oleg Nesterov wrote: > On 04/07, Oleg Nesterov wrote: >> On 04/07, Lai Jiangshan wrote: >>> Old get_online_cpus() is read-preference, I think the goal of this ability >>> is allow get_online_cpus()/put_online_cpus() to be called nested. >> Sure, I understand why you added task_struct->get_online_cpus_nest. >> >>> and use per-task counter for allowing get_online_cpus()/put_online_cpus() >>> to be called nested, I think this deal is absolutely worth. >> As I said, I am not going to argue. I can't justify this tradeoff. > > But, I must admit, I'd like to avoid adding the new member to task_struct. > > What do you think about the code below? > > I didn't even try to compile it, just to explain what I mean. > > In short: we have the per-cpu fast counters, plus the slow counter > which is only used when cpu_hotplug_begin() is in progress. > > Oleg. >
get_online_cpus() in your code is still read-preference. I wish we quit this ability of get_online_cpus().
Lai.
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