The words say: ... 230 @max_active: 231 232 @max_active determines the maximum number of execution contexts per 233 CPU which can be assigned to the work items of a wq. For example, 234 with @max_active of 16, at most 16 work items of the wq can be 235 executing at the same time per CPU. 236 237 Currently, for a bound wq, the maximum limit for @max_active is 512 238 and the default value used when 0 is specified is 256. For an unbound 239 wq, the limit is higher of 512 and 4 * num_possible_cpus(). These 240 values are chosen sufficiently high such that they are not the 241 limiting factor while providing protection in runaway cases. 242 243 The number of active work items of a wq is usually regulated by the 244 users of the wq, more specifically, by how many work items the users 245 may queue at the same time. Unless there is a specific need for 246 throttling the number of active work items, specifying '0' is 247 recommended. 248 249 Some users depend on the strict execution ordering of ST wq. The 250 combination of @max_active of 1 and WQ_UNBOUND is used to achieve this 251 behavior. Work items on such wq are always queued to the unbound 252 worker-pools and only one work item can be active at any given time thus 253 achieving the same ordering property as ST wq. And through http://lxr.oss.org.cn/search?string=alloc_workqueue, we can see that most used the default length config. -- Regards, shhuiw At 2014-07-09 07:45:00, "Robert Clove" <cloverobert@gmail.com> wrote: Thanks for the reply ... Can you state one more thing is there any limitation on size of queue in kernel? Regards Clove On Sat, Jul 5, 2014 at 4:32 PM, shhuiw <shhuiw@163.com> wrote: Hope this article can help: kernel-src/Documentation/workqueue.txt At 2014-07-04 04:34:03, "Freeman Zhang" <freeman.zhang1992@gmail.com> wrote: Hi, On 2014-07-04 13:50, Robert Clove wrote: Hi All, How we create queues in kernel space and what are the size limit ? Regards That should be kfifo. Check this: http://thelinuxdesk.com/tag/linux-kernel-queue/ Hope this can help :D All the best! Freeman