2012/8/14 Tejun Heo <t...@kernel.org>: > Hello, > > On Tue, Aug 14, 2012 at 01:17:49AM +0900, Joonsoo Kim wrote: >> We assign cpu id into work struct in queue_delayed_work_on(). >> In current implementation, when work is come in first time, >> current running cpu id is assigned. >> If we do queue_delayed_work_on() with CPU A on CPU B, >> __queue_work() invoked in delayed_work_timer_fn() go into sub-optimal path >> in case of WQ_NON_REENTRANT. >> Change it to cpu argument is prevent to go into sub-optimal path. > > Which part is suboptimal? Also, what if @cpu is WQ_UNBOUND?
Hi. I think a following scenario. wq = WQ_NON_REENTRANT. queue_delayed_work_on(CPU B) is invoked in CPU A, so lcpu = CPU A, cpu = CPU B. In this case, we call add_time_on(CPU B), then delayed_work_timer_fn() is invoked on CPU B. delayed_work_timer_fn() calls __queue_work(), then following comparisons return true! gcwq = get_gcwq(cpu); if (wq->flags & WQ_NON_REENTRANT && (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) { I thinks that if we assign cpu to lcpu, above comparisons return false, so save some overheads. Is there any missing part? And, do u mean @cpu is WORK_CPU_UNBOUND? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/