On 8/16/14, Jens Axboe <axboe@xxxxxxxxx> wrote: > On 08/15/2014 10:36 AM, Jens Axboe wrote: >> On 08/15/2014 10:31 AM, Christoph Hellwig wrote: >>>> +static void loop_queue_work(struct work_struct *work) >>> >>> Offloading work straight to a workqueue dosn't make much sense >>> in the blk-mq model as we'll usually be called from one. If you >>> need to avoid the cases where we are called directly a flag for >>> the blk-mq code to always schedule a workqueue sounds like a much >>> better plan. >> >> That's a good point - would clean up this bit, and be pretty close to a >> one-liner to support in blk-mq for the drivers that always need blocking >> context. > > Something like this should do the trick - totally untested. But with > that, loop would just need to add BLK_MQ_F_WQ_CONTEXT to it's tag set > flags and it could always do the work inline from ->queue_rq(). I think it is a good idea. But for loop, there may be two problems: - default max_active for bound workqueue is 256, which means several slow loop devices might slow down whole block system. With kernel AIO, it won't be a big deal, but some block/fs may not support direct I/O and still fallback to workqueue - 6. Guidelines of Documentation/workqueue.txt If there is dependency among multiple work items used during memory reclaim, they should be queued to separate wq each with WQ_MEM_RECLAIM. Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
