On 2023/9/16 17:23, Ming Lei wrote: > On Wed, Sep 13, 2023 at 03:16:12PM +0000, chengming.zhou@xxxxxxxxx wrote: >> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> >> >> There is a limit that batched queue_rqs() can't work on shared tags >> queue, since the account of active requests can't be done there. >> >> Now we account the active requests only in blk_mq_get_driver_tag(), >> which is not the time we get driver tag actually (with none elevator). >> >> To support batched queue_rqs() on shared tags queue, we move the >> account of active requests to where we get the driver tag: >> >> 1. none elevator: blk_mq_get_tags() and blk_mq_get_tag() >> 2. other elevator: __blk_mq_alloc_driver_tag() >> >> This is clearer and match with the unaccount side, which just happen >> when we put the driver tag. >> >> The other good point is that we don't need RQF_MQ_INFLIGHT trick >> anymore, which used to avoid double account of flush request. >> Now we only account when actually get the driver tag, so all is good. >> We will remove RQF_MQ_INFLIGHT in the next patch. > > RQF_MQ_INFLIGHT is only set for BLK_MQ_F_TAG_QUEUE_SHARED, so we can > avoid the extra atomic accounting for !BLK_MQ_F_TAG_QUEUE_SHARED. > > But now your patch switches to account unconditionally by removing > RQF_MQ_INFLIGHT, not friendly for !BLK_MQ_F_TAG_QUEUE_SHARED. > Hi Ming, blk_mq_add_active_requests() will check hctx->flags before doing atomic accounting and only account for BLK_MQ_F_TAG_QUEUE_SHARED. Yes, we don't need any atomic accounting in non-shared queue. Thanks.
