On Tue, Oct 12, 2021 at 12:17:39PM -0600, Jens Axboe wrote:
> Take advantage of struct io_batch, if passed in to the nvme poll handler.
> If it's set, rather than complete each request individually inline, store
> them in the io_batch list. We only do so for requests that will complete
> successfully, anything else will be completed inline as before.
>
> Add an mq_ops->complete_batch() handler to do the post-processing of
> the io_batch list once polling is complete.
>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> ---
> drivers/nvme/host/pci.c | 69 +++++++++++++++++++++++++++++++++++++----
> 1 file changed, 63 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 4ad63bb9f415..4713da708cd4 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -959,7 +959,7 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
> return ret;
> }
>
> -static void nvme_pci_complete_rq(struct request *req)
> +static void nvme_pci_unmap_rq(struct request *req)
> {
> struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
> struct nvme_dev *dev = iod->nvmeq->dev;
> @@ -969,9 +969,34 @@ static void nvme_pci_complete_rq(struct request *req)
> rq_integrity_vec(req)->bv_len, rq_data_dir(req));
> if (blk_rq_nr_phys_segments(req))
> nvme_unmap_data(dev, req);
> +}
> +
> +static void nvme_pci_complete_rq(struct request *req)
> +{
> + nvme_pci_unmap_rq(req);
> nvme_complete_rq(req);
> }
>
> +static void nvme_pci_complete_batch(struct io_batch *ib)
> +{
> + struct request *req;
> +
> + req = ib->req_list;
> + while (req) {
> + nvme_pci_unmap_rq(req);
> + if (req->rq_flags & RQF_SPECIAL_PAYLOAD)
> + nvme_cleanup_cmd(req);
> + if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> + req_op(req) == REQ_OP_ZONE_APPEND)
> + req->__sector = nvme_lba_to_sect(req->q->queuedata,
> + le64_to_cpu(nvme_req(req)->result.u64));
> + req->status = nvme_error_status(nvme_req(req)->status);
> + req = req->rq_next;
> + }
> +
> + blk_mq_end_request_batch(ib);
I hate all this open coding. All the common logic needs to be in a
common helper. Also please add a for_each macro for the request list
iteration. I already thought about that for the batch allocation in
for-next, but with ever more callers this becomes essential.
> + if (!nvme_try_complete_req(req, cqe->status, cqe->result)) {
> + enum nvme_disposition ret;
> +
> + ret = nvme_decide_disposition(req);
> + if (unlikely(!ib || req->end_io || ret != COMPLETE)) {
> + nvme_pci_complete_rq(req);
This actually is the likely case as only polling ever does the batch
completion. In doubt I'd prefer if we can avoid these likely/unlikely
annotations as much as possible.
> + } else {
> + req->rq_next = ib->req_list;
> + ib->req_list = req;
> + }
And all this list manipulation should use proper helper.
> + }
Also - can you look into turning this logic into an inline function with
a callback for the driver? I think in general gcc will avoid the
indirect call for function pointers passed directly. That way we can
keep a nice code structure but also avoid the indirections.
Same for nvme_pci_complete_batch.
