Commit 6e94e7fd authored by Yankun Li's avatar Yankun Li Committed by Tomasz Zawadzki
Browse files

lib/reduce: merge consecutive IO requests 



if chunk_size is 16KB, backing_io_unit is 4KB, when reading
or writing a 16kb of data, it is split into four small IO
requests.
In this patch, if the access area is adjacent, the small IO
is combined into a single IO request, reducing IO latency.

Change-Id: Id8c91854679fcb7f1706a3314dbbe168b4d4f501
Signed-off-by: default avatarYankun Li <845245370@qq.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/23970


Reviewed-by: default avatarJim Harris <jim.harris@samsung.com>
Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarAleksey Marchuk <alexeymar@nvidia.com>
Community-CI: Mellanox Build Bot
parent dfaa72f9

lib/reduce/reduce.c

+80 −2
Original line number Diff line number Diff line
@@ -1068,8 +1068,13 @@ _write_write_done(void *_req, int reduce_errno) 
	_reduce_vol_complete_req(req, 0);

}



struct reduce_merged_io_desc {

	uint64_t io_unit_index;

	uint32_t num_io_units;

};



static void

_issue_backing_ops(struct spdk_reduce_vol_request *req, struct spdk_reduce_vol *vol,

_issue_backing_ops_without_merge(struct spdk_reduce_vol_request *req, struct spdk_reduce_vol *vol,

				 reduce_request_fn next_fn, bool is_write)

{

	struct iovec *iov;
@@ -1102,6 +1107,79 @@ _issue_backing_ops(struct spdk_reduce_vol_request *req, struct spdk_reduce_vol * 
	}

}



static void

_issue_backing_ops(struct spdk_reduce_vol_request *req, struct spdk_reduce_vol *vol,

		   reduce_request_fn next_fn, bool is_write)

{

	struct iovec *iov;

	struct reduce_merged_io_desc merged_io_desc[4];

	uint8_t *buf;

	bool merge = false;

	uint32_t num_io = 0;

	uint32_t io_unit_counts = 0;

	uint32_t merged_io_idx = 0;

	uint32_t i;



	/* The merged_io_desc value is defined here to contain four elements,

	 * and the chunk size must be four times the maximum of the io unit.

	 * if chunk size is too big, don't merge IO.

	 */

	if (vol->backing_io_units_per_chunk > 4) {

		_issue_backing_ops_without_merge(req, vol, next_fn, is_write);

		return;

	}



	if (req->chunk_is_compressed) {

		iov = req->comp_buf_iov;

		buf = req->comp_buf;

	} else {

		iov = req->decomp_buf_iov;

		buf = req->decomp_buf;

	}



	for (i = 0; i < req->num_io_units; i++) {

		if (!merge) {

			merged_io_desc[merged_io_idx].io_unit_index = req->chunk->io_unit_index[i];

			merged_io_desc[merged_io_idx].num_io_units = 1;

			num_io++;

		}



		if (i + 1 == req->num_io_units) {

			break;

		}



		if (req->chunk->io_unit_index[i] + 1 == req->chunk->io_unit_index[i + 1]) {

			merged_io_desc[merged_io_idx].num_io_units += 1;

			merge = true;

			continue;

		}

		merge = false;

		merged_io_idx++;

	}



	req->num_backing_ops = num_io;

	req->backing_cb_args.cb_fn = next_fn;

	req->backing_cb_args.cb_arg = req;

	for (i = 0; i < num_io; i++) {

		iov[i].iov_base = buf + io_unit_counts * vol->params.backing_io_unit_size;

		iov[i].iov_len = vol->params.backing_io_unit_size * merged_io_desc[i].num_io_units;

		if (is_write) {

			vol->backing_dev->writev(vol->backing_dev, &iov[i], 1,

						 merged_io_desc[i].io_unit_index * vol->backing_lba_per_io_unit,

						 vol->backing_lba_per_io_unit * merged_io_desc[i].num_io_units,

						 &req->backing_cb_args);

		} else {

			vol->backing_dev->readv(vol->backing_dev, &iov[i], 1,

						merged_io_desc[i].io_unit_index * vol->backing_lba_per_io_unit,

						vol->backing_lba_per_io_unit * merged_io_desc[i].num_io_units,

						&req->backing_cb_args);

		}



		/* Collects the number of processed I/O. */

		io_unit_counts += merged_io_desc[i].num_io_units;

	}

}



static void

_reduce_vol_write_chunk(struct spdk_reduce_vol_request *req, reduce_request_fn next_fn,

			uint32_t compressed_size)