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Commit ade6f8af authored by Sebastian Sanchez's avatar Sebastian Sanchez Committed by Doug Ledford
Browse files

IB/hfi1: Get rid of divide when setting the tx request header 



Div instructions show costly in profiles when
the tx request header is set. Using right shift
instead of a divide operation reduces the cycles
spent in the function that sets the tx request
header as shown in the profile. Use right shift
operation instead.

Profile before change:
43.24%  009
|
|--23.41%-- user_sdma_send_pkts
|          |
|          |--99.90%-- hfi1_user_sdma_process_requestAfter:

Profile after change:
45.75%  009
|
|--14.81%-- user_sdma_send_pkts
|          |
|          |--99.95%-- hfi1_user_sdma_process_request

Reviewed-by: default avatarMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: default avatarSebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent dd1ed108

drivers/infiniband/hw/hfi1/user_sdma.c

+17 −17
Original line number Diff line number Diff line
@@ -143,7 +143,9 @@ MODULE_PARM_DESC(sdma_comp_size, "Size of User SDMA completion ring. Default: 12 


/* KDETH OM multipliers and switch over point */

#define KDETH_OM_SMALL     4

#define KDETH_OM_SMALL_SHIFT     2

#define KDETH_OM_LARGE     64

#define KDETH_OM_LARGE_SHIFT     6

#define KDETH_OM_MAX_SIZE  (1 << ((KDETH_OM_LARGE / KDETH_OM_SMALL) + 1))



/* Tx request flag bits */
@@ -228,12 +230,6 @@ struct user_sdma_request { 
	 * size of the TID entry.

	 */

	u32 tidoffset;

	/*

	 * KDETH.OM

	 * Remember this because the header template always sets it

	 * to 0.

	 */

	u8 omfactor;

	/*

	 * We copy the iovs for this request (based on

	 * info.iovcnt). These are only the data vectors
@@ -1323,6 +1319,7 @@ static int set_txreq_header(struct user_sdma_request *req, 
{

	struct hfi1_user_sdma_pkt_q *pq = req->pq;

	struct hfi1_pkt_header *hdr = &tx->hdr;

	u8 omfactor; /* KDETH.OM */

	u16 pbclen;

	int ret;

	u32 tidval = 0, lrhlen = get_lrh_len(*hdr, pad_len(datalen));
@@ -1400,8 +1397,9 @@ static int set_txreq_header(struct user_sdma_request *req, 
			}

			tidval = req->tids[req->tididx];

		}

		req->omfactor = EXP_TID_GET(tidval, LEN) * PAGE_SIZE >=

			KDETH_OM_MAX_SIZE ? KDETH_OM_LARGE : KDETH_OM_SMALL;

		omfactor = EXP_TID_GET(tidval, LEN) * PAGE_SIZE >=

			KDETH_OM_MAX_SIZE ? KDETH_OM_LARGE_SHIFT :

			KDETH_OM_SMALL_SHIFT;

		/* Set KDETH.TIDCtrl based on value for this TID. */

		KDETH_SET(hdr->kdeth.ver_tid_offset, TIDCTRL,

			  EXP_TID_GET(tidval, CTRL));
@@ -1416,12 +1414,12 @@ static int set_txreq_header(struct user_sdma_request *req, 
		 * transfer.

		 */

		SDMA_DBG(req, "TID offset %ubytes %uunits om%u",

			 req->tidoffset, req->tidoffset / req->omfactor,

			 req->omfactor != KDETH_OM_SMALL);

			 req->tidoffset, req->tidoffset >> omfactor,

			 omfactor != KDETH_OM_SMALL_SHIFT);

		KDETH_SET(hdr->kdeth.ver_tid_offset, OFFSET,

			  req->tidoffset / req->omfactor);

			  req->tidoffset >> omfactor);

		KDETH_SET(hdr->kdeth.ver_tid_offset, OM,

			  req->omfactor != KDETH_OM_SMALL);

			  omfactor != KDETH_OM_SMALL_SHIFT);

	}

done:

	trace_hfi1_sdma_user_header(pq->dd, pq->ctxt, pq->subctxt,
@@ -1433,6 +1431,7 @@ static int set_txreq_header_ahg(struct user_sdma_request *req, 
				struct user_sdma_txreq *tx, u32 len)

{

	int diff = 0;

	u8 omfactor; /* KDETH.OM */

	struct hfi1_user_sdma_pkt_q *pq = req->pq;

	struct hfi1_pkt_header *hdr = &req->hdr;

	u16 pbclen = le16_to_cpu(hdr->pbc[0]);
@@ -1484,14 +1483,15 @@ static int set_txreq_header_ahg(struct user_sdma_request *req, 
			}

			tidval = req->tids[req->tididx];

		}

		req->omfactor = ((EXP_TID_GET(tidval, LEN) *

		omfactor = ((EXP_TID_GET(tidval, LEN) *

				  PAGE_SIZE) >=

				 KDETH_OM_MAX_SIZE) ? KDETH_OM_LARGE :

			KDETH_OM_SMALL;

				 KDETH_OM_MAX_SIZE) ? KDETH_OM_LARGE_SHIFT :

				 KDETH_OM_SMALL_SHIFT;

		/* KDETH.OM and KDETH.OFFSET (TID) */

		AHG_HEADER_SET(req->ahg, diff, 7, 0, 16,

			       ((!!(req->omfactor - KDETH_OM_SMALL)) << 15 |

				((req->tidoffset / req->omfactor) & 0x7fff)));

			       ((!!(omfactor - KDETH_OM_SMALL_SHIFT)) << 15 |

				((req->tidoffset >> omfactor)

				 & 0x7fff)));

		/* KDETH.TIDCtrl, KDETH.TID, KDETH.Intr, KDETH.SH */

		val = cpu_to_le16(((EXP_TID_GET(tidval, CTRL) & 0x3) << 10) |

				   (EXP_TID_GET(tidval, IDX) & 0x3ff));