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Date:      Fri, 27 Mar 2020 03:58:01 +0000 (UTC)
From:      Navdeep Parhar <np@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r359351 - stable/12/sys/dev/cxgbe
Message-ID:  <202003270358.02R3w1FG088072@repo.freebsd.org>
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Author: np
Date: Fri Mar 27 03:58:00 2020
New Revision: 359351
URL: https://svnweb.freebsd.org/changeset/base/359351

Log:
  MFC r359159:
  
  cxgbe(4): Split sge_nm_rxq into three cachelines.
  
  This reduces the lines bouncing around between the driver rx ithread and
  the netmap rxsync thread.  There is no net change in the size of the
  struct (it continues to waste a lot of space).
  
  This kind of split was originally proposed in D17869 by Marc De La
  Gueronniere @ Verisign, Inc.
  
  Sponsored by:	Chelsio Communications

Modified:
  stable/12/sys/dev/cxgbe/adapter.h
  stable/12/sys/dev/cxgbe/t4_netmap.c
  stable/12/sys/dev/cxgbe/t4_sge.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/dev/cxgbe/adapter.h
==============================================================================
--- stable/12/sys/dev/cxgbe/adapter.h	Fri Mar 27 03:18:52 2020	(r359350)
+++ stable/12/sys/dev/cxgbe/adapter.h	Fri Mar 27 03:58:00 2020	(r359351)
@@ -677,7 +677,9 @@ struct sge_wrq {
 
 #define INVALID_NM_RXQ_CNTXT_ID ((uint16_t)(-1))
 struct sge_nm_rxq {
-	volatile int nm_state;	/* NM_OFF, NM_ON, or NM_BUSY */
+	/* Items used by the driver rx ithread are in this cacheline. */
+	volatile int nm_state __aligned(CACHE_LINE_SIZE);	/* NM_OFF, NM_ON, or NM_BUSY */
+	u_int nid;		/* netmap ring # for this queue */
 	struct vi_info *vi;
 
 	struct iq_desc *iq_desc;
@@ -686,20 +688,23 @@ struct sge_nm_rxq {
 	uint16_t iq_cidx;
 	uint16_t iq_sidx;
 	uint8_t iq_gen;
+	uint32_t fl_sidx;
 
-	__be64  *fl_desc;
+	/* Items used by netmap rxsync are in this cacheline. */
+	__be64  *fl_desc __aligned(CACHE_LINE_SIZE);
 	uint16_t fl_cntxt_id;
-	uint32_t fl_cidx;
 	uint32_t fl_pidx;
-	uint32_t fl_sidx;
+	uint32_t fl_sidx2;	/* copy of fl_sidx */
 	uint32_t fl_db_val;
+	u_int fl_db_saved;
 	u_int fl_hwidx:4;
 
-	u_int fl_db_saved;
-	u_int nid;		/* netmap ring # for this queue */
+	/*
+	 * fl_cidx is used by both the ithread and rxsync, the rest are not used
+	 * in the rx fast path.
+	 */
+	uint32_t fl_cidx __aligned(CACHE_LINE_SIZE);
 
-	/* infrequently used items after this */
-
 	bus_dma_tag_t iq_desc_tag;
 	bus_dmamap_t iq_desc_map;
 	bus_addr_t iq_ba;
@@ -708,7 +713,7 @@ struct sge_nm_rxq {
 	bus_dma_tag_t fl_desc_tag;
 	bus_dmamap_t fl_desc_map;
 	bus_addr_t fl_ba;
-} __aligned(CACHE_LINE_SIZE);
+};
 
 #define INVALID_NM_TXQ_CNTXT_ID ((u_int)(-1))
 struct sge_nm_txq {

Modified: stable/12/sys/dev/cxgbe/t4_netmap.c
==============================================================================
--- stable/12/sys/dev/cxgbe/t4_netmap.c	Fri Mar 27 03:18:52 2020	(r359350)
+++ stable/12/sys/dev/cxgbe/t4_netmap.c	Fri Mar 27 03:58:00 2020	(r359351)
@@ -916,7 +916,7 @@ cxgbe_netmap_rxsync(struct netmap_kring *kring, int fl
 		MPASS((n & 7) == 0);
 
 		IDXINCR(kring->nr_hwcur, n, kring->nkr_num_slots);
-		IDXINCR(nm_rxq->fl_pidx, n, nm_rxq->fl_sidx);
+		IDXINCR(nm_rxq->fl_pidx, n, nm_rxq->fl_sidx2);
 
 		while (n > 0) {
 			for (i = 0; i < 8; i++, fl_pidx++, slot++) {
@@ -924,10 +924,10 @@ cxgbe_netmap_rxsync(struct netmap_kring *kring, int fl
 				MPASS(ba != 0);
 				nm_rxq->fl_desc[fl_pidx] = htobe64(ba | hwidx);
 				slot->flags &= ~NS_BUF_CHANGED;
-				MPASS(fl_pidx <= nm_rxq->fl_sidx);
+				MPASS(fl_pidx <= nm_rxq->fl_sidx2);
 			}
 			n -= 8;
-			if (fl_pidx == nm_rxq->fl_sidx) {
+			if (fl_pidx == nm_rxq->fl_sidx2) {
 				fl_pidx = 0;
 				slot = &ring->slot[0];
 			}

Modified: stable/12/sys/dev/cxgbe/t4_sge.c
==============================================================================
--- stable/12/sys/dev/cxgbe/t4_sge.c	Fri Mar 27 03:18:52 2020	(r359350)
+++ stable/12/sys/dev/cxgbe/t4_sge.c	Fri Mar 27 03:58:00 2020	(r359351)
@@ -3587,6 +3587,7 @@ alloc_nm_rxq(struct vi_info *vi, struct sge_nm_rxq *nm
 	nm_rxq->iq_gen = F_RSPD_GEN;
 	nm_rxq->fl_pidx = nm_rxq->fl_cidx = 0;
 	nm_rxq->fl_sidx = na->num_rx_desc;
+	nm_rxq->fl_sidx2 = nm_rxq->fl_sidx;	/* copy for rxsync cacheline */
 	nm_rxq->intr_idx = intr_idx;
 	nm_rxq->iq_cntxt_id = INVALID_NM_RXQ_CNTXT_ID;

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