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Date:      Mon, 5 Oct 2020 18:49:55 +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: r366458 - stable/12/sys/dev/cxgbe
Message-ID:  <202010051849.095IntW9018109@repo.freebsd.org>
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Author: np
Date: Mon Oct  5 18:49:55 2020
New Revision: 366458
URL: https://svnweb.freebsd.org/changeset/base/366458

Log:
  MFC r366245:
  
  cxgbe(4): adjust the doorbell threshold for netmap freelists to match the
  maximum burst size used when fetching descriptors from the list.
  
  Sponsored by:	Chelsio Communications

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

Modified: stable/12/sys/dev/cxgbe/adapter.h
==============================================================================
--- stable/12/sys/dev/cxgbe/adapter.h	Mon Oct  5 18:47:12 2020	(r366457)
+++ stable/12/sys/dev/cxgbe/adapter.h	Mon Oct  5 18:49:55 2020	(r366458)
@@ -716,6 +716,7 @@ struct sge_nm_rxq {
 	uint32_t fl_sidx2;	/* copy of fl_sidx */
 	uint32_t fl_db_val;
 	u_int fl_db_saved;
+	u_int fl_db_threshold;	/* in descriptors */
 	u_int fl_hwidx:4;
 
 	/*

Modified: stable/12/sys/dev/cxgbe/t4_netmap.c
==============================================================================
--- stable/12/sys/dev/cxgbe/t4_netmap.c	Mon Oct  5 18:47:12 2020	(r366457)
+++ stable/12/sys/dev/cxgbe/t4_netmap.c	Mon Oct  5 18:49:55 2020	(r366458)
@@ -196,6 +196,9 @@ alloc_nm_rxq_hwq(struct vi_info *vi, struct sge_nm_rxq
 
 	nm_rxq->fl_cntxt_id = be16toh(c.fl0id);
 	nm_rxq->fl_pidx = nm_rxq->fl_cidx = 0;
+	nm_rxq->fl_db_saved = 0;
+	/* matches the X_FETCHBURSTMAX_512B or X_FETCHBURSTMAX_256B above. */
+	nm_rxq->fl_db_threshold = chip_id(sc) <= CHELSIO_T5 ? 8 : 4;
 	MPASS(nm_rxq->fl_sidx == na->num_rx_desc);
 	cntxt_id = nm_rxq->fl_cntxt_id - sc->sge.eq_start;
 	if (cntxt_id >= sc->sge.neq) {
@@ -1063,7 +1066,7 @@ cxgbe_netmap_rxsync(struct netmap_kring *kring, int fl
 				fl_pidx = 0;
 				slot = &ring->slot[0];
 			}
-			if (++dbinc == 8 && n >= 32) {
+			if (++dbinc == nm_rxq->fl_db_threshold) {
 				wmb();
 				if (starve_fl)
 					nm_rxq->fl_db_saved += dbinc;

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