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Date:      Sat, 22 Mar 2014 18:24:45 +0000 (UTC)
From:      Gleb Smirnoff <glebius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r263649 - head/sys/dev/sfxge
Message-ID:  <201403221824.s2MIOjq8042539@svn.freebsd.org>
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Author: glebius
Date: Sat Mar 22 18:24:44 2014
New Revision: 263649
URL: http://svnweb.freebsd.org/changeset/base/263649

Log:
  sfxge: limit software Tx queue size.
  
  Previous implementation limits put queue size only (when Tx lock can't
  be acquired), but get queue may grow unboundedly which results in mbuf
  pools exhaustion and latency growth.
  
  Submitted by:	Andrew Rybchenko <Andrew.Rybchenko at oktetlabs.ru>
  Sponsored by:	Solarflare Communications, Inc.

Modified:
  head/sys/dev/sfxge/sfxge_tx.c
  head/sys/dev/sfxge/sfxge_tx.h

Modified: head/sys/dev/sfxge/sfxge_tx.c
==============================================================================
--- head/sys/dev/sfxge/sfxge_tx.c	Sat Mar 22 17:28:14 2014	(r263648)
+++ head/sys/dev/sfxge/sfxge_tx.c	Sat Mar 22 18:24:44 2014	(r263649)
@@ -461,6 +461,9 @@ sfxge_tx_qdpl_put(struct sfxge_txq *txq,
 
 		sfxge_tx_qdpl_swizzle(txq);
 
+		if (stdp->std_count >= SFXGE_TX_DPL_GET_PKT_LIMIT_DEFAULT)
+			return (ENOBUFS);
+
 		*(stdp->std_getp) = mbuf;
 		stdp->std_getp = &mbuf->m_nextpkt;
 		stdp->std_count++;
@@ -480,8 +483,8 @@ sfxge_tx_qdpl_put(struct sfxge_txq *txq,
 				old_len = mp->m_pkthdr.csum_data;
 			} else
 				old_len = 0;
-			if (old_len >= SFXGE_TX_MAX_DEFERRED)
-				return ENOBUFS;
+			if (old_len >= SFXGE_TX_DPL_PUT_PKT_LIMIT_DEFAULT)
+				return (ENOBUFS);
 			mbuf->m_pkthdr.csum_data = old_len + 1;
 			mbuf->m_nextpkt = (void *)old;
 		} while (atomic_cmpset_ptr(putp, old, new) == 0);
@@ -512,12 +515,9 @@ sfxge_tx_packet_add(struct sfxge_txq *tx
 	 */
 	locked = mtx_trylock(&txq->lock);
 
-	/*
-	 * Can only fail if we weren't able to get the lock.
-	 */
 	if (sfxge_tx_qdpl_put(txq, m, locked) != 0) {
-		KASSERT(!locked,
-		    ("sfxge_tx_qdpl_put() failed locked"));
+		if (locked)
+			mtx_unlock(&txq->lock);
 		rc = ENOBUFS;
 		goto fail;
 	}

Modified: head/sys/dev/sfxge/sfxge_tx.h
==============================================================================
--- head/sys/dev/sfxge/sfxge_tx.h	Sat Mar 22 17:28:14 2014	(r263648)
+++ head/sys/dev/sfxge/sfxge_tx.h	Sat Mar 22 18:24:44 2014	(r263649)
@@ -75,7 +75,8 @@ struct sfxge_tx_mapping {
 	enum sfxge_tx_buf_flags	flags;
 };
 
-#define SFXGE_TX_MAX_DEFERRED 64
+#define	SFXGE_TX_DPL_GET_PKT_LIMIT_DEFAULT	64
+#define	SFXGE_TX_DPL_PUT_PKT_LIMIT_DEFAULT	64
 
 /*
  * Deferred packet list.

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