svn commit: r291569 - head/sys/dev/sfxge

[Andrew Rybchenko]

Author: arybchik
Date: Tue Dec  1 06:23:15 2015
New Revision: 291569
URL: https://svnweb.freebsd.org/changeset/base/291569

Log:
  sfxge: avoid TSO packets collapses if packet header uses 2 segments
  
  It is really observed in the case of VLAN over sfxge interface.
  Also this change makes total value equal to 35 which is default assumed
  by the kernel for if_hw_tsomaxsegcount.
  
  Sponsored by:   Solarflare Communications, Inc.
  MFC after:      2 days
  Differential Revision: https://reviews.freebsd.org/D4319

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

Modified: head/sys/dev/sfxge/sfxge_tx.h
==============================================================================
--- head/sys/dev/sfxge/sfxge_tx.h	Tue Dec  1 06:22:27 2015	(r291568)
+++ head/sys/dev/sfxge/sfxge_tx.h	Tue Dec  1 06:23:15 2015	(r291569)
@@ -53,11 +53,13 @@
  * TSO, the mbuf length may be just over 64K, divided into 2K mbuf
  * clusters taking into account that the first may be not 2K cluster
  * boundary aligned.
+ * Packet header may be split into two segments because of, for example,
+ * VLAN header insertion.
  * The chain could be longer than this initially, but can be shortened
  * with m_collapse().
  */
 #define	SFXGE_TX_MAPPING_MAX_SEG					\
-	(1 + howmany(SFXGE_TSO_MAX_SIZE, MCLBYTES) + 1)
+	(2 + howmany(SFXGE_TSO_MAX_SIZE, MCLBYTES) + 1)
 
 /*
  * Buffer mapping flags.