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MFC: 279094

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sfxge: more accurate calculation of maximum number of TSO segments

Sponsored by:   Solarflare Communications, Inc.
Approved by:    gnn (mentor)
This commit is contained in:
arybchik 2015-03-25 10:59:24 +00:00
parent 4f836db713
commit db246d0cee
2 changed files with 14 additions and 4 deletions
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6
sys/dev/sfxge/sfxge_tx.c
View File

@ -72,10 +72,10 @@ __FBSDID("$FreeBSD$");
* maximum mbuf length we might need more than a ring-ful of
* descriptors, but this should not happen in practice except
* due to deliberate attack. In that case we will truncate
* the output at a packet boundary. Allow for a reasonable
* minimum MSS of 512.
* the output at a packet boundary.
*/
#define SFXGE_TSO_MAX_DESC ((65535 / 512) * 2 + SFXGE_TX_MAPPING_MAX_SEG - 1)
#define SFXGE_TSO_MAX_DESC \
(SFXGE_TSO_MAX_SEGS * 2 + SFXGE_TX_MAPPING_MAX_SEG - 1)
#define SFXGE_TXQ_BLOCK_LEVEL(_entries) ((_entries) - SFXGE_TSO_MAX_DESC)
#ifdef SFXGE_HAVE_MQ

12
sys/dev/sfxge/sfxge_tx.h
View File

@ -36,12 +36,22 @@
#include <netinet/ip.h>
#include <netinet/tcp.h>
/* Maximum size of TSO packet */
#define SFXGE_TSO_MAX_SIZE (65535)
/*
* Maximum number of segments to be created for a TSO packet.
* Allow for a reasonable minimum MSS of 512.
*/
#define SFXGE_TSO_MAX_SEGS howmany(SFXGE_TSO_MAX_SIZE, 512)
/* Maximum number of DMA segments needed to map an mbuf chain. With
* TSO, the mbuf length may be just over 64K, divided into 2K mbuf
* clusters. (The chain could be longer than this initially, but can
* be shortened with m_collapse().)
*/
#define SFXGE_TX_MAPPING_MAX_SEG (64 / 2 + 1)
#define SFXGE_TX_MAPPING_MAX_SEG \
(1 + howmany(SFXGE_TSO_MAX_SIZE, MCLBYTES))
/*
* Buffer mapping flags.