Author: andre
Date: Sat Aug 24 20:26:41 2013
New Revision: 254807
URL: http://svnweb.freebsd.org/changeset/base/254807
Log:
Compact m_hdr by packing the type and flags fields into one uint32_t.
The mbuf type is an enumerator with only a handful of types in use and
thus reduced from int to 8bits allowing for 255 types to be specified.
Only 5 types have been in use for a long time.
The flags field gets the remaining 24 bits with 12 bits for global
persistent flags and 12 bits for protocol/layer specific overlays.
Some of the global flags/functionality can be moved to the csum_flags
or ext_flags bits in the future.
MT_VENDOR[1-4] and MT_EXP[1-4] types for vendor-internal and
experimental local mapping are added.
The size of m_hdr shrinks from 24/40 to 20/32bytes (32/64bit architectures).
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/sys/mbuf.h
Modified: head/sys/sys/mbuf.h
==============================================================================
--- head/sys/sys/mbuf.h Sat Aug 24 20:06:00 2013 (r254806)
+++ head/sys/sys/mbuf.h Sat Aug 24 20:26:41 2013 (r254807)
@@ -82,23 +82,18 @@ struct mb_args {
};
#endif /* _KERNEL */
-#if defined(__LP64__)
-#define M_HDR_PAD 6
-#else
-#define M_HDR_PAD 2
-#endif
-
/*
* Header present at the beginning of every mbuf.
+ * Size ILP32: 20
+ * LP64: 32
*/
struct m_hdr {
struct mbuf *mh_next; /* next buffer in chain */
struct mbuf *mh_nextpkt; /* next chain in queue/record */
caddr_t mh_data; /* location of data */
- int mh_len; /* amount of data in this mbuf */
- int mh_flags; /* flags; see below */
- short mh_type; /* type of data in this mbuf */
- uint8_t pad[M_HDR_PAD];/* word align */
+ int32_t mh_len; /* amount of data in this mbuf */
+ uint32_t mh_type:8, /* type of data in this mbuf */
+ mh_flags:24; /* flags; see below */
};
/*
@@ -206,7 +201,10 @@ struct mbuf {
#define m_dat M_dat.M_databuf
/*
- * mbuf flags.
+ * mbuf flags of global significance and layer crossing.
+ * Those of only protocol/layer specific significance are to be mapped
+ * to M_PROTO[1-12] and cleared at layer handoff boundaries.
+ * NB: Limited to the lower 24 bits.
*/
#define M_EXT 0x00000001 /* has associated external storage */
#define M_PKTHDR 0x00000002 /* start of record */
@@ -430,12 +428,24 @@ struct mbuf {
#define CSUM_FRAGMENT 0x0 /* Unused */
/*
- * mbuf types.
+ * mbuf types describing the content of the mbuf (including external storage).
*/
#define MT_NOTMBUF 0 /* USED INTERNALLY ONLY! Object is not
mbuf */
#define MT_DATA 1 /* dynamic (data) allocation */
#define MT_HEADER MT_DATA /* packet header, use M_PKTHDR instead
*/
+
+#define MT_VENDOR1 4 /* for vendor-internal use */
+#define MT_VENDOR2 5 /* for vendor-internal use */
+#define MT_VENDOR3 6 /* for vendor-internal use */
+#define MT_VENDOR4 7 /* for vendor-internal use */
+
#define MT_SONAME 8 /* socket name */
+
+#define MT_EXP1 9 /* for experimental use */
+#define MT_EXP2 10 /* for experimental use */
+#define MT_EXP3 11 /* for experimental use */
+#define MT_EXP4 12 /* for experimental use */
+
#define MT_CONTROL 14 /* extra-data protocol message */
#define MT_OOBDATA 15 /* expedited data */
#define MT_NTYPES 16 /* number of mbuf types for mbtypes[] */
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