Commit Graph

15 Commits

Author SHA1 Message Date
Alan Somers
1b82e02f4d Add bit_count to the bitstring(3) api
Add a bit_count function, which efficiently counts the number of bits set in
a bitstring.

sys/sys/bitstring.h
tests/sys/sys/bitstring_test.c
share/man/man3/bitstring.3
	Add bit_alloc

sys/kern/subr_unit.c
	Use bit_count instead of a naive counting loop in check_unrhdr, used
	when INVARIANTS are enabled. The userland test runs about 6x faster
	in a generic build, or 8.5x faster when built for Nehalem, which has
	the POPCNT instruction.

sys/sys/param.h
	Bump __FreeBSD_version due to the addition of bit_alloc

UPDATING
	Add a note about the ABI incompatibility of the bitstring(3)
	changes, as suggested by lidl.

Suggested by:	gibbs
Reviewed by:	gibbs, ngie
MFC after:	9 days
X-MFC-With:	299090, 300538
Relnotes:	yes
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D6255
2016-05-23 20:29:18 +00:00
Alan Somers
8907f744ff Improve performance and functionality of the bitstring(3) api
Two new functions are provided, bit_ffs_at() and bit_ffc_at(), which allow
for efficient searching of set or cleared bits starting from any bit offset
within the bit string.

Performance is improved by operating on longs instead of bytes and using
ffsl() for searches within a long. ffsl() is a compiler builtin in both
clang and gcc for most architectures, converting what was a brute force
while loop search into a couple of instructions.

All of the bitstring(3) API continues to be contained in the header file.
Some of the functions are large enough that perhaps they should be uninlined
and moved to a library, but that is beyond the scope of this commit.

sys/sys/bitstring.h:
        Convert the majority of the existing bit string implementation from
        macros to inline functions.

        Properly protect the implementation from inadvertant macro expansion
        when included in a user's program by prefixing all private
        macros/functions and local variables with '_'.

        Add bit_ffs_at() and bit_ffc_at(). Implement bit_ffs() and
        bit_ffc() in terms of their "at" counterparts.

        Provide a kernel implementation of bit_alloc(), making the full API
        usable in the kernel.

        Improve code documenation.

share/man/man3/bitstring.3:
        Add pre-exisiting API bit_ffc() to the synopsis.

        Document new APIs.

        Document the initialization state of the bit strings
        allocated/declared by bit_alloc() and bit_decl().

        Correct documentation for bitstr_size(). The original code comments
        indicate the size is in bytes, not "elements of bitstr_t". The new
        implementation follows this lead. Only hastd assumed "elements"
        rather than bytes and it has been corrected.

etc/mtree/BSD.tests.dist:
tests/sys/Makefile:
tests/sys/sys/Makefile:
tests/sys/sys/bitstring.c:
        Add tests for all existing and new functionality.

include/bitstring.h
	Include all headers needed by sys/bitstring.h

lib/libbluetooth/bluetooth.h:
usr.sbin/bluetooth/hccontrol/le.c:
        Include bitstring.h instead of sys/bitstring.h.

sbin/hastd/activemap.c:
        Correct usage of bitstr_size().

sys/dev/xen/blkback/blkback.c
        Use new bit_alloc.

sys/kern/subr_unit.c:
        Remove hard-coded assumption that sizeof(bitstr_t) is 1.  Get rid of
        unrb.busy, which caches the number of bits set in unrb.map.  When
        INVARIANTS are disabled, nothing needs to know that information.
        callapse_unr can be adapted to use bit_ffs and bit_ffc instead.
        Eliminating unrb.busy saves memory, simplifies the code, and
        provides a slight speedup when INVARIANTS are disabled.

sys/net/flowtable.c:
        Use the new kernel implementation of bit-alloc, instead of hacking
        the old libc-dependent macro.

sys/sys/param.h
        Update __FreeBSD_version to indicate availability of new API

Submitted by:   gibbs, asomers
Reviewed by:    gibbs, ngie
MFC after:      4 weeks
Sponsored by:   Spectra Logic Corp
Differential Revision:  https://reviews.freebsd.org/D6004
2016-05-04 22:34:11 +00:00
Conrad Meyer
7ebf41220c Document bitset(9) 2015-10-17 19:55:58 +00:00
Eitan Adler
dda5b39711 multiple: Remove 3rd clause from BSD license where approved by the
regents and renumber.

This patch skips files in contrib/ and crypto/

Acked by:	imp
Discussed with:	emaste
2014-03-14 03:07:51 +00:00
Ruslan Ermilov
32eef9aeb1 mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00
Ruslan Ermilov
3d45e180f4 mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 15:31:11 +00:00
Ruslan Ermilov
d0353b836e mdoc(7) police: split punctuation characters + misc fixes. 2001-02-01 16:38:02 +00:00
Ruslan Ermilov
3136363f3e Prepare for mdoc(7)NG. 2000-12-29 09:18:45 +00:00
Ruslan Ermilov
251c176f41 mdoc(7) police: use certified section headers wherever possible. 2000-11-17 11:44:16 +00:00
Peter Wemm
7f3dea244c $Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00
John-Mark Gurney
0b60724004 fix the links to the bitstring man page..
fix wording in man page, through != to
1999-06-25 04:51:49 +00:00
Bruce Evans
69a6a1d797 Fixed type bugs in synopsis. Some of the typedefs that were used here
haven't existed for years, if they ever existed.  The "prototypes" are
actually for macros, so they are difficult to check automatically.
1997-04-13 14:19:59 +00:00
John-Mark Gurney
ac5afce161 add missing cvs Id lines. 1997-03-07 03:28:23 +00:00
Mike Pritchard
21421932f5 Use the .Bx macro where appropriate. 1996-08-22 23:39:32 +00:00
Rodney W. Grimes
afe61c1516 BSD 4.4 Lite Share Sources 1994-05-30 19:09:18 +00:00