Traditionally the hcreate() function creates a hash table that uses
chaining, using a fixed user-provided size. The problem with this
approach is that this often either wastes memory (table too big) or
yields bad performance (table too small). For applications it may not
always be easy to estimate the right hash table size. A fixed number
only increases performance compared to a linked list by a constant
factor.
This problem can be solved easily by dynamically resizing the hash
table. If the size of the hash table is at least doubled, this has no
negative on the running time complexity. If a dynamically sized hash
table is used, we can also switch to using open addressing instead of
chaining, which has the advantage of just using a single allocation for
the entire table, instead of allocating many small objects.
Finally, a problem with the existing implementation is that its
deterministic algorithm for hashing makes it possible to come up with
fixed patterns to trigger an excessive number of collisions. We can
easily solve this by using FNV-1a as a hashing algorithm in combination
with a randomly generated offset basis.
Measurements have shown that this implementation is about 20-25% faster
than the existing implementation (even if the existing implementation is
given an excessive number of buckets). Though it allocates more memory
through malloc() than the old implementation (between 4-8 pointers per
used entry instead of 3), process memory use is similar to the old
implementation as if the estimated size was underestimated by a factor
10. This is due to the fact that malloc() needs to perform less
bookkeeping.
Reviewed by: jilles, pfg
Obtained from: https://github.com/NuxiNL/cloudlibc
Differential Revision: https://reviews.freebsd.org/D4644
Add a manpage for it, assign the copyright to the OpenBSD project on it since it
is mostly copy/paste from OpenBSD manpage.
style(9) fixes
Differential Revision: https://reviews.freebsd.org/D2420
Reviewed by: kib
While testing this I found a conformance issue in hdestroy()
that will be fixed in a subsequent commit.
Obtained from: NetBSD (hcreate.c, CVS Rev. 1.7)
if not already defined. This allows building libc from outside of
lib/libc using a reach-over makefile.
A typical use-case is to build a standard ILP32 version and a COMPAT32
version in a single iteration by building the COMPAT32 version using a
reach-over makefile.
Obtained from: Juniper Networks, Inc.
prior to 3.0.0 release) as contrib/jemalloc, and integrate it into libc.
The code being imported by this commit diverged from
lib/libc/stdlib/malloc.c in March 2010, which means that a portion of
the jemalloc 1.0.0 ChangeLog entries are relevant, as are the entries
for all subsequent releases.
The C11 folks reinvented the wheel by introducing an aligned version of
malloc(3) called aligned_alloc(3), instead of posix_memalign(3). Instead
of returning the allocation by reference, it returns the address, just
like malloc(3).
Reviewed by: jasone@
__noreturn macro and modify the other exiting functions to use it.
The __noreturn macro, unlike __dead2, must be used BEFORE the function.
This is in line with the C and C++ specifications that place _Noreturn (c1x)
and [[noreturn]] (C++11) in front of the functions. As with __dead2, this
macro falls back to using the GCC attribute.
Unfortunately, clang currently sets the same value for the C version macro
in C99 and C1x modes, so these functions are hidden by default. At some
point before 10.0, I need to go through the headers and clean up the C1x /
C++11 visibility.
Reviewed by: brooks (mentor)
-g, by reverting r219139. The LLVM PR referenced in that revision was
fixed in the mean time, and we imported a clang snapshot soon
afterwards, so the temporary workaround of disabling clang's integrated
assembler is no longer needed.
In this particular case, using e.g. DEBUG_FLAGS=-g causes clang to
output certain directives into assembly that our version of GNU as
chokes on.
Reported by: dougb
Approved by: re (kib)
kernel.debug (or possibly other files), when WITH_CTF is active.
This is caused by a bug in clang's integrated assembler, causing malloc
to sometimes hang during initialization in statically linked executables
that use threading, such as the copy of ctfmerge that is built during
the bootstrap stage of buildworld. The bug has been submitted upstream:
http://llvm.org/bugs/show_bug.cgi?id=9352
Note that you might have to rebuild and install libc first, to get your
kernel build to finish, because the ctfmerge binary built during
bootstrap is linked with your base system's copy of libc.a, which might
already contain a bad copy of malloc.o.
add a wrapper for it in libc and rework the code in libthr, the
system call still can return EINTR, we keep this feature.
Discussed on: thread
Reviewed by: jilles
their implementations aren't in the same files. Introduce LIBC_ARCH
and use that in preference to MACHINE_CPUARCH. Tested by amd64 and
powerpc64 builds (thanks nathanw@)
The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:
- Improved driver model:
The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.
If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.
- Improved hotplugging:
With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).
The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.
- Improved performance:
One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.
Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.
Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan
setenv(3) by tracking the size of the memory allocated instead of using
strlen() on the current value.
Convert all calls to POSIX from historic BSD API:
- unsetenv returns an int.
- putenv takes a char * instead of const char *.
- putenv no longer makes a copy of the input string.
- errno is set appropriately for POSIX. Exceptions involve bad environ
variable and internal initialization code. These both set errno to
EFAULT.
Several patches to base utilities to handle the POSIX changes from
Andrey Chernov's previous commit. A few I re-wrote to use setenv()
instead of putenv().
New regression module for tools/regression/environ to test these
functions. It also can be used to test the performance.
Bump __FreeBSD_version to 700050 due to API change.
PR: kern/99826
Approved by: wes
Approved by: re (kensmith)
* Add posix_memalign().
* Move calloc() from calloc.c to malloc.c. Add a calloc() implementation in
rtld-elf in order to make the loader happy (even though calloc() isn't
used in rtld-elf).
* Add _malloc_prefork() and _malloc_postfork(), and use them instead of
directly manipulating __malloc_lock.
Approved by: phk, markm (mentor)
between a 32-bit integer and a radix-64 ASCII string. The l64a_r() function
is a NetBSD addition.
PR: 51209 (based on submission, but very different)
Reviewed by: bde, ru
send strhash(3) off to sleep with the fishes. Nothing in our tree uses it.
It has no documentation. It is nonstandard and in spite of the filename
strhash.c and strhash.h, it lives in application namespace by providing
compulsory global symbols hash_create()/hash_destroy()/hash_search()/
hash_traverse()/hash_purge()/hash_stats() regardless of whether you
#include <strhash.h> or not. If it turns out that there is a huge
application for this after all, I can repocopy it somewhere safer and
we can revive it elsewhere. But please, not in libc!
package, a more recent, generalized set of routines. Among the
changes:
- Declare strtof() and strtold() in stdlib.h.
- Add glue to libc to support these routines for all kinds
of ``long double''.
- Update printf() to reflect the fact that dtoa works slightly
differently now.
As soon as I see that nothing has blown up, I will kill
src/lib/libc/stdlib/strtod.c. Soon printf() will be able
to use the new routines to output long doubles without loss
of precision, but numerous bugs in the existing code must
be addressed first.
Reviewed by: bde (briefly), mike (mentor), obrien
to Solaris, it is in /usr/libexec) to perform the handing over of tty nodes
to the user being granted the pty.
Submitted by: Ryan Younce <ryany@pobox.com>
Reviewed by: security-officer@, standards@, mike@
the compatibility library libcompat.
- Add new implementations of lsearch() and lfind() which conform to
IEEE Std 1003.1-2001 to libc. Add a new manual page for them and
add them to the makefile.
- Add function prototypes for lsearch() and lfind() to the search.h
header.
page from the compatibility library.
- Add new implementations of insque() and remque() which conform to
IEEE Std 1003.1-2001 to libc. Add a new manual page for them and
connect them to the build.
- Add the prototypes of insque() and remque() to the search.h
header.
This is a first cut, but enough to help people interested in using it
further than before.
More text coming to illustrate use and provide more details.
Based on standards' text.
my last version of this work due to HDD crash, but this version cleanly
passed all POSIX and SuSv2 tests. I am working on testing scripts which
should test this implementation against all locales and surely more fixes
will come soon.
Reviewed by: ache, silence at -audit & -developers
