contrib/jemalloc/INSTALL.md

Building and installing a packaged release of jemalloc can be as simple as
typing the following while in the root directory of the source tree:

    ./configure
    make
    make install

If building from unpackaged developer sources, the simplest command sequence
that might work is:

    ./autogen.sh
    make
    make install

You can uninstall the installed build artifacts like this:

    make uninstall

Notes:
 - "autoconf" needs to be installed
 - Documentation is built by the default target only when xsltproc is
available.  Build will warn but not stop if the dependency is missing.


## Advanced configuration

The 'configure' script supports numerous options that allow control of which
functionality is enabled, where jemalloc is installed, etc.  Optionally, pass
any of the following arguments (not a definitive list) to 'configure':

* `--help`

    Print a definitive list of options.

* `--prefix=<install-root-dir>`

    Set the base directory in which to install.  For example:

        ./configure --prefix=/usr/local

    will cause files to be installed into /usr/local/include, /usr/local/lib,
    and /usr/local/man.

* `--with-version=(<major>.<minor>.<bugfix>-<nrev>-g<gid>|VERSION)`

    The VERSION file is mandatory for successful configuration, and the
    following steps are taken to assure its presence:
    1) If --with-version=<major>.<minor>.<bugfix>-<nrev>-g<gid> is specified,
       generate VERSION using the specified value.
    2) If --with-version is not specified in either form and the source
       directory is inside a git repository, try to generate VERSION via 'git
       describe' invocations that pattern-match release tags.
    3) If VERSION is missing, generate it with a bogus version:
       0.0.0-0-g0000000000000000000000000000000000000000

    Note that --with-version=VERSION bypasses (1) and (2), which simplifies
    VERSION configuration when embedding a jemalloc release into another
    project's git repository.

* `--with-rpath=<colon-separated-rpath>`

    Embed one or more library paths, so that libjemalloc can find the libraries
    it is linked to.  This works only on ELF-based systems.

* `--with-mangling=<map>`

    Mangle public symbols specified in <map> which is a comma-separated list of
    name:mangled pairs.

    For example, to use ld's --wrap option as an alternative method for
    overriding libc's malloc implementation, specify something like:

      --with-mangling=malloc:__wrap_malloc,free:__wrap_free[...]

    Note that mangling happens prior to application of the prefix specified by
    --with-jemalloc-prefix, and mangled symbols are then ignored when applying
    the prefix.

* `--with-jemalloc-prefix=<prefix>`

    Prefix all public APIs with <prefix>.  For example, if <prefix> is
    "prefix_", API changes like the following occur:

      malloc()         --> prefix_malloc()
      malloc_conf      --> prefix_malloc_conf
      /etc/malloc.conf --> /etc/prefix_malloc.conf
      MALLOC_CONF      --> PREFIX_MALLOC_CONF

    This makes it possible to use jemalloc at the same time as the system
    allocator, or even to use multiple copies of jemalloc simultaneously.

    By default, the prefix is "", except on OS X, where it is "je_".  On OS X,
    jemalloc overlays the default malloc zone, but makes no attempt to actually
    replace the "malloc", "calloc", etc. symbols.

* `--without-export`

    Don't export public APIs.  This can be useful when building jemalloc as a
    static library, or to avoid exporting public APIs when using the zone
    allocator on OSX.

* `--with-private-namespace=<prefix>`

    Prefix all library-private APIs with <prefix>je_.  For shared libraries,
    symbol visibility mechanisms prevent these symbols from being exported, but
    for static libraries, naming collisions are a real possibility.  By
    default, <prefix> is empty, which results in a symbol prefix of je_ .

* `--with-install-suffix=<suffix>`

    Append <suffix> to the base name of all installed files, such that multiple
    versions of jemalloc can coexist in the same installation directory.  For
    example, libjemalloc.so.0 becomes libjemalloc<suffix>.so.0.

* `--with-malloc-conf=<malloc_conf>`

    Embed `<malloc_conf>` as a run-time options string that is processed prior to
    the malloc_conf global variable, the /etc/malloc.conf symlink, and the
    MALLOC_CONF environment variable.  For example, to change the default decay
    time to 30 seconds:

      --with-malloc-conf=decay_ms:30000

* `--enable-debug`

    Enable assertions and validation code.  This incurs a substantial
    performance hit, but is very useful during application development.

* `--disable-stats`

    Disable statistics gathering functionality.  See the "opt.stats_print"
    option documentation for usage details.

* `--enable-prof`

    Enable heap profiling and leak detection functionality.  See the "opt.prof"
    option documentation for usage details.  When enabled, there are several
    approaches to backtracing, and the configure script chooses the first one
    in the following list that appears to function correctly:

    + libunwind      (requires --enable-prof-libunwind)
    + libgcc         (unless --disable-prof-libgcc)
    + gcc intrinsics (unless --disable-prof-gcc)

* `--enable-prof-libunwind`

    Use the libunwind library (http://www.nongnu.org/libunwind/) for stack
    backtracing.

* `--disable-prof-libgcc`

    Disable the use of libgcc's backtracing functionality.

* `--disable-prof-gcc`

    Disable the use of gcc intrinsics for backtracing.

* `--with-static-libunwind=<libunwind.a>`

    Statically link against the specified libunwind.a rather than dynamically
    linking with -lunwind.

* `--disable-fill`

    Disable support for junk/zero filling of memory.  See the "opt.junk" and
    "opt.zero" option documentation for usage details.

* `--disable-zone-allocator`

    Disable zone allocator for Darwin.  This means jemalloc won't be hooked as
    the default allocator on OSX/iOS.

* `--enable-utrace`

    Enable utrace(2)-based allocation tracing.  This feature is not broadly
    portable (FreeBSD has it, but Linux and OS X do not).

* `--enable-xmalloc`

    Enable support for optional immediate termination due to out-of-memory
    errors, as is commonly implemented by "xmalloc" wrapper function for malloc.
    See the "opt.xmalloc" option documentation for usage details.

* `--enable-lazy-lock`

    Enable code that wraps pthread_create() to detect when an application
    switches from single-threaded to multi-threaded mode, so that it can avoid
    mutex locking/unlocking operations while in single-threaded mode.  In
    practice, this feature usually has little impact on performance unless
    thread-specific caching is disabled.

* `--disable-cache-oblivious`

    Disable cache-oblivious large allocation alignment by default, for large
    allocation requests with no alignment constraints.  If this feature is
    disabled, all large allocations are page-aligned as an implementation
    artifact, which can severely harm CPU cache utilization.  However, the
    cache-oblivious layout comes at the cost of one extra page per large
    allocation, which in the most extreme case increases physical memory usage
    for the 16 KiB size class to 20 KiB.

* `--disable-syscall`

    Disable use of syscall(2) rather than {open,read,write,close}(2).  This is
    intended as a workaround for systems that place security limitations on
    syscall(2).

* `--disable-cxx`

    Disable C++ integration.  This will cause new and delete operator
    implementations to be omitted.

* `--with-xslroot=<path>`

    Specify where to find DocBook XSL stylesheets when building the
    documentation.

* `--with-lg-page=<lg-page>`

    Specify the base 2 log of the allocator page size, which must in turn be at
    least as large as the system page size.  By default the configure script
    determines the host's page size and sets the allocator page size equal to
    the system page size, so this option need not be specified unless the
    system page size may change between configuration and execution, e.g. when
    cross compiling.

* `--with-lg-hugepage=<lg-hugepage>`

    Specify the base 2 log of the system huge page size.  This option is useful
    when cross compiling, or when overriding the default for systems that do
    not explicitly support huge pages.

* `--with-lg-quantum=<lg-quantum>`

    Specify the base 2 log of the minimum allocation alignment.  jemalloc needs
    to know the minimum alignment that meets the following C standard
    requirement (quoted from the April 12, 2011 draft of the C11 standard):

    >  The pointer returned if the allocation succeeds is suitably aligned so
      that it may be assigned to a pointer to any type of object with a
      fundamental alignment requirement and then used to access such an object
      or an array of such objects in the space allocated [...]

    This setting is architecture-specific, and although jemalloc includes known
    safe values for the most commonly used modern architectures, there is a
    wrinkle related to GNU libc (glibc) that may impact your choice of
    <lg-quantum>.  On most modern architectures, this mandates 16-byte
    alignment (<lg-quantum>=4), but the glibc developers chose not to meet this
    requirement for performance reasons.  An old discussion can be found at
    <https://sourceware.org/bugzilla/show_bug.cgi?id=206> .  Unlike glibc,
    jemalloc does follow the C standard by default (caveat: jemalloc
    technically cheats for size classes smaller than the quantum), but the fact
    that Linux systems already work around this allocator noncompliance means
    that it is generally safe in practice to let jemalloc's minimum alignment
    follow glibc's lead.  If you specify `--with-lg-quantum=3` during
    configuration, jemalloc will provide additional size classes that are not
    16-byte-aligned (24, 40, and 56).

* `--with-lg-vaddr=<lg-vaddr>`

    Specify the number of significant virtual address bits.  By default, the
    configure script attempts to detect virtual address size on those platforms
    where it knows how, and picks a default otherwise.  This option may be
    useful when cross-compiling.

* `--disable-initial-exec-tls`

    Disable the initial-exec TLS model for jemalloc's internal thread-local
    storage (on those platforms that support explicit settings).  This can allow
    jemalloc to be dynamically loaded after program startup (e.g. using dlopen).
    Note that in this case, there will be two malloc implementations operating
    in the same process, which will almost certainly result in confusing runtime
    crashes if pointers leak from one implementation to the other.

* `--disable-libdl`

    Disable the usage of libdl, namely dlsym(3) which is required by the lazy
    lock option.  This can allow building static binaries.

The following environment variables (not a definitive list) impact configure's
behavior:

* `CFLAGS="?"`
* `CXXFLAGS="?"`

    Pass these flags to the C/C++ compiler.  Any flags set by the configure
    script are prepended, which means explicitly set flags generally take
    precedence.  Take care when specifying flags such as -Werror, because
    configure tests may be affected in undesirable ways.

* `EXTRA_CFLAGS="?"`
* `EXTRA_CXXFLAGS="?"`

    Append these flags to CFLAGS/CXXFLAGS, without passing them to the
    compiler(s) during configuration.  This makes it possible to add flags such
    as -Werror, while allowing the configure script to determine what other
    flags are appropriate for the specified configuration.

* `CPPFLAGS="?"`

    Pass these flags to the C preprocessor.  Note that CFLAGS is not passed to
    'cpp' when 'configure' is looking for include files, so you must use
    CPPFLAGS instead if you need to help 'configure' find header files.

* `LD_LIBRARY_PATH="?"`

    'ld' uses this colon-separated list to find libraries.

* `LDFLAGS="?"`

    Pass these flags when linking.

* `PATH="?"`

    'configure' uses this to find programs.

In some cases it may be necessary to work around configuration results that do
not match reality.  For example, Linux 4.5 added support for the MADV_FREE flag
to madvise(2), which can cause problems if building on a host with MADV_FREE
support and deploying to a target without.  To work around this, use a cache
file to override the relevant configuration variable defined in configure.ac,
e.g.:

    echo "je_cv_madv_free=no" > config.cache && ./configure -C


## Advanced compilation

To build only parts of jemalloc, use the following targets:

    build_lib_shared
    build_lib_static
    build_lib
    build_doc_html
    build_doc_man
    build_doc

To install only parts of jemalloc, use the following targets:

    install_bin
    install_include
    install_lib_shared
    install_lib_static
    install_lib_pc
    install_lib
    install_doc_html
    install_doc_man
    install_doc

To clean up build results to varying degrees, use the following make targets:

    clean
    distclean
    relclean


## Advanced installation

Optionally, define make variables when invoking make, including (not
exclusively):

* `INCLUDEDIR="?"`

    Use this as the installation prefix for header files.

* `LIBDIR="?"`

    Use this as the installation prefix for libraries.

* `MANDIR="?"`

    Use this as the installation prefix for man pages.

* `DESTDIR="?"`

    Prepend DESTDIR to INCLUDEDIR, LIBDIR, DATADIR, and MANDIR.  This is useful
    when installing to a different path than was specified via --prefix.

* `CC="?"`

    Use this to invoke the C compiler.

* `CFLAGS="?"`

    Pass these flags to the compiler.

* `CPPFLAGS="?"`

    Pass these flags to the C preprocessor.

* `LDFLAGS="?"`

    Pass these flags when linking.

* `PATH="?"`

    Use this to search for programs used during configuration and building.


## Development

If you intend to make non-trivial changes to jemalloc, use the 'autogen.sh'
script rather than 'configure'.  This re-generates 'configure', enables
configuration dependency rules, and enables re-generation of automatically
generated source files.

The build system supports using an object directory separate from the source
tree.  For example, you can create an 'obj' directory, and from within that
directory, issue configuration and build commands:

    autoconf
    mkdir obj
    cd obj
    ../configure --enable-autogen
    make


## Documentation

The manual page is generated in both html and roff formats.  Any web browser
can be used to view the html manual.  The roff manual page can be formatted
prior to installation via the following command:

    nroff -man -t doc/jemalloc.3