[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.176 by root, Sun Jan 10 23:05:11 2010 UTC vs.
Revision 1.207 by root, Mon Jul 25 16:50:33 2011 UTC

 =head1 SYNOPSIS
  use IO::AIO;
- aio_open "/etc/passwd", O_RDONLY, 0, sub {
+ aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
     my $fh = shift
        or die "/etc/passwd: $!";
     ...
  };
    # register the IO::AIO callback with EV
    my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
    # queue the request to open /etc/passwd
-   aio_open "/etc/passwd", O_RDONLY, 0, sub {
+   aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
       my $fh = shift
          or die "error while opening: $!";
       # stat'ing filehandles is generally non-blocking
       my $size = -s $fh;
 use common::sense;
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '3.5';
+   our $VERSION = '4.0';
    our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
                      aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
-                     aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
+                     aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
-                     aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
+                     aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
+                     aio_pathsync aio_readahead
                      aio_rename aio_link aio_move aio_copy aio_group
                      aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
                      aio_chmod aio_utime aio_truncate
-                     aio_msync aio_mtouch aio_statvfs);
+                     aio_msync aio_mtouch aio_mlock aio_mlockall
+                     aio_statvfs);
    our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
    our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
-                       min_parallel max_parallel max_idle
+                       min_parallel max_parallel max_idle idle_timeout
                        nreqs nready npending nthreads
                        max_poll_time max_poll_reqs
-                       sendfile fadvise);
+                       sendfile fadvise madvise
+                       mmap munmap munlock munlockall);
    push @AIO_REQ, qw(aio_busy); # not exported
    @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
    aio_unlink $pathname, $callback->($status)
    aio_mknod $path, $mode, $dev, $callback->($status)
    aio_link $srcpath, $dstpath, $callback->($status)
    aio_symlink $srcpath, $dstpath, $callback->($status)
    aio_readlink $path, $callback->($link)
+   aio_realpath $path, $callback->($link)
    aio_rename $srcpath, $dstpath, $callback->($status)
    aio_mkdir $pathname, $mode, $callback->($status)
    aio_rmdir $pathname, $callback->($status)
    aio_readdir $pathname, $callback->($entries)
    aio_readdirx $pathname, $flags, $callback->($entries, $flags)
    aio_copy $srcpath, $dstpath, $callback->($status)
    aio_move $srcpath, $dstpath, $callback->($status)
    aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
    aio_rmtree $path, $callback->($status)
    aio_sync $callback->($status)
+   aio_syncfs $fh, $callback->($status)
    aio_fsync $fh, $callback->($status)
    aio_fdatasync $fh, $callback->($status)
    aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
    aio_pathsync $path, $callback->($status)
    aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
    aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
+   aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
+   aio_mlockall $flags, $callback->($status)
    aio_group $callback->(...)
    aio_nop $callback->()
    $prev_pri = aioreq_pri [$pri]
    aioreq_nice $pri_adjust
    IO::AIO::max_poll_reqs $nreqs
    IO::AIO::max_poll_time $seconds
    IO::AIO::min_parallel $nthreads
    IO::AIO::max_parallel $nthreads
    IO::AIO::max_idle $nthreads
+   IO::AIO::idle_timeout $seconds
    IO::AIO::max_outstanding $maxreqs
    IO::AIO::nreqs
    IO::AIO::nready
    IO::AIO::npending
    IO::AIO::sendfile $ofh, $ifh, $offset, $count
    IO::AIO::fadvise $fh, $offset, $len, $advice
-   IO::AIO::mlockall $flags
+   IO::AIO::madvise $scalar, $offset, $length, $advice
+   IO::AIO::mprotect $scalar, $offset, $length, $protect
+   IO::AIO::munlock $scalar, $offset = 0, $length = undef
    IO::AIO::munlockall
 =head2 AIO REQUEST FUNCTIONS
 All the C<aio_*> calls are more or less thin wrappers around the syscall
 by the umask in effect then the request is being executed, so better never
 change the umask.
 Example:
-   aio_open "/etc/passwd", O_RDONLY, 0, sub {
+   aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
       if ($_[0]) {
          print "open successful, fh is $_[0]\n";
          ...
       } else {
          die "open failed: $!\n";
       }
    };
+In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
+C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
+following POSIX and non-POSIX constants are available (missing ones on
+your system are, as usual, C<0>):
+C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
+C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
+C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
 =item aio_close $fh, $callback->($status)
 Asynchronously close a file and call the callback with the result
 code.
 Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
 reading at byte offset C<$in_offset>, and starts writing at the current
 file offset of C<$out_fh>. Because of that, it is not safe to issue more
 than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
-other.
+other. The same C<$in_fh> works fine though, as this function does not
+move or use the file offset of C<$in_fh>.
+Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
+are written, and there is no way to find out how many more bytes have been
+read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
+number of bytes written to C<$out_fh>. Only if the result value equals
+C<$length> one can assume that C<$length> bytes have been read.
+Unlike with other C<aio_> functions, it makes a lot of sense to use
+C<aio_sendfile> on non-blocking sockets, as long as one end (typically
+the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
+the socket I/O will be non-blocking. Note, however, that you can run
+into a trap where C<aio_sendfile> reads some data with readahead, then
+fails to write all data, and when the socket is ready the next time, the
+data in the cache is already lost, forcing C<aio_sendfile> to again hit
+the disk. Explicit C<aio_read> + C<aio_write> let's you better control
+resource usage.
-This call tries to make use of a native C<sendfile> syscall to provide
+This call tries to make use of a native C<sendfile>-like syscall to
-zero-copy operation. For this to work, C<$out_fh> should refer to a
+provide zero-copy operation. For this to work, C<$out_fh> should refer to
-socket, and C<$in_fh> should refer to an mmap'able file.
+a socket, and C<$in_fh> should refer to an mmap'able file.
 If a native sendfile cannot be found or it fails with C<ENOSYS>,
-C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
+C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
-it will be emulated, so you can call C<aio_sendfile> on any type of
+C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
-filehandle regardless of the limitations of the operating system.
+type of filehandle regardless of the limitations of the operating system.
-Please note, however, that C<aio_sendfile> can read more bytes from
+As native sendfile syscalls (as practically any non-POSIX interface hacked
-C<$in_fh> than are written, and there is no way to find out how many
+together in a hurry to improve benchmark numbers) tend to be rather buggy
-bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
+on many systems, this implementation tries to work around some known bugs
-provides the number of bytes written to C<$out_fh>. Only if the result
+in Linux and FreeBSD kernels (probably others, too), but that might fail,
-value equals C<$length> one can assume that C<$length> bytes have been
+so you really really should check the return value of C<aio_sendfile> -
-read.
+fewre bytes than expected might have been transferred.
 =item aio_readahead $fh,$offset,$length, $callback->($retval)
 C<aio_readahead> populates the page cache with data from a file so that
 for an explanation.
 Currently, the stats are always 64-bit-stats, i.e. instead of returning an
 error when stat'ing a large file, the results will be silently truncated
 unless perl itself is compiled with large file support.
+To help interpret the mode and dev/rdev stat values, IO::AIO offers the
+following constants and functions (if not implemented, the constants will
+be C<0> and the functions will either C<croak> or fall back on traditional
+behaviour).
+C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
+C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
+C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
 Example: Print the length of F</etc/passwd>:
    aio_stat "/etc/passwd", sub {
       $_[0] and die "stat failed: $!";
 The only (POSIX-) portable way of calling this function is:
    aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
+See C<aio_stat> for info about some potentially helpful extra constants
+and functions.
 =item aio_link $srcpath, $dstpath, $callback->($status)
 Asynchronously create a new link to the existing object at C<$srcpath> at
 the path C<$dstpath> and call the callback with the result code.
 Asynchronously read the symlink specified by C<$path> and pass it to
 the callback. If an error occurs, nothing or undef gets passed to the
 callback.
+=item aio_realpath $path, $callback->($path)
+Asynchronously make the path absolute and resolve any symlinks in
+C<$path>. The resulting path only consists of directories (Same as
+L<Cwd::realpath>).
+This request can be used to get the absolute path of the current working
+directory by passing it a path of F<.> (a single dot).
 =item aio_rename $srcpath, $dstpath, $callback->($status)
 Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
 rename(2) and call the callback with the result code.
 array-ref with the filenames.
 =item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
-Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
+Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
-behaviour and output format. In case of an error, C<$entries> will be
+tune behaviour and output format. In case of an error, C<$entries> will be
 C<undef>.
 The flags are a combination of the following constants, ORed together (the
 flags will also be passed to the callback, possibly modified):
 =over 4
 =item IO::AIO::READDIR_DENTS
-When this flag is off, then the callback gets an arrayref with of names
+When this flag is off, then the callback gets an arrayref consisting of
-only (as with C<aio_readdir>), otherwise it gets an arrayref with
+names only (as with C<aio_readdir>), otherwise it gets an arrayref with
 C<[$name, $type, $inode]> arrayrefs, each describing a single directory
 entry in more detail.
 C<$name> is the name of the entry.
 systems that do not deliver the inode information.
 =item IO::AIO::READDIR_DIRS_FIRST
 When this flag is set, then the names will be returned in an order where
-likely directories come first. This is useful when you need to quickly
+likely directories come first, in optimal stat order. This is useful when
-find directories, or you want to find all directories while avoiding to
+you need to quickly find directories, or you want to find all directories
-stat() each entry.
+while avoiding to stat() each entry.
 If the system returns type information in readdir, then this is used
-to find directories directly.  Otherwise, likely directories are files
+to find directories directly. Otherwise, likely directories are names
-beginning with ".", or otherwise files with no dots, of which files with
+beginning with ".", or otherwise names with no dots, of which names with
 short names are tried first.
 =item IO::AIO::READDIR_STAT_ORDER
 When this flag is set, then the names will be returned in an order
 =item IO::AIO::READDIR_FOUND_UNKNOWN
 This flag should not be set when calling C<aio_readdirx>. Instead, it
 is being set by C<aio_readdirx>, when any of the C<$type>'s found were
-C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
+C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
 C<$type>'s are known, which can be used to speed up some algorithms.
 =back
       if ($_[0] && $! == EXDEV) {
          aioreq_pri $pri;
          add $grp aio_copy $src, $dst, sub {
             $grp->result ($_[0]);
-            if (!$_[0]) {
+            unless ($_[0]) {
                aioreq_pri $pri;
                add $grp aio_unlink $src;
             }
          };
       } else {
 Then entries will be sorted into likely directories a non-initial dot
 currently) and likely non-directories (see C<aio_readdirx>). Then every
 entry plus an appended C</.> will be C<stat>'ed, likely directories first,
 in order of their inode numbers. If that succeeds, it assumes that the
 entry is a directory or a symlink to directory (which will be checked
-seperately). This is often faster than stat'ing the entry itself because
+separately). This is often faster than stat'ing the entry itself because
 filesystems might detect the type of the entry without reading the inode
 data (e.g. ext2fs filetype feature), even on systems that cannot return
 the filetype information on readdir.
 If the known number of directories (link count - 2) has been reached, the
 callback with the fdatasync result code.
 If this call isn't available because your OS lacks it or it couldn't be
 detected, it will be emulated by calling C<fsync> instead.
+=item aio_syncfs $fh, $callback->($status)
+Asynchronously call the syncfs syscall to sync the filesystem associated
+to the given filehandle and call the callback with the syncfs result
+code. If syncfs is not available, calls sync(), but returns C<-1> and sets
+errno to C<ENOSYS> nevertheless.
 =item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
 Sync the data portion of the file specified by C<$offset> and C<$length>
 to disk (but NOT the metadata), by calling the Linux-specific
 sync_file_range call. If sync_file_range is not available or it returns
 as for C<aio_msync>, above, except for flags, which must be either
 C<0> (which reads all pages and ensures they are instantiated) or
 C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
 writing an octet from it, which dirties the page).
+=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
+This is a rather advanced IO::AIO call, which works best on mmap(2)ed
+scalars.
+It reads in all the pages of the underlying storage into memory (if any)
+and locks them, so they are not getting swapped/paged out or removed.
+If C<$length> is undefined, then the scalar will be locked till the end.
+On systems that do not implement C<mlock>, this function returns C<-1>
+and sets errno to C<ENOSYS>.
+Note that the corresponding C<munlock> is synchronous and is
+documented under L<MISCELLANEOUS FUNCTIONS>.
+Example: open a file, mmap and mlock it - both will be undone when
+C<$data> gets destroyed.
+   open my $fh, "<", $path or die "$path: $!";
+   my $data;
+   IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
+   aio_mlock $data; # mlock in background
+=item aio_mlockall $flags, $callback->($status)
+Calls the C<mlockall> function with the given C<$flags> (a combination of
+C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
+On systems that do not implement C<mlockall>, this function returns C<-1>
+and sets errno to C<ENOSYS>.
+Note that the corresponding C<munlockall> is synchronous and is
+documented under L<MISCELLANEOUS FUNCTIONS>.
+Example: asynchronously lock all current and future pages into memory.
+   aio_mlockall IO::AIO::MCL_FUTURE;
 =item aio_group $callback->(...)
 This is a very special aio request: Instead of doing something, it is a
 container for other aio requests, which is useful if you want to bundle
 many requests into a single, composite, request with a definite callback
 See C<poll_cb> for an example.
 =item IO::AIO::poll_cb
-Process some outstanding events on the result pipe. You have to call this
+Process some outstanding events on the result pipe. You have to call
-regularly. Returns C<0> if all events could be processed, or C<-1> if it
+this regularly. Returns C<0> if all events could be processed (or there
-returned earlier for whatever reason. Returns immediately when no events
+were no events to process), or C<-1> if it returned earlier for whatever
-are outstanding. The amount of events processed depends on the settings of
+reason. Returns immediately when no events are outstanding. The amount of
-C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
+events processed depends on the settings of C<IO::AIO::max_poll_req> and
+C<IO::AIO::max_poll_time>.
 If not all requests were processed for whatever reason, the filehandle
 will still be ready when C<poll_cb> returns, so normally you don't have to
 do anything special to have it called later.
+Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
+ready, it can be beneficial to call this function from loops which submit
+a lot of requests, to make sure the results get processed when they become
+available and not just when the loop is finished and the event loop takes
+over again. This function returns very fast when there are no outstanding
+requests.
 Example: Install an Event watcher that automatically calls
 IO::AIO::poll_cb with high priority (more examples can be found in the
 SYNOPSIS section, at the top of this document):
 Under normal circumstances you don't need to call this function.
 =item IO::AIO::max_idle $nthreads
-Limit the number of threads (default: 4) that are allowed to idle (i.e.,
+Limit the number of threads (default: 4) that are allowed to idle
-threads that did not get a request to process within 10 seconds). That
+(i.e., threads that did not get a request to process within the idle
-means if a thread becomes idle while C<$nthreads> other threads are also
+timeout (default: 10 seconds). That means if a thread becomes idle while
-idle, it will free its resources and exit.
+C<$nthreads> other threads are also idle, it will free its resources and
+exit.
 This is useful when you allow a large number of threads (e.g. 100 or 1000)
 to allow for extremely high load situations, but want to free resources
 under normal circumstances (1000 threads can easily consume 30MB of RAM).
 The default is probably ok in most situations, especially if thread
 creation is fast. If thread creation is very slow on your system you might
 want to use larger values.
+=item IO::AIO::idle_timeout $seconds
+Sets the minimum idle timeout (default 10) after which worker threads are
+allowed to exit. SEe C<IO::AIO::max_idle>.
 =item IO::AIO::max_outstanding $maxreqs
+Sets the maximum number of outstanding requests to C<$nreqs>. If
+you do queue up more than this number of requests, the next call to
+C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
+C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
+longer exceeded.
+In other words, this setting does not enforce a queue limit, but can be
+used to make poll functions block if the limit is exceeded.
 This is a very bad function to use in interactive programs because it
 blocks, and a bad way to reduce concurrency because it is inexact: Better
 use an C<aio_group> together with a feed callback.
-Sets the maximum number of outstanding requests to C<$nreqs>. If you
+It's main use is in scripts without an event loop - when you want to stat
-do queue up more than this number of requests, the next call to the
+a lot of files, you can write somehting like this:
-C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
-function will block until the limit is no longer exceeded.
-The default value is very large, so there is no practical limit on the
+   IO::AIO::max_outstanding 32;
-number of outstanding requests.
-You can still queue as many requests as you want. Therefore,
+   for my $path (...) {
-C<max_outstanding> is mainly useful in simple scripts (with low values) or
+      aio_stat $path , ...;
-as a stop gap to shield against fatal memory overflow (with large values).
+      IO::AIO::poll_cb;
+   }
+   IO::AIO::flush;
+The call to C<poll_cb> inside the loop will normally return instantly, but
+as soon as more thna C<32> reqeusts are in-flight, it will block until
+some requests have been handled. This keeps the loop from pushing a large
+number of C<aio_stat> requests onto the queue.
+The default value for C<max_outstanding> is very large, so there is no
+practical limit on the number of outstanding requests.
 =back
 =head3 STATISTICAL INFORMATION
 Returns the number of bytes copied, or C<-1> on error.
 =item IO::AIO::fadvise $fh, $offset, $len, $advice
-Simply calls the C<posix_fadvise> function (see it's
+Simply calls the C<posix_fadvise> function (see its
 manpage for details). The following advice constants are
-avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
+available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
 C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
 C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
 On systems that do not implement C<posix_fadvise>, this function returns
 ENOSYS, otherwise the return value of C<posix_fadvise>.
+=item IO::AIO::madvise $scalar, $offset, $len, $advice
+Simply calls the C<posix_madvise> function (see its
+manpage for details). The following advice constants are
+available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
+C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
+On systems that do not implement C<posix_madvise>, this function returns
+ENOSYS, otherwise the return value of C<posix_madvise>.
+=item IO::AIO::mprotect $scalar, $offset, $len, $protect
+Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
+$scalar (see its manpage for details). The following protect
+constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
+C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
+On systems that do not implement C<mprotect>, this function returns
+ENOSYS, otherwise the return value of C<mprotect>.
 =item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
 Memory-maps a file (or anonymous memory range) and attaches it to the
 given C<$scalar>, which will act like a string scalar.
 C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
 C<IO::AIO::MAP_NONBLOCK>
 If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
+C<$offset> is the offset from the start of the file - it generally must be
+a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
+Example:
+   use Digest::MD5;
+   use IO::AIO;
+   open my $fh, "<verybigfile"
+      or die "$!";
+   IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
+      or die "verybigfile: $!";
+   my $fast_md5 = md5 $data;
 =item IO::AIO::munmap $scalar
 Removes a previous mmap and undefines the C<$scalar>.
-=item IO::AIO::mlockall $flags
+=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
-Calls the C<mlockall> function with the given C<$flags> (a combination of
+Calls the C<munlock> function, undoing the effects of a previous
-C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL__FUTURE>).
+C<aio_mlock> call (see its description for details).
-On systems that do not implement C<mlockall>, this function returns
-ENOSYS, otherwise the return value of C<mlockall>.
 =item IO::AIO::munlockall
 Calls the C<munlockall> function.
  Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
                              \&IO::AIO::poll_cb);
 =head2 FORK BEHAVIOUR
-This module should do "the right thing" when the process using it forks:
+Usage of pthreads in a program changes the semantics of fork
+considerably. Specifically, only async-safe functions can be called after
+fork. Perl doesn't know about this, so in general, you cannot call fork
+with defined behaviour in perl if pthreads are involved. IO::AIO uses
+pthreads, so this applies, but many other extensions and (for inexplicable
+reasons) perl itself often is linked against pthreads, so this limitation
+applies to quite a lot of perls.
-Before the fork, IO::AIO enters a quiescent state where no requests
+This module no longer tries to fight your OS, or POSIX. That means IO::AIO
-can be added in other threads and no results will be processed. After
+only works in the process that loaded it. Forking is fully supported, but
-the fork the parent simply leaves the quiescent state and continues
+using IO::AIO in the child is not.
-request/result processing, while the child frees the request/result queue
-(so that the requests started before the fork will only be handled in the
-parent). Threads will be started on demand until the limit set in the
-parent process has been reached again.
-In short: the parent will, after a short pause, continue as if fork had
+You might get around by not I<using> IO::AIO before (or after)
-not been called, while the child will act as if IO::AIO has not been used
+forking. You could also try to call the L<IO::AIO::reinit> function in the
-yet.
+child:
+=over 4
+=item IO::AIO::reinit
+Abandons all current requests and I/O threads and simply reinitialises all
+data structures. This is not an operation supported by any standards, but
+happens to work on GNU/Linux and some newer BSD systems.
+The only reasonable use for this function is to call it after forking, if
+C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
+the process will result in undefined behaviour. Calling it at any time
+will also result in any undefined (by POSIX) behaviour.
+=back
 =head2 MEMORY USAGE
 Per-request usage:

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.176 by root, Sun Jan 10 23:05:11 2010 UTC vs. Revision 1.207 by root, Mon Jul 25 16:50:33 2011 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.176 by root, Sun Jan 10 23:05:11 2010 UTC vs.
Revision 1.207 by root, Mon Jul 25 16:50:33 2011 UTC