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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.194 by root, Fri May 27 00:44:49 2011 UTC vs.
Revision 1.208 by root, Mon Sep 26 20:19:08 2011 UTC

 use common::sense;
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '3.9';
+   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_mlock aio_mlockall
-                     aio_statvfs);
+                     aio_statvfs
+                     aio_wd);
    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 idle_timeout
                        nreqs nready npending nthreads
 This section simply lists the prototypes of the most important functions
 for quick reference. See the following sections for function-by-function
 documentation.
+   aio_wd $pathname, $callback->($wd)
    aio_open $pathname, $flags, $mode, $callback->($fh)
    aio_close $fh, $callback->($status)
    aio_read  $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
    aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
    aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
    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)
 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<$in_fh> than
-are written, and there is no way to find out how many bytes have been read
+are written, and there is no way to find out how many more bytes have been
-from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of
+read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
-bytes written to C<$out_fh>. Only if the result value equals C<$length>
+number of bytes written to C<$out_fh>. Only if the result value equals
-one can assume that C<$length> bytes have been read.
+C<$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
+the socket I/O will be non-blocking. Note, however, that you can run
-a trap where C<aio_sendfile> reads some data with readahead, then fails
+into a trap where C<aio_sendfile> reads some data with readahead, then
-to write all data, and when the socket is ready the next time, the data
+fails to write all data, and when the socket is ready the next time, the
-in the cache is already lost, forcing C<aio_sendfile> to again hit the
+data in the cache is already lost, forcing C<aio_sendfile> to again hit
-disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage
+the disk. Explicit C<aio_read> + C<aio_write> let's you better control
-much better.
+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.
+As native sendfile syscalls (as practically any non-POSIX interface hacked
+together in a hurry to improve benchmark numbers) tend to be rather buggy
+on many systems, this implementation tries to work around some known bugs
+in Linux and FreeBSD kernels (probably others, too), but that might fail,
+so you really really should check the return value of C<aio_sendfile> -
+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
 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<$entries> will be
 C<undef>.
 The flags are a combination of the following constants, ORed together (the
 flags will also be passed to the callback, possibly modified):
 =item IO::AIO::READDIR_FOUND_UNKNOWN
 This flag should not be set when calling C<aio_readdirx>. Instead, it
 is being set by C<aio_readdirx>, when any of the C<$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
 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
 =item IO::AIO::fadvise $fh, $offset, $len, $advice
 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
-avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
+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 avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
+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>.
  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 1.194 by root, Fri May 27 00:44:49 2011 UTC vs. Revision 1.208 by root, Mon Sep 26 20:19:08 2011 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.194 by root, Fri May 27 00:44:49 2011 UTC vs.
Revision 1.208 by root, Mon Sep 26 20:19:08 2011 UTC