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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.184 by root, Mon Nov 1 22:03:43 2010 UTC vs.
Revision 1.199 by root, Wed Jun 29 12:46:36 2011 UTC

 use common::sense;
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '3.7';
+   our $VERSION = '3.92';
    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_fdatasync aio_sync_file_range aio_pathsync aio_readahead
                      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 madvise
                        mmap munmap munlock munlockall);
    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
       } 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.
 =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
       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 {
 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
  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. 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.
-Before the fork, IO::AIO enters a quiescent state where no requests
+Some operating systems have extensions that allow safe use of fork, and
-can be added in other threads and no results will be processed. After
+this module should do "the right thing" on those, and tries on others. At
-the fork the parent simply leaves the quiescent state and continues
+the time of this writing (2011) only GNU/Linux supports these extensions
-request/result processing, while the child frees the request/result queue
+to POSIX.
-(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
-not been called, while the child will act as if IO::AIO has not been used
-yet.
 =head2 MEMORY USAGE
 Per-request usage:

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.184 by root, Mon Nov 1 22:03:43 2010 UTC vs. Revision 1.199 by root, Wed Jun 29 12:46:36 2011 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.184 by root, Mon Nov 1 22:03:43 2010 UTC vs.
Revision 1.199 by root, Wed Jun 29 12:46:36 2011 UTC