--- IO-AIO/README 2007/10/06 14:05:37 1.27 +++ IO-AIO/README 2008/10/02 11:35:03 1.32 @@ -26,9 +26,11 @@ my $grp = aio_group sub { print "all stats done\n" }; add $grp aio_stat "..." for ...; - # AnyEvent integration - open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; - my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); + # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...) + use AnyEvent::AIO; + + # EV integration + my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; # Event integration Event->io (fd => IO::AIO::poll_fileno, @@ -175,8 +177,8 @@ identical, and they all accept an additional (and optional) $callback argument which must be a code reference. This code reference will get called with the syscall return code (e.g. most syscalls return -1 on - error, unlike perl, which usually delivers "false") as it's sole - argument when the given syscall has been executed asynchronously. + error, unlike perl, which usually delivers "false") as its sole argument + after the given syscall has been executed asynchronously. All functions expecting a filehandle keep a copy of the filehandle internally until the request has finished. @@ -199,7 +201,7 @@ contents. This works, btw. independent of the internal UTF-8 bit, which IO::AIO - handles correctly wether it is set or not. + handles correctly whether it is set or not. $prev_pri = aioreq_pri [$pri] Returns the priority value that would be used for the next request @@ -264,34 +266,14 @@ Unfortunately, you can't do this to perl. Perl *insists* very strongly on closing the file descriptor associated with the - filehandle itself. Here is what aio_close will try: - - 1. dup()licate the fd - 2. asynchronously close() the duplicated fd - 3. dup()licate the fd once more - 4. let perl close() the filehandle - 5. asynchronously close the duplicated fd - - The idea is that the first close() flushes stuff to disk that - closing an fd will flush, so when perl closes the fd, nothing much - will need to be flushed. The second async. close() will then flush - stuff to disk that closing the last fd to the file will flush. - - Just FYI, SuSv3 has this to say on close: - - All outstanding record locks owned by the process on the file - associated with the file descriptor shall be removed. - - If fildes refers to a socket, close() shall cause the socket to be - destroyed. ... close() shall block for up to the current linger - interval until all data is transmitted. - [this actually sounds like a specification bug, but who knows] + filehandle itself. - And at least Linux additionally actually flushes stuff on every - close, even when the file itself is still open. + Therefore, "aio_close" will not close the filehandle - instead it + will use dup2 to overwrite the file descriptor with the write-end of + a pipe (the pipe fd will be created on demand and will be cached). - Sounds enourmously inefficient and complicated? Yes... please show - me how to nuke perl's fd out of existence... + Or in other words: the file descriptor will be closed, but it will + not be free for reuse until the perl filehandle is closed. aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) @@ -471,10 +453,10 @@ or destination) from $srcpath to $dstpath and call the callback with the 0 (error) or -1 ok. - This is a composite request that it creates the destination file - with mode 0200 and copies the contents of the source file into it - using "aio_sendfile", followed by restoring atime, mtime, access - mode and uid/gid, in that order. + This is a composite request that creates the destination file with + mode 0200 and copies the contents of the source file into it using + "aio_sendfile", followed by restoring atime, mtime, access mode and + uid/gid, in that order. If an error occurs, the partial destination file will be unlinked, if possible, except when setting atime, mtime, access mode and @@ -548,6 +530,9 @@ uses "aio_scandir" to recurse into and rmdir directories, and unlink everything else. + aio_sync $callback->($status) + Asynchronously call sync and call the callback when finished. + aio_fsync $fh, $callback->($status) Asynchronously call fsync on the given filehandle and call the callback with the fsync result code. @@ -559,6 +544,16 @@ If this call isn't available because your OS lacks it or it couldn't be detected, it will be emulated by calling "fsync" instead. + aio_pathsync $path, $callback->($status) + This request tries to open, fsync and close the given path. This is + a composite request intended to sync directories after directory + operations (E.g. rename). This might not work on all operating + systems or have any specific effect, but usually it makes sure that + directory changes get written to disc. It works for anything that + can be opened for read-only, not just directories. + + Passes 0 when everything went ok, and -1 on error. + 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 @@ -649,23 +644,27 @@ This makes it very easy to create composite requests (see the source of "aio_move" for an application) that work and feel like simple requests. - * The IO::AIO::GRP objects will be cleaned up during calls to - "IO::AIO::poll_cb", just like any other request. - * They can be canceled like any other request. Canceling will cancel not - only the request itself, but also all requests it contains. - * They can also can also be added to other IO::AIO::GRP objects. - * You must not add requests to a group from within the group callback - (or any later time). + * The IO::AIO::GRP objects will be cleaned up during calls to + "IO::AIO::poll_cb", just like any other request. + + * They can be canceled like any other request. Canceling will cancel + not only the request itself, but also all requests it contains. + + * They can also can also be added to other IO::AIO::GRP objects. + + * You must not add requests to a group from within the group callback + (or any later time). Their lifetime, simplified, looks like this: when they are empty, they will finish very quickly. If they contain only requests that are in the "done" state, they will also finish. Otherwise they will continue to exist. - That means after creating a group you have some time to add requests. - And in the callbacks of those requests, you can add further requests to - the group. And only when all those requests have finished will the the - group itself finish. + That means after creating a group you have some time to add requests + (precisely before the callback has been invoked, which is only done + within the "poll_cb"). And in the callbacks of those requests, you can + add further requests to the group. And only when all those requests have + finished will the the group itself finish. add $grp ... $grp->add (...) @@ -682,7 +681,7 @@ $grp->result (...) Set the result value(s) that will be passed to the group callback - when all subrequests have finished and set thre groups errno to the + when all subrequests have finished and set the groups errno to the current value of errno (just like calling "errno" without an error number). By default, no argument will be passed and errno is zero. @@ -751,13 +750,15 @@ IO::AIO::poll_cb Process some outstanding events on the result pipe. You have to call - this regularly. Returns the number of events processed. Returns - immediately when no events are outstanding. The amount of events - processed depends on the settings of "IO::AIO::max_poll_req" and + this regularly. Returns 0 if all events could be processed, or -1 if + it returned earlier for whatever reason. Returns immediately when no + events are outstanding. The amount of events processed depends on + the settings of "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". If not all requests were processed for whatever reason, the - filehandle will still be ready when "poll_cb" returns. + filehandle will still be ready when "poll_cb" returns, so normally + you don't have to do anything special to have it called later. Example: Install an Event watcher that automatically calls IO::AIO::poll_cb with high priority: @@ -873,7 +874,7 @@ creation is fast. If thread creation is very slow on your system you might want to use larger values. - $oldmaxreqs = IO::AIO::max_outstanding $maxreqs + IO::AIO::max_outstanding $maxreqs 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 "aio_group" together with a feed callback. @@ -887,7 +888,7 @@ the number of outstanding requests. You can still queue as many requests as you want. Therefore, - "max_oustsanding" is mainly useful in simple scripts (with low + "max_outstanding" is mainly useful in simple scripts (with low values) or as a stop gap to shield against fatal memory overflow (with large values). @@ -947,7 +948,8 @@ Known bugs will be fixed in the next release. SEE ALSO - Coro::AIO. + AnyEvent::AIO for easy integration into event loops, Coro::AIO for a + more natural syntax. AUTHOR Marc Lehmann