… | |
… | |
298 | If you don't know what event loop to use, use the one returned from this |
298 | If you don't know what event loop to use, use the one returned from this |
299 | function. |
299 | function. |
300 | |
300 | |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
303 | as loops cannot bes hared easily between threads anyway). |
303 | as loops cannot be shared easily between threads anyway). |
304 | |
304 | |
305 | The default loop is the only loop that can handle C<ev_signal> and |
305 | The default loop is the only loop that can handle C<ev_signal> and |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
386 | For few fds, this backend is a bit little slower than poll and select, |
386 | For few fds, this backend is a bit little slower than poll and select, |
387 | but it scales phenomenally better. While poll and select usually scale |
387 | but it scales phenomenally better. While poll and select usually scale |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
389 | epoll scales either O(1) or O(active_fds). |
389 | epoll scales either O(1) or O(active_fds). |
390 | |
390 | |
391 | The epoll syscalls are the most misdesigned of the more advanced |
391 | The epoll syscalls are the most misdesigned of the more advanced event |
392 | event mechanisms: probelsm include silently dropping events in some |
392 | mechanisms: problems include silently dropping fds, requiring a system |
393 | hard-to-detect cases, requiring a system call per fd change, no fork |
393 | call per change per fd (and unnecessary guessing of parameters), problems |
394 | support, problems with dup and so on. |
394 | with dup and so on. The biggest issue is fork races, however - if a |
|
|
395 | program forks then I<both> parent and child process have to recreate the |
|
|
396 | epoll set, which can take considerable time (one syscall per fd) and is of |
|
|
397 | course hard to detect. |
395 | |
398 | |
396 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
399 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
397 | of course doesn't, and epoll just loves to report events for totally |
400 | of course doesn't, and epoll just loves to report events for totally |
398 | I<different> file descriptors (even already closed ones, so one cannot |
401 | I<different> file descriptors (even already closed ones, so one cannot |
399 | even remove them from the set) than registered in the set (especially |
402 | even remove them from the set) than registered in the set (especially |
… | |
… | |
409 | |
412 | |
410 | Best performance from this backend is achieved by not unregistering all |
413 | Best performance from this backend is achieved by not unregistering all |
411 | watchers for a file descriptor until it has been closed, if possible, |
414 | watchers for a file descriptor until it has been closed, if possible, |
412 | i.e. keep at least one watcher active per fd at all times. Stopping and |
415 | i.e. keep at least one watcher active per fd at all times. Stopping and |
413 | starting a watcher (without re-setting it) also usually doesn't cause |
416 | starting a watcher (without re-setting it) also usually doesn't cause |
414 | extra overhead. |
417 | extra overhead. A fork can both result in spurious notifications as well |
|
|
418 | as in libev having to destroy and recreate the epoll object, which can |
|
|
419 | take considerable time and thus should be avoided. |
415 | |
420 | |
416 | While nominally embeddable in other event loops, this feature is broken in |
421 | While nominally embeddable in other event loops, this feature is broken in |
417 | all kernel versions tested so far. |
422 | all kernel versions tested so far. |
418 | |
423 | |
419 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
424 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
434 | |
439 | |
435 | It scales in the same way as the epoll backend, but the interface to the |
440 | It scales in the same way as the epoll backend, but the interface to the |
436 | kernel is more efficient (which says nothing about its actual speed, of |
441 | kernel is more efficient (which says nothing about its actual speed, of |
437 | course). While stopping, setting and starting an I/O watcher does never |
442 | course). While stopping, setting and starting an I/O watcher does never |
438 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
443 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
439 | two event changes per incident. Support for C<fork ()> is very bad and it |
444 | two event changes per incident. Support for C<fork ()> is very bad (but |
440 | drops fds silently in similarly hard-to-detect cases. |
445 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
446 | cases |
441 | |
447 | |
442 | This backend usually performs well under most conditions. |
448 | This backend usually performs well under most conditions. |
443 | |
449 | |
444 | While nominally embeddable in other event loops, this doesn't work |
450 | While nominally embeddable in other event loops, this doesn't work |
445 | everywhere, so you might need to test for this. And since it is broken |
451 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
474 | might perform better. |
480 | might perform better. |
475 | |
481 | |
476 | On the positive side, with the exception of the spurious readiness |
482 | On the positive side, with the exception of the spurious readiness |
477 | notifications, this backend actually performed fully to specification |
483 | notifications, this backend actually performed fully to specification |
478 | in all tests and is fully embeddable, which is a rare feat among the |
484 | in all tests and is fully embeddable, which is a rare feat among the |
479 | OS-specific backends. |
485 | OS-specific backends (I vastly prefer correctness over speed hacks). |
480 | |
486 | |
481 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
487 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
482 | C<EVBACKEND_POLL>. |
488 | C<EVBACKEND_POLL>. |
483 | |
489 | |
484 | =item C<EVBACKEND_ALL> |
490 | =item C<EVBACKEND_ALL> |
… | |
… | |
641 | the loop. |
647 | the loop. |
642 | |
648 | |
643 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
649 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
644 | necessary) and will handle those and any already outstanding ones. It |
650 | necessary) and will handle those and any already outstanding ones. It |
645 | will block your process until at least one new event arrives (which could |
651 | will block your process until at least one new event arrives (which could |
646 | be an event internal to libev itself, so there is no guarentee that a |
652 | be an event internal to libev itself, so there is no guarantee that a |
647 | user-registered callback will be called), and will return after one |
653 | user-registered callback will be called), and will return after one |
648 | iteration of the loop. |
654 | iteration of the loop. |
649 | |
655 | |
650 | This is useful if you are waiting for some external event in conjunction |
656 | This is useful if you are waiting for some external event in conjunction |
651 | with something not expressible using other libev watchers (i.e. "roll your |
657 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
1916 | |
1922 | |
1917 | |
1923 | |
1918 | =head2 C<ev_stat> - did the file attributes just change? |
1924 | =head2 C<ev_stat> - did the file attributes just change? |
1919 | |
1925 | |
1920 | This watches a file system path for attribute changes. That is, it calls |
1926 | This watches a file system path for attribute changes. That is, it calls |
1921 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1927 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1922 | compared to the last time, invoking the callback if it did. |
1928 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1929 | it did. |
1923 | |
1930 | |
1924 | The path does not need to exist: changing from "path exists" to "path does |
1931 | The path does not need to exist: changing from "path exists" to "path does |
1925 | not exist" is a status change like any other. The condition "path does |
1932 | not exist" is a status change like any other. The condition "path does |
1926 | not exist" is signified by the C<st_nlink> field being zero (which is |
1933 | not exist" is signified by the C<st_nlink> field being zero (which is |
1927 | otherwise always forced to be at least one) and all the other fields of |
1934 | otherwise always forced to be at least one) and all the other fields of |
1928 | the stat buffer having unspecified contents. |
1935 | the stat buffer having unspecified contents. |
1929 | |
1936 | |
1930 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1937 | The path I<must not> end in a slash or contain special components such as |
|
|
1938 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1931 | relative and your working directory changes, the behaviour is undefined. |
1939 | your working directory changes, then the behaviour is undefined. |
1932 | |
1940 | |
1933 | Since there is no standard kernel interface to do this, the portable |
1941 | Since there is no portable change notification interface available, the |
1934 | implementation simply calls C<stat (2)> regularly on the path to see if |
1942 | portable implementation simply calls C<stat(2)> regularly on the path |
1935 | it changed somehow. You can specify a recommended polling interval for |
1943 | to see if it changed somehow. You can specify a recommended polling |
1936 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1944 | interval for this case. If you specify a polling interval of C<0> (highly |
1937 | then a I<suitable, unspecified default> value will be used (which |
1945 | recommended!) then a I<suitable, unspecified default> value will be used |
1938 | you can expect to be around five seconds, although this might change |
1946 | (which you can expect to be around five seconds, although this might |
1939 | dynamically). Libev will also impose a minimum interval which is currently |
1947 | change dynamically). Libev will also impose a minimum interval which is |
1940 | around C<0.1>, but thats usually overkill. |
1948 | currently around C<0.1>, but that's usually overkill. |
1941 | |
1949 | |
1942 | This watcher type is not meant for massive numbers of stat watchers, |
1950 | This watcher type is not meant for massive numbers of stat watchers, |
1943 | as even with OS-supported change notifications, this can be |
1951 | as even with OS-supported change notifications, this can be |
1944 | resource-intensive. |
1952 | resource-intensive. |
1945 | |
1953 | |
… | |
… | |
1955 | support disabled by default, you get the 32 bit version of the stat |
1963 | support disabled by default, you get the 32 bit version of the stat |
1956 | structure. When using the library from programs that change the ABI to |
1964 | structure. When using the library from programs that change the ABI to |
1957 | use 64 bit file offsets the programs will fail. In that case you have to |
1965 | use 64 bit file offsets the programs will fail. In that case you have to |
1958 | compile libev with the same flags to get binary compatibility. This is |
1966 | compile libev with the same flags to get binary compatibility. This is |
1959 | obviously the case with any flags that change the ABI, but the problem is |
1967 | obviously the case with any flags that change the ABI, but the problem is |
1960 | most noticeably disabled with ev_stat and large file support. |
1968 | most noticeably displayed with ev_stat and large file support. |
1961 | |
1969 | |
1962 | The solution for this is to lobby your distribution maker to make large |
1970 | The solution for this is to lobby your distribution maker to make large |
1963 | file interfaces available by default (as e.g. FreeBSD does) and not |
1971 | file interfaces available by default (as e.g. FreeBSD does) and not |
1964 | optional. Libev cannot simply switch on large file support because it has |
1972 | optional. Libev cannot simply switch on large file support because it has |
1965 | to exchange stat structures with application programs compiled using the |
1973 | to exchange stat structures with application programs compiled using the |
… | |
… | |
1984 | descriptor open on the object at all times, and detecting renames, unlinks |
1992 | descriptor open on the object at all times, and detecting renames, unlinks |
1985 | etc. is difficult. |
1993 | etc. is difficult. |
1986 | |
1994 | |
1987 | =head3 The special problem of stat time resolution |
1995 | =head3 The special problem of stat time resolution |
1988 | |
1996 | |
1989 | The C<stat ()> system call only supports full-second resolution portably, and |
1997 | The C<stat ()> system call only supports full-second resolution portably, |
1990 | even on systems where the resolution is higher, most file systems still |
1998 | and even on systems where the resolution is higher, most file systems |
1991 | only support whole seconds. |
1999 | still only support whole seconds. |
1992 | |
2000 | |
1993 | That means that, if the time is the only thing that changes, you can |
2001 | That means that, if the time is the only thing that changes, you can |
1994 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2002 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1995 | calls your callback, which does something. When there is another update |
2003 | calls your callback, which does something. When there is another update |
1996 | within the same second, C<ev_stat> will be unable to detect unless the |
2004 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2635 | =over 4 |
2643 | =over 4 |
2636 | |
2644 | |
2637 | =item ev_async_init (ev_async *, callback) |
2645 | =item ev_async_init (ev_async *, callback) |
2638 | |
2646 | |
2639 | Initialises and configures the async watcher - it has no parameters of any |
2647 | Initialises and configures the async watcher - it has no parameters of any |
2640 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2648 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2641 | trust me. |
2649 | trust me. |
2642 | |
2650 | |
2643 | =item ev_async_send (loop, ev_async *) |
2651 | =item ev_async_send (loop, ev_async *) |
2644 | |
2652 | |
2645 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2653 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
… | |
… | |
3078 | |
3086 | |
3079 | #define EV_STANDALONE 1 |
3087 | #define EV_STANDALONE 1 |
3080 | #include "ev.h" |
3088 | #include "ev.h" |
3081 | |
3089 | |
3082 | Both header files and implementation files can be compiled with a C++ |
3090 | Both header files and implementation files can be compiled with a C++ |
3083 | compiler (at least, thats a stated goal, and breakage will be treated |
3091 | compiler (at least, that's a stated goal, and breakage will be treated |
3084 | as a bug). |
3092 | as a bug). |
3085 | |
3093 | |
3086 | You need the following files in your source tree, or in a directory |
3094 | You need the following files in your source tree, or in a directory |
3087 | in your include path (e.g. in libev/ when using -Ilibev): |
3095 | in your include path (e.g. in libev/ when using -Ilibev): |
3088 | |
3096 | |
… | |
… | |
3560 | loop, as long as you don't confuse yourself). The only exception is that |
3568 | loop, as long as you don't confuse yourself). The only exception is that |
3561 | you must not do this from C<ev_periodic> reschedule callbacks. |
3569 | you must not do this from C<ev_periodic> reschedule callbacks. |
3562 | |
3570 | |
3563 | Care has been taken to ensure that libev does not keep local state inside |
3571 | Care has been taken to ensure that libev does not keep local state inside |
3564 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3572 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3565 | they do not clal any callbacks. |
3573 | they do not call any callbacks. |
3566 | |
3574 | |
3567 | =head2 COMPILER WARNINGS |
3575 | =head2 COMPILER WARNINGS |
3568 | |
3576 | |
3569 | Depending on your compiler and compiler settings, you might get no or a |
3577 | Depending on your compiler and compiler settings, you might get no or a |
3570 | lot of warnings when compiling libev code. Some people are apparently |
3578 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3604 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3612 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3605 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3613 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3606 | ==2274== still reachable: 256 bytes in 1 blocks. |
3614 | ==2274== still reachable: 256 bytes in 1 blocks. |
3607 | |
3615 | |
3608 | Then there is no memory leak, just as memory accounted to global variables |
3616 | Then there is no memory leak, just as memory accounted to global variables |
3609 | is not a memleak - the memory is still being refernced, and didn't leak. |
3617 | is not a memleak - the memory is still being referenced, and didn't leak. |
3610 | |
3618 | |
3611 | Similarly, under some circumstances, valgrind might report kernel bugs |
3619 | Similarly, under some circumstances, valgrind might report kernel bugs |
3612 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3620 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3613 | although an acceptable workaround has been found here), or it might be |
3621 | although an acceptable workaround has been found here), or it might be |
3614 | confused. |
3622 | confused. |
… | |
… | |
3852 | =back |
3860 | =back |
3853 | |
3861 | |
3854 | |
3862 | |
3855 | =head1 AUTHOR |
3863 | =head1 AUTHOR |
3856 | |
3864 | |
3857 | Marc Lehmann <libev@schmorp.de>. |
3865 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3858 | |
3866 | |