… | |
… | |
64 | |
64 | |
65 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
66 | |
66 | |
67 | The newest version of this document is also available as an html-formatted |
67 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
68 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
70 | |
70 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
74 | |
74 | |
… | |
… | |
117 | to the C<double> type in C, and when you need to do any calculations on |
117 | to the C<double> type in C, and when you need to do any calculations on |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
119 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
120 | throughout libev. |
121 | |
121 | |
|
|
122 | =head1 ERROR HANDLING |
|
|
123 | |
|
|
124 | Libev knows three classes of errors: operating system errors, usage errors |
|
|
125 | and internal errors (bugs). |
|
|
126 | |
|
|
127 | When libev catches an operating system error it cannot handle (for example |
|
|
128 | a syscall indicating a condition libev cannot fix), it calls the callback |
|
|
129 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
|
|
130 | abort. The default is to print a diagnostic message and to call C<abort |
|
|
131 | ()>. |
|
|
132 | |
|
|
133 | When libev detects a usage error such as a negative timer interval, then |
|
|
134 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
|
|
135 | so C<NDEBUG> will disable this checking): these are programming errors in |
|
|
136 | the libev caller and need to be fixed there. |
|
|
137 | |
|
|
138 | Libev also has a few internal error-checking C<assert>ions, and also has |
|
|
139 | extensive consistency checking code. These do not trigger under normal |
|
|
140 | circumstances, as they indicate either a bug in libev or worse. |
|
|
141 | |
|
|
142 | |
122 | =head1 GLOBAL FUNCTIONS |
143 | =head1 GLOBAL FUNCTIONS |
123 | |
144 | |
124 | These functions can be called anytime, even before initialising the |
145 | These functions can be called anytime, even before initialising the |
125 | library in any way. |
146 | library in any way. |
126 | |
147 | |
… | |
… | |
336 | To get good performance out of this backend you need a high amount of |
357 | To get good performance out of this backend you need a high amount of |
337 | parallelity (most of the file descriptors should be busy). If you are |
358 | parallelity (most of the file descriptors should be busy). If you are |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
339 | connections as possible during one iteration. You might also want to have |
360 | connections as possible during one iteration. You might also want to have |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
341 | readyness notifications you get per iteration. |
362 | readiness notifications you get per iteration. |
342 | |
363 | |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
344 | |
365 | |
345 | And this is your standard poll(2) backend. It's more complicated |
366 | And this is your standard poll(2) backend. It's more complicated |
346 | than select, but handles sparse fds better and has no artificial |
367 | than select, but handles sparse fds better and has no artificial |
… | |
… | |
425 | While this backend scales well, it requires one system call per active |
446 | While this backend scales well, it requires one system call per active |
426 | file descriptor per loop iteration. For small and medium numbers of file |
447 | file descriptor per loop iteration. For small and medium numbers of file |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
428 | might perform better. |
449 | might perform better. |
429 | |
450 | |
430 | On the positive side, ignoring the spurious readyness notifications, this |
451 | On the positive side, ignoring the spurious readiness notifications, this |
431 | backend actually performed to specification in all tests and is fully |
452 | backend actually performed to specification in all tests and is fully |
432 | embeddable, which is a rare feat among the OS-specific backends. |
453 | embeddable, which is a rare feat among the OS-specific backends. |
433 | |
454 | |
434 | =item C<EVBACKEND_ALL> |
455 | =item C<EVBACKEND_ALL> |
435 | |
456 | |
… | |
… | |
689 | interval to a value near C<0.1> or so, which is often enough for |
710 | interval to a value near C<0.1> or so, which is often enough for |
690 | interactive servers (of course not for games), likewise for timeouts. It |
711 | interactive servers (of course not for games), likewise for timeouts. It |
691 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
712 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
692 | as this approsaches the timing granularity of most systems. |
713 | as this approsaches the timing granularity of most systems. |
693 | |
714 | |
|
|
715 | =item ev_loop_verify (loop) |
|
|
716 | |
|
|
717 | This function only does something when C<EV_VERIFY> support has been |
|
|
718 | compiled in. It tries to go through all internal structures and checks |
|
|
719 | them for validity. If anything is found to be inconsistent, it will print |
|
|
720 | an error message to standard error and call C<abort ()>. |
|
|
721 | |
|
|
722 | This can be used to catch bugs inside libev itself: under normal |
|
|
723 | circumstances, this function will never abort as of course libev keeps its |
|
|
724 | data structures consistent. |
|
|
725 | |
694 | =back |
726 | =back |
695 | |
727 | |
696 | |
728 | |
697 | =head1 ANATOMY OF A WATCHER |
729 | =head1 ANATOMY OF A WATCHER |
698 | |
730 | |
… | |
… | |
1032 | If you must do this, then force the use of a known-to-be-good backend |
1064 | If you must do this, then force the use of a known-to-be-good backend |
1033 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1065 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1034 | C<EVBACKEND_POLL>). |
1066 | C<EVBACKEND_POLL>). |
1035 | |
1067 | |
1036 | Another thing you have to watch out for is that it is quite easy to |
1068 | Another thing you have to watch out for is that it is quite easy to |
1037 | receive "spurious" readyness notifications, that is your callback might |
1069 | receive "spurious" readiness notifications, that is your callback might |
1038 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1070 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1039 | because there is no data. Not only are some backends known to create a |
1071 | because there is no data. Not only are some backends known to create a |
1040 | lot of those (for example solaris ports), it is very easy to get into |
1072 | lot of those (for example solaris ports), it is very easy to get into |
1041 | this situation even with a relatively standard program structure. Thus |
1073 | this situation even with a relatively standard program structure. Thus |
1042 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1074 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
… | |
… | |
1151 | |
1183 | |
1152 | Timer watchers are simple relative timers that generate an event after a |
1184 | Timer watchers are simple relative timers that generate an event after a |
1153 | given time, and optionally repeating in regular intervals after that. |
1185 | given time, and optionally repeating in regular intervals after that. |
1154 | |
1186 | |
1155 | The timers are based on real time, that is, if you register an event that |
1187 | The timers are based on real time, that is, if you register an event that |
1156 | times out after an hour and you reset your system clock to last years |
1188 | times out after an hour and you reset your system clock to january last |
1157 | time, it will still time out after (roughly) and hour. "Roughly" because |
1189 | year, it will still time out after (roughly) and hour. "Roughly" because |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1190 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1159 | monotonic clock option helps a lot here). |
1191 | monotonic clock option helps a lot here). |
1160 | |
1192 | |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1193 | The relative timeouts are calculated relative to the C<ev_now ()> |
1162 | time. This is usually the right thing as this timestamp refers to the time |
1194 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1164 | you suspect event processing to be delayed and you I<need> to base the timeout |
1196 | you suspect event processing to be delayed and you I<need> to base the timeout |
1165 | on the current time, use something like this to adjust for this: |
1197 | on the current time, use something like this to adjust for this: |
1166 | |
1198 | |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1199 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1168 | |
1200 | |
1169 | The callback is guarenteed to be invoked only when its timeout has passed, |
1201 | The callback is guarenteed to be invoked only after its timeout has passed, |
1170 | but if multiple timers become ready during the same loop iteration then |
1202 | but if multiple timers become ready during the same loop iteration then |
1171 | order of execution is undefined. |
1203 | order of execution is undefined. |
1172 | |
1204 | |
1173 | =head3 Watcher-Specific Functions and Data Members |
1205 | =head3 Watcher-Specific Functions and Data Members |
1174 | |
1206 | |
… | |
… | |
1176 | |
1208 | |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1209 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1178 | |
1210 | |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1211 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1180 | |
1212 | |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1213 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1182 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1214 | is C<0.>, then it will automatically be stopped once the timeout is |
1183 | timer will automatically be configured to trigger again C<repeat> seconds |
1215 | reached. If it is positive, then the timer will automatically be |
1184 | later, again, and again, until stopped manually. |
1216 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1217 | until stopped manually. |
1185 | |
1218 | |
1186 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1219 | The timer itself will do a best-effort at avoiding drift, that is, if |
1187 | configure a timer to trigger every 10 seconds, then it will trigger at |
1220 | you configure a timer to trigger every 10 seconds, then it will normally |
1188 | exactly 10 second intervals. If, however, your program cannot keep up with |
1221 | trigger at exactly 10 second intervals. If, however, your program cannot |
1189 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1222 | keep up with the timer (because it takes longer than those 10 seconds to |
1190 | timer will not fire more than once per event loop iteration. |
1223 | do stuff) the timer will not fire more than once per event loop iteration. |
1191 | |
1224 | |
1192 | =item ev_timer_again (loop, ev_timer *) |
1225 | =item ev_timer_again (loop, ev_timer *) |
1193 | |
1226 | |
1194 | This will act as if the timer timed out and restart it again if it is |
1227 | This will act as if the timer timed out and restart it again if it is |
1195 | repeating. The exact semantics are: |
1228 | repeating. The exact semantics are: |
… | |
… | |
1272 | Periodic watchers are also timers of a kind, but they are very versatile |
1305 | Periodic watchers are also timers of a kind, but they are very versatile |
1273 | (and unfortunately a bit complex). |
1306 | (and unfortunately a bit complex). |
1274 | |
1307 | |
1275 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1308 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1276 | but on wallclock time (absolute time). You can tell a periodic watcher |
1309 | but on wallclock time (absolute time). You can tell a periodic watcher |
1277 | to trigger "at" some specific point in time. For example, if you tell a |
1310 | to trigger after some specific point in time. For example, if you tell a |
1278 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1311 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1279 | + 10.>) and then reset your system clock to the last year, then it will |
1312 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1313 | clock to january of the previous year, then it will take more than year |
1280 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1314 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1281 | roughly 10 seconds later). |
1315 | roughly 10 seconds later as it uses a relative timeout). |
1282 | |
1316 | |
1283 | They can also be used to implement vastly more complex timers, such as |
1317 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1284 | triggering an event on each midnight, local time or other, complicated, |
1318 | such as triggering an event on each "midnight, local time", or other |
1285 | rules. |
1319 | complicated, rules. |
1286 | |
1320 | |
1287 | As with timers, the callback is guarenteed to be invoked only when the |
1321 | As with timers, the callback is guarenteed to be invoked only when the |
1288 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1322 | time (C<at>) has passed, but if multiple periodic timers become ready |
1289 | during the same loop iteration then order of execution is undefined. |
1323 | during the same loop iteration then order of execution is undefined. |
1290 | |
1324 | |
1291 | =head3 Watcher-Specific Functions and Data Members |
1325 | =head3 Watcher-Specific Functions and Data Members |
1292 | |
1326 | |
1293 | =over 4 |
1327 | =over 4 |
… | |
… | |
1301 | |
1335 | |
1302 | =over 4 |
1336 | =over 4 |
1303 | |
1337 | |
1304 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1338 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1305 | |
1339 | |
1306 | In this configuration the watcher triggers an event at the wallclock time |
1340 | In this configuration the watcher triggers an event after the wallclock |
1307 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1341 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1308 | that is, if it is to be run at January 1st 2011 then it will run when the |
1342 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1309 | system time reaches or surpasses this time. |
1343 | run when the system time reaches or surpasses this time. |
1310 | |
1344 | |
1311 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1345 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1312 | |
1346 | |
1313 | In this mode the watcher will always be scheduled to time out at the next |
1347 | In this mode the watcher will always be scheduled to time out at the next |
1314 | C<at + N * interval> time (for some integer N, which can also be negative) |
1348 | C<at + N * interval> time (for some integer N, which can also be negative) |
1315 | and then repeat, regardless of any time jumps. |
1349 | and then repeat, regardless of any time jumps. |
1316 | |
1350 | |
1317 | This can be used to create timers that do not drift with respect to system |
1351 | This can be used to create timers that do not drift with respect to system |
1318 | time: |
1352 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1353 | the hour: |
1319 | |
1354 | |
1320 | ev_periodic_set (&periodic, 0., 3600., 0); |
1355 | ev_periodic_set (&periodic, 0., 3600., 0); |
1321 | |
1356 | |
1322 | This doesn't mean there will always be 3600 seconds in between triggers, |
1357 | This doesn't mean there will always be 3600 seconds in between triggers, |
1323 | but only that the the callback will be called when the system time shows a |
1358 | but only that the the callback will be called when the system time shows a |
… | |
… | |
1328 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1329 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1364 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1330 | |
1365 | |
1331 | For numerical stability it is preferable that the C<at> value is near |
1366 | For numerical stability it is preferable that the C<at> value is near |
1332 | C<ev_now ()> (the current time), but there is no range requirement for |
1367 | C<ev_now ()> (the current time), but there is no range requirement for |
1333 | this value. |
1368 | this value, and in fact is often specified as zero. |
|
|
1369 | |
|
|
1370 | Note also that there is an upper limit to how often a timer can fire (cpu |
|
|
1371 | speed for example), so if C<interval> is very small then timing stability |
|
|
1372 | will of course detoriate. Libev itself tries to be exact to be about one |
|
|
1373 | millisecond (if the OS supports it and the machine is fast enough). |
1334 | |
1374 | |
1335 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1375 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1336 | |
1376 | |
1337 | In this mode the values for C<interval> and C<at> are both being |
1377 | In this mode the values for C<interval> and C<at> are both being |
1338 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1378 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1339 | reschedule callback will be called with the watcher as first, and the |
1379 | reschedule callback will be called with the watcher as first, and the |
1340 | current time as second argument. |
1380 | current time as second argument. |
1341 | |
1381 | |
1342 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1382 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1343 | ever, or make any event loop modifications>. If you need to stop it, |
1383 | ever, or make ANY event loop modifications whatsoever>. |
1344 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1345 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1346 | |
1384 | |
|
|
1385 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1386 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1387 | only event loop modification you are allowed to do). |
|
|
1388 | |
1347 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1389 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1348 | ev_tstamp now)>, e.g.: |
1390 | *w, ev_tstamp now)>, e.g.: |
1349 | |
1391 | |
1350 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1392 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1351 | { |
1393 | { |
1352 | return now + 60.; |
1394 | return now + 60.; |
1353 | } |
1395 | } |
… | |
… | |
1355 | It must return the next time to trigger, based on the passed time value |
1397 | It must return the next time to trigger, based on the passed time value |
1356 | (that is, the lowest time value larger than to the second argument). It |
1398 | (that is, the lowest time value larger than to the second argument). It |
1357 | will usually be called just before the callback will be triggered, but |
1399 | will usually be called just before the callback will be triggered, but |
1358 | might be called at other times, too. |
1400 | might be called at other times, too. |
1359 | |
1401 | |
1360 | NOTE: I<< This callback must always return a time that is later than the |
1402 | NOTE: I<< This callback must always return a time that is higher than or |
1361 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1403 | equal to the passed C<now> value >>. |
1362 | |
1404 | |
1363 | This can be used to create very complex timers, such as a timer that |
1405 | This can be used to create very complex timers, such as a timer that |
1364 | triggers on each midnight, local time. To do this, you would calculate the |
1406 | triggers on "next midnight, local time". To do this, you would calculate the |
1365 | next midnight after C<now> and return the timestamp value for this. How |
1407 | next midnight after C<now> and return the timestamp value for this. How |
1366 | you do this is, again, up to you (but it is not trivial, which is the main |
1408 | you do this is, again, up to you (but it is not trivial, which is the main |
1367 | reason I omitted it as an example). |
1409 | reason I omitted it as an example). |
1368 | |
1410 | |
1369 | =back |
1411 | =back |
… | |
… | |
1657 | calls your callback, which does something. When there is another update |
1699 | calls your callback, which does something. When there is another update |
1658 | within the same second, C<ev_stat> will be unable to detect it as the stat |
1700 | within the same second, C<ev_stat> will be unable to detect it as the stat |
1659 | data does not change. |
1701 | data does not change. |
1660 | |
1702 | |
1661 | The solution to this is to delay acting on a change for slightly more |
1703 | The solution to this is to delay acting on a change for slightly more |
1662 | than second (or till slightly after the next full second boundary), using |
1704 | than a second (or till slightly after the next full second boundary), using |
1663 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1705 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1664 | ev_timer_again (loop, w)>). |
1706 | ev_timer_again (loop, w)>). |
1665 | |
1707 | |
1666 | The C<.02> offset is added to work around small timing inconsistencies |
1708 | The C<.02> offset is added to work around small timing inconsistencies |
1667 | of some operating systems (where the second counter of the current time |
1709 | of some operating systems (where the second counter of the current time |
… | |
… | |
2980 | defined to be C<0>, then they are not. |
3022 | defined to be C<0>, then they are not. |
2981 | |
3023 | |
2982 | =item EV_MINIMAL |
3024 | =item EV_MINIMAL |
2983 | |
3025 | |
2984 | If you need to shave off some kilobytes of code at the expense of some |
3026 | If you need to shave off some kilobytes of code at the expense of some |
2985 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3027 | speed, define this symbol to C<1>. Currently this is used to override some |
2986 | some inlining decisions, saves roughly 30% codesize of amd64. |
3028 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
3029 | much smaller 2-heap for timer management over the default 4-heap. |
2987 | |
3030 | |
2988 | =item EV_PID_HASHSIZE |
3031 | =item EV_PID_HASHSIZE |
2989 | |
3032 | |
2990 | C<ev_child> watchers use a small hash table to distribute workload by |
3033 | C<ev_child> watchers use a small hash table to distribute workload by |
2991 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3034 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2997 | C<ev_stat> watchers use a small hash table to distribute workload by |
3040 | C<ev_stat> watchers use a small hash table to distribute workload by |
2998 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3041 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2999 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3042 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3000 | watchers you might want to increase this value (I<must> be a power of |
3043 | watchers you might want to increase this value (I<must> be a power of |
3001 | two). |
3044 | two). |
|
|
3045 | |
|
|
3046 | =item EV_USE_4HEAP |
|
|
3047 | |
|
|
3048 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3049 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3050 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3051 | noticably faster performance with many (thousands) of watchers. |
|
|
3052 | |
|
|
3053 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3054 | (disabled). |
|
|
3055 | |
|
|
3056 | =item EV_HEAP_CACHE_AT |
|
|
3057 | |
|
|
3058 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3059 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3060 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3061 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3062 | but avoids random read accesses on heap changes. This improves performance |
|
|
3063 | noticably with with many (hundreds) of watchers. |
|
|
3064 | |
|
|
3065 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3066 | (disabled). |
|
|
3067 | |
|
|
3068 | =item EV_VERIFY |
|
|
3069 | |
|
|
3070 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3071 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3072 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3073 | called. If set to C<2>, then the internal verification code will be |
|
|
3074 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3075 | verification code will be called very frequently, which will slow down |
|
|
3076 | libev considerably. |
|
|
3077 | |
|
|
3078 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3079 | C<0.> |
3002 | |
3080 | |
3003 | =item EV_COMMON |
3081 | =item EV_COMMON |
3004 | |
3082 | |
3005 | By default, all watchers have a C<void *data> member. By redefining |
3083 | By default, all watchers have a C<void *data> member. By redefining |
3006 | this macro to a something else you can include more and other types of |
3084 | this macro to a something else you can include more and other types of |
… | |
… | |
3176 | correct watcher to remove. The lists are usually short (you don't usually |
3254 | correct watcher to remove. The lists are usually short (you don't usually |
3177 | have many watchers waiting for the same fd or signal). |
3255 | have many watchers waiting for the same fd or signal). |
3178 | |
3256 | |
3179 | =item Finding the next timer in each loop iteration: O(1) |
3257 | =item Finding the next timer in each loop iteration: O(1) |
3180 | |
3258 | |
3181 | By virtue of using a binary heap, the next timer is always found at the |
3259 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3182 | beginning of the storage array. |
3260 | fixed position in the storage array. |
3183 | |
3261 | |
3184 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3262 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3185 | |
3263 | |
3186 | A change means an I/O watcher gets started or stopped, which requires |
3264 | A change means an I/O watcher gets started or stopped, which requires |
3187 | libev to recalculate its status (and possibly tell the kernel, depending |
3265 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
3228 | |
3306 | |
3229 | Due to the many, low, and arbitrary limits on the win32 platform and |
3307 | Due to the many, low, and arbitrary limits on the win32 platform and |
3230 | the abysmal performance of winsockets, using a large number of sockets |
3308 | the abysmal performance of winsockets, using a large number of sockets |
3231 | is not recommended (and not reasonable). If your program needs to use |
3309 | is not recommended (and not reasonable). If your program needs to use |
3232 | more than a hundred or so sockets, then likely it needs to use a totally |
3310 | more than a hundred or so sockets, then likely it needs to use a totally |
3233 | different implementation for windows, as libev offers the POSIX readyness |
3311 | different implementation for windows, as libev offers the POSIX readiness |
3234 | notification model, which cannot be implemented efficiently on windows |
3312 | notification model, which cannot be implemented efficiently on windows |
3235 | (microsoft monopoly games). |
3313 | (microsoft monopoly games). |
3236 | |
3314 | |
3237 | =over 4 |
3315 | =over 4 |
3238 | |
3316 | |
3239 | =item The winsocket select function |
3317 | =item The winsocket select function |
3240 | |
3318 | |
3241 | The winsocket C<select> function doesn't follow POSIX in that it requires |
3319 | The winsocket C<select> function doesn't follow POSIX in that it |
3242 | socket I<handles> and not socket I<file descriptors>. This makes select |
3320 | requires socket I<handles> and not socket I<file descriptors> (it is |
3243 | very inefficient, and also requires a mapping from file descriptors |
3321 | also extremely buggy). This makes select very inefficient, and also |
3244 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
3322 | requires a mapping from file descriptors to socket handles. See the |
3245 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
3323 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
3246 | symbols for more info. |
3324 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
3247 | |
3325 | |
3248 | The configuration for a "naked" win32 using the microsoft runtime |
3326 | The configuration for a "naked" win32 using the microsoft runtime |
3249 | libraries and raw winsocket select is: |
3327 | libraries and raw winsocket select is: |
3250 | |
3328 | |
3251 | #define EV_USE_SELECT 1 |
3329 | #define EV_USE_SELECT 1 |
… | |
… | |
3319 | is still at least 31 bits everywhere, which is enough for hundreds of |
3397 | is still at least 31 bits everywhere, which is enough for hundreds of |
3320 | millions of watchers. |
3398 | millions of watchers. |
3321 | |
3399 | |
3322 | =item C<double> must hold a time value in seconds with enough accuracy |
3400 | =item C<double> must hold a time value in seconds with enough accuracy |
3323 | |
3401 | |
3324 | The type C<double> is used to represent timestamps. It is required to have |
3402 | The type C<double> is used to represent timestamps. It is required to |
3325 | at least 51 bits of mantissa, which is good enough for at least into the |
3403 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3326 | year 4000. This requirement is fulfilled by implementations implementing |
3404 | enough for at least into the year 4000. This requirement is fulfilled by |
3327 | IEEE 754 (basically all existing ones). |
3405 | implementations implementing IEEE 754 (basically all existing ones). |
3328 | |
3406 | |
3329 | =back |
3407 | =back |
3330 | |
3408 | |
3331 | If you know of other additional requirements drop me a note. |
3409 | If you know of other additional requirements drop me a note. |
3332 | |
3410 | |
3333 | |
3411 | |
|
|
3412 | =head1 COMPILER WARNINGS |
|
|
3413 | |
|
|
3414 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3415 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3416 | scared by this. |
|
|
3417 | |
|
|
3418 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3419 | has different warnings, and each user has different tastes regarding |
|
|
3420 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3421 | targetting a specific compiler and compiler-version. |
|
|
3422 | |
|
|
3423 | Another reason is that some compiler warnings require elaborate |
|
|
3424 | workarounds, or other changes to the code that make it less clear and less |
|
|
3425 | maintainable. |
|
|
3426 | |
|
|
3427 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3428 | wrong (because they don't actually warn about the cindition their message |
|
|
3429 | seems to warn about). |
|
|
3430 | |
|
|
3431 | While libev is written to generate as few warnings as possible, |
|
|
3432 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3433 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3434 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3435 | warnings, not errors, or proof of bugs. |
|
|
3436 | |
|
|
3437 | |
|
|
3438 | =head1 VALGRIND |
|
|
3439 | |
|
|
3440 | Valgrind has a special section here because it is a popular tool that is |
|
|
3441 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3442 | |
|
|
3443 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3444 | in libev, then check twice: If valgrind reports something like: |
|
|
3445 | |
|
|
3446 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3447 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3448 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3449 | |
|
|
3450 | then there is no memory leak. Similarly, under some circumstances, |
|
|
3451 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3452 | might be confused (it is a very good tool, but only a tool). |
|
|
3453 | |
|
|
3454 | If you are unsure about something, feel free to contact the mailing list |
|
|
3455 | with the full valgrind report and an explanation on why you think this is |
|
|
3456 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3457 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3458 | properly. |
|
|
3459 | |
|
|
3460 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3461 | I suggest using suppression lists. |
|
|
3462 | |
|
|
3463 | |
3334 | =head1 AUTHOR |
3464 | =head1 AUTHOR |
3335 | |
3465 | |
3336 | Marc Lehmann <libev@schmorp.de>. |
3466 | Marc Lehmann <libev@schmorp.de>. |
3337 | |
3467 | |