… | |
… | |
66 | |
66 | |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
68 | useful) and you want to force your users to use the one and only event |
68 | useful) and you want to force your users to use the one and only event |
69 | model, you should I<not> use this module. |
69 | model, you should I<not> use this module. |
70 | |
70 | |
|
|
71 | #TODO# |
|
|
72 | |
|
|
73 | Net::IRC3 |
|
|
74 | AnyEvent::HTTPD |
|
|
75 | AnyEvent::DNS |
|
|
76 | IO::AnyEvent |
|
|
77 | Net::FPing |
|
|
78 | Net::XMPP2 |
|
|
79 | Coro |
|
|
80 | |
|
|
81 | AnyEvent::IRC |
|
|
82 | AnyEvent::HTTPD |
|
|
83 | AnyEvent::DNS |
|
|
84 | AnyEvent::Handle |
|
|
85 | AnyEvent::Socket |
|
|
86 | AnyEvent::FPing |
|
|
87 | AnyEvent::XMPP |
|
|
88 | AnyEvent::SNMP |
|
|
89 | Coro |
71 | |
90 | |
72 | =head1 DESCRIPTION |
91 | =head1 DESCRIPTION |
73 | |
92 | |
74 | L<AnyEvent> provides an identical interface to multiple event loops. This |
93 | L<AnyEvent> provides an identical interface to multiple event loops. This |
75 | allows module authors to utilise an event loop without forcing module |
94 | allows module authors to utilise an event loop without forcing module |
… | |
… | |
141 | =head2 I/O WATCHERS |
160 | =head2 I/O WATCHERS |
142 | |
161 | |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
162 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
144 | with the following mandatory key-value pairs as arguments: |
163 | with the following mandatory key-value pairs as arguments: |
145 | |
164 | |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
165 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
166 | for events. C<poll> must be a string that is either C<r> or C<w>, |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
167 | which creates a watcher waiting for "r"eadable or "w"ritable events, |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
168 | respectively. C<cb> is the callback to invoke each time the file handle |
150 | becomes ready. |
169 | becomes ready. |
|
|
170 | |
|
|
171 | Although the callback might get passed parameters, their value and |
|
|
172 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
173 | callbacks cannot use arguments passed to I/O watcher callbacks. |
151 | |
174 | |
152 | The I/O watcher might use the underlying file descriptor or a copy of it. |
175 | The I/O watcher might use the underlying file descriptor or a copy of it. |
153 | You must not close a file handle as long as any watcher is active on the |
176 | You must not close a file handle as long as any watcher is active on the |
154 | underlying file descriptor. |
177 | underlying file descriptor. |
155 | |
178 | |
156 | Some event loops issue spurious readyness notifications, so you should |
179 | Some event loops issue spurious readyness notifications, so you should |
157 | always use non-blocking calls when reading/writing from/to your file |
180 | always use non-blocking calls when reading/writing from/to your file |
158 | handles. |
181 | handles. |
159 | |
|
|
160 | Although the callback might get passed parameters, their value and |
|
|
161 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
162 | callbacks cannot use arguments passed to I/O watcher callbacks. |
|
|
163 | |
182 | |
164 | Example: |
183 | Example: |
165 | |
184 | |
166 | # wait for readability of STDIN, then read a line and disable the watcher |
185 | # wait for readability of STDIN, then read a line and disable the watcher |
167 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
186 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
… | |
… | |
174 | |
193 | |
175 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
194 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
176 | method with the following mandatory arguments: |
195 | method with the following mandatory arguments: |
177 | |
196 | |
178 | C<after> specifies after how many seconds (fractional values are |
197 | C<after> specifies after how many seconds (fractional values are |
179 | supported) should the timer activate. C<cb> the callback to invoke in that |
198 | supported) the callback should be invoked. C<cb> is the callback to invoke |
180 | case. |
199 | in that case. |
|
|
200 | |
|
|
201 | Although the callback might get passed parameters, their value and |
|
|
202 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
203 | callbacks cannot use arguments passed to time watcher callbacks. |
181 | |
204 | |
182 | The timer callback will be invoked at most once: if you want a repeating |
205 | The timer callback will be invoked at most once: if you want a repeating |
183 | timer you have to create a new watcher (this is a limitation by both Tk |
206 | timer you have to create a new watcher (this is a limitation by both Tk |
184 | and Glib). |
207 | and Glib). |
185 | |
|
|
186 | Although the callback might get passed parameters, their value and |
|
|
187 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
188 | callbacks cannot use arguments passed to time watcher callbacks. |
|
|
189 | |
208 | |
190 | Example: |
209 | Example: |
191 | |
210 | |
192 | # fire an event after 7.7 seconds |
211 | # fire an event after 7.7 seconds |
193 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
212 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
… | |
… | |
234 | |
253 | |
235 | You can watch for signals using a signal watcher, C<signal> is the signal |
254 | You can watch for signals using a signal watcher, C<signal> is the signal |
236 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
255 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
237 | be invoked whenever a signal occurs. |
256 | be invoked whenever a signal occurs. |
238 | |
257 | |
|
|
258 | Although the callback might get passed parameters, their value and |
|
|
259 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
260 | callbacks cannot use arguments passed to signal watcher callbacks. |
|
|
261 | |
239 | Multiple signal occurances can be clumped together into one callback |
262 | Multiple signal occurances can be clumped together into one callback |
240 | invocation, and callback invocation will be synchronous. synchronous means |
263 | invocation, and callback invocation will be synchronous. synchronous means |
241 | that it might take a while until the signal gets handled by the process, |
264 | that it might take a while until the signal gets handled by the process, |
242 | but it is guarenteed not to interrupt any other callbacks. |
265 | but it is guarenteed not to interrupt any other callbacks. |
243 | |
266 | |
… | |
… | |
257 | |
280 | |
258 | The child process is specified by the C<pid> argument (if set to C<0>, it |
281 | The child process is specified by the C<pid> argument (if set to C<0>, it |
259 | watches for any child process exit). The watcher will trigger as often |
282 | watches for any child process exit). The watcher will trigger as often |
260 | as status change for the child are received. This works by installing a |
283 | as status change for the child are received. This works by installing a |
261 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
284 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
262 | and exit status (as returned by waitpid). |
285 | and exit status (as returned by waitpid), so unlike other watcher types, |
|
|
286 | you I<can> rely on child watcher callback arguments. |
263 | |
287 | |
264 | There is a slight catch to child watchers, however: you usually start them |
288 | There is a slight catch to child watchers, however: you usually start them |
265 | I<after> the child process was created, and this means the process could |
289 | I<after> the child process was created, and this means the process could |
266 | have exited already (and no SIGCHLD will be sent anymore). |
290 | have exited already (and no SIGCHLD will be sent anymore). |
267 | |
291 | |
… | |
… | |
889 | }); |
913 | }); |
890 | |
914 | |
891 | $quit->wait; |
915 | $quit->wait; |
892 | |
916 | |
893 | |
917 | |
894 | =head1 BENCHMARK |
918 | =head1 BENCHMARKS |
895 | |
919 | |
896 | To give you an idea of the performance and overheads that AnyEvent adds |
920 | To give you an idea of the performance and overheads that AnyEvent adds |
897 | over the event loops themselves (and to give you an impression of the |
921 | over the event loops themselves and to give you an impression of the speed |
898 | speed of various event loops), here is a benchmark of various supported |
922 | of various event loops I prepared some benchmarks. |
899 | event models natively and with anyevent. The benchmark creates a lot of |
923 | |
900 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
924 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
|
|
925 | |
|
|
926 | Here is a benchmark of various supported event models used natively and |
|
|
927 | through anyevent. The benchmark creates a lot of timers (with a zero |
|
|
928 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
901 | become writable, which it is), lets them fire exactly once and destroys |
929 | which it is), lets them fire exactly once and destroys them again. |
902 | them again. |
|
|
903 | |
930 | |
904 | Rewriting the benchmark to use many different sockets instead of using |
931 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
905 | the same filehandle for all I/O watchers results in a much longer runtime |
932 | distribution. |
906 | (socket creation is expensive), but qualitatively the same figures, so it |
|
|
907 | was not used. |
|
|
908 | |
933 | |
909 | =head2 Explanation of the columns |
934 | =head3 Explanation of the columns |
910 | |
935 | |
911 | I<watcher> is the number of event watchers created/destroyed. Since |
936 | I<watcher> is the number of event watchers created/destroyed. Since |
912 | different event models feature vastly different performances, each event |
937 | different event models feature vastly different performances, each event |
913 | loop was given a number of watchers so that overall runtime is acceptable |
938 | loop was given a number of watchers so that overall runtime is acceptable |
914 | and similar between tested event loop (and keep them from crashing): Glib |
939 | and similar between tested event loop (and keep them from crashing): Glib |
… | |
… | |
930 | signal the end of this phase. |
955 | signal the end of this phase. |
931 | |
956 | |
932 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
957 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
933 | watcher. |
958 | watcher. |
934 | |
959 | |
935 | =head2 Results |
960 | =head3 Results |
936 | |
961 | |
937 | name watchers bytes create invoke destroy comment |
962 | name watchers bytes create invoke destroy comment |
938 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
963 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
939 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
964 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
940 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
965 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
941 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
966 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
942 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
967 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
943 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
968 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
944 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
969 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
945 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
970 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
946 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
971 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
947 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
972 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
948 | |
973 | |
949 | =head2 Discussion |
974 | =head3 Discussion |
950 | |
975 | |
951 | The benchmark does I<not> measure scalability of the event loop very |
976 | The benchmark does I<not> measure scalability of the event loop very |
952 | well. For example, a select-based event loop (such as the pure perl one) |
977 | well. For example, a select-based event loop (such as the pure perl one) |
953 | can never compete with an event loop that uses epoll when the number of |
978 | can never compete with an event loop that uses epoll when the number of |
954 | file descriptors grows high. In this benchmark, all events become ready at |
979 | file descriptors grows high. In this benchmark, all events become ready at |
955 | the same time, so select/poll-based implementations get an unnatural speed |
980 | the same time, so select/poll-based implementations get an unnatural speed |
956 | boost. |
981 | boost. |
957 | |
982 | |
|
|
983 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
984 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
985 | the time - usually it takes longer. This puts event loops tested with a |
|
|
986 | higher number of watchers at a disadvantage. |
|
|
987 | |
|
|
988 | To put the range of results into perspective, consider that on the |
|
|
989 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
990 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
991 | cycles with POE. |
|
|
992 | |
958 | C<EV> is the sole leader regarding speed and memory use, which are both |
993 | C<EV> is the sole leader regarding speed and memory use, which are both |
959 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
994 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
960 | far less memory than any other event loop and is still faster than Event |
995 | far less memory than any other event loop and is still faster than Event |
961 | natively. |
996 | natively. |
962 | |
997 | |
963 | The pure perl implementation is hit in a few sweet spots (both the |
998 | The pure perl implementation is hit in a few sweet spots (both the |
964 | zero timeout and the use of a single fd hit optimisations in the perl |
999 | constant timeout and the use of a single fd hit optimisations in the perl |
965 | interpreter and the backend itself, and all watchers become ready at the |
1000 | interpreter and the backend itself). Nevertheless this shows that it |
966 | same time). Nevertheless this shows that it adds very little overhead in |
1001 | adds very little overhead in itself. Like any select-based backend its |
967 | itself. Like any select-based backend its performance becomes really bad |
1002 | performance becomes really bad with lots of file descriptors (and few of |
968 | with lots of file descriptors (and few of them active), of course, but |
1003 | them active), of course, but this was not subject of this benchmark. |
969 | this was not subject of this benchmark. |
|
|
970 | |
1004 | |
971 | The C<Event> module has a relatively high setup and callback invocation cost, |
1005 | The C<Event> module has a relatively high setup and callback invocation |
972 | but overall scores on the third place. |
1006 | cost, but overall scores in on the third place. |
973 | |
1007 | |
974 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
1008 | C<Glib>'s memory usage is quite a bit higher, but it features a |
975 | faster callback invocation and overall ends up in the same class as |
1009 | faster callback invocation and overall ends up in the same class as |
976 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1010 | C<Event>. However, Glib scales extremely badly, doubling the number of |
977 | watchers increases the processing time by more than a factor of four, |
1011 | watchers increases the processing time by more than a factor of four, |
978 | making it completely unusable when using larger numbers of watchers |
1012 | making it completely unusable when using larger numbers of watchers |
979 | (note that only a single file descriptor was used in the benchmark, so |
1013 | (note that only a single file descriptor was used in the benchmark, so |
… | |
… | |
982 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
1016 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
983 | more than 2000 watchers is a big setback, however, as correctness takes |
1017 | more than 2000 watchers is a big setback, however, as correctness takes |
984 | precedence over speed. Nevertheless, its performance is surprising, as the |
1018 | precedence over speed. Nevertheless, its performance is surprising, as the |
985 | file descriptor is dup()ed for each watcher. This shows that the dup() |
1019 | file descriptor is dup()ed for each watcher. This shows that the dup() |
986 | employed by some adaptors is not a big performance issue (it does incur a |
1020 | employed by some adaptors is not a big performance issue (it does incur a |
987 | hidden memory cost inside the kernel, though, that is not reflected in the |
1021 | hidden memory cost inside the kernel which is not reflected in the figures |
988 | figures above). |
1022 | above). |
989 | |
1023 | |
990 | C<POE>, regardless of underlying event loop (wether using its pure perl |
1024 | C<POE>, regardless of underlying event loop (whether using its pure |
991 | select-based backend or the Event module) shows abysmal performance and |
1025 | perl select-based backend or the Event module, the POE-EV backend |
|
|
1026 | couldn't be tested because it wasn't working) shows abysmal performance |
992 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
1027 | and memory usage: Watchers use almost 30 times as much memory as |
993 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
1028 | EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1029 | requirements are caused by requiring a session for each watcher). Watcher |
994 | invocation is almost 900 times slower than with AnyEvent's pure perl |
1030 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
995 | implementation. The design of the POE adaptor class in AnyEvent can not |
1031 | implementation. The design of the POE adaptor class in AnyEvent can not |
996 | really account for this, as session creation overhead is small compared |
1032 | really account for this, as session creation overhead is small compared |
997 | to execution of the state machine, which is coded pretty optimally within |
1033 | to execution of the state machine, which is coded pretty optimally within |
998 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
1034 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
999 | |
1035 | |
1000 | =head2 Summary |
1036 | =head3 Summary |
1001 | |
1037 | |
|
|
1038 | =over 4 |
|
|
1039 | |
1002 | Using EV through AnyEvent is faster than any other event loop, but most |
1040 | =item * Using EV through AnyEvent is faster than any other event loop |
1003 | event loops have acceptable performance with or without AnyEvent. |
1041 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1042 | performance with or without AnyEvent. |
1004 | |
1043 | |
1005 | The overhead AnyEvent adds is usually much smaller than the overhead of |
1044 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
1006 | the actual event loop, only with extremely fast event loops such as the EV |
1045 | the actual event loop, only with extremely fast event loops such as EV |
1007 | adds AnyEvent significant overhead. |
1046 | adds AnyEvent significant overhead. |
1008 | |
1047 | |
1009 | And you should simply avoid POE like the plague if you want performance or |
1048 | =item * You should avoid POE like the plague if you want performance or |
1010 | reasonable memory usage. |
1049 | reasonable memory usage. |
|
|
1050 | |
|
|
1051 | =back |
|
|
1052 | |
|
|
1053 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1054 | |
|
|
1055 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1056 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1057 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1058 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1059 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1060 | |
|
|
1061 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1062 | are active at any one point (so there is a constant number of active |
|
|
1063 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1064 | timeout is reset each time something is read because that reflects how |
|
|
1065 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1066 | |
|
|
1067 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1068 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1069 | connections, most of which are idle at any one point in time. |
|
|
1070 | |
|
|
1071 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1072 | distribution. |
|
|
1073 | |
|
|
1074 | =head3 Explanation of the columns |
|
|
1075 | |
|
|
1076 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1077 | each server has a read and write socket end). |
|
|
1078 | |
|
|
1079 | I<create> is the time it takes to create a socketpair (which is |
|
|
1080 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1081 | |
|
|
1082 | I<request>, the most important value, is the time it takes to handle a |
|
|
1083 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1084 | it to another server. This includes deleting the old timeout and creating |
|
|
1085 | a new one that moves the timeout into the future. |
|
|
1086 | |
|
|
1087 | =head3 Results |
|
|
1088 | |
|
|
1089 | name sockets create request |
|
|
1090 | EV 20000 69.01 11.16 |
|
|
1091 | Perl 20000 75.28 112.76 |
|
|
1092 | Event 20000 212.62 257.32 |
|
|
1093 | Glib 20000 651.16 1896.30 |
|
|
1094 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1095 | |
|
|
1096 | =head3 Discussion |
|
|
1097 | |
|
|
1098 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1099 | particular event loop. |
|
|
1100 | |
|
|
1101 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1102 | is relatively high, though. |
|
|
1103 | |
|
|
1104 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1105 | loops Event and Glib. |
|
|
1106 | |
|
|
1107 | Event suffers from high setup time as well (look at its code and you will |
|
|
1108 | understand why). Callback invocation also has a high overhead compared to |
|
|
1109 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1110 | uses select or poll in basically all documented configurations. |
|
|
1111 | |
|
|
1112 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1113 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1114 | |
|
|
1115 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1116 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1117 | it uses a C-based event loop in this case. |
|
|
1118 | |
|
|
1119 | =head3 Summary |
|
|
1120 | |
|
|
1121 | =over 4 |
|
|
1122 | |
|
|
1123 | =item * The pure perl implementation performs extremely well, considering |
|
|
1124 | that it uses select. |
|
|
1125 | |
|
|
1126 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1127 | |
|
|
1128 | =back |
|
|
1129 | |
|
|
1130 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1131 | |
|
|
1132 | While event loops should scale (and select-based ones do not...) even to |
|
|
1133 | large servers, most programs we (or I :) actually write have only a few |
|
|
1134 | I/O watchers. |
|
|
1135 | |
|
|
1136 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1137 | case, but it uses only eight "servers", of which three are active at any |
|
|
1138 | one time. This should reflect performance for a small server relatively |
|
|
1139 | well. |
|
|
1140 | |
|
|
1141 | The columns are identical to the previous table. |
|
|
1142 | |
|
|
1143 | =head3 Results |
|
|
1144 | |
|
|
1145 | name sockets create request |
|
|
1146 | EV 16 20.00 6.54 |
|
|
1147 | Event 16 81.27 35.86 |
|
|
1148 | Glib 16 32.63 15.48 |
|
|
1149 | Perl 16 24.62 162.37 |
|
|
1150 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1151 | |
|
|
1152 | =head3 Discussion |
|
|
1153 | |
|
|
1154 | The benchmark tries to test the performance of a typical small |
|
|
1155 | server. While knowing how various event loops perform is interesting, keep |
|
|
1156 | in mind that their overhead in this case is usually not as important, due |
|
|
1157 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1158 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1159 | them). |
|
|
1160 | |
|
|
1161 | EV is again fastest. |
|
|
1162 | |
|
|
1163 | The C-based event loops Event and Glib come in second this time, as the |
|
|
1164 | overhead of running an iteration is much smaller in C than in Perl (little |
|
|
1165 | code to execute in the inner loop, and perl's function calling overhead is |
|
|
1166 | high, and updating all the data structures is costly). |
|
|
1167 | |
|
|
1168 | The pure perl event loop is much slower, but still competitive. |
|
|
1169 | |
|
|
1170 | POE also performs much better in this case, but is is still far behind the |
|
|
1171 | others. |
|
|
1172 | |
|
|
1173 | =head3 Summary |
|
|
1174 | |
|
|
1175 | =over 4 |
|
|
1176 | |
|
|
1177 | =item * C-based event loops perform very well with small number of |
|
|
1178 | watchers, as the management overhead dominates. |
|
|
1179 | |
|
|
1180 | =back |
1011 | |
1181 | |
1012 | |
1182 | |
1013 | =head1 FORK |
1183 | =head1 FORK |
1014 | |
1184 | |
1015 | Most event libraries are not fork-safe. The ones who are usually are |
1185 | Most event libraries are not fork-safe. The ones who are usually are |