… | |
… | |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
46 | time differences throughout libeio. |
46 | time differences throughout libeio. |
47 | |
47 | |
48 | =head2 FORK SUPPORT |
48 | =head2 FORK SUPPORT |
49 | |
49 | |
50 | Calling C<fork ()> is fully supported by this module. It is implemented in these steps: |
50 | Calling C<fork ()> is fully supported by this module - but you must not |
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51 | rely on this. It is currently implemented in these steps: |
51 | |
52 | |
52 | 1. wait till all requests in "execute" state have been handled |
53 | 1. wait till all requests in "execute" state have been handled |
53 | (basically requests that are already handed over to the kernel). |
54 | (basically requests that are already handed over to the kernel). |
54 | 2. fork |
55 | 2. fork |
55 | 3. in the parent, continue business as usual, done |
56 | 3. in the parent, continue business as usual, done |
56 | 4. in the child, destroy all ready and pending requests and free the |
57 | 4. in the child, destroy all ready and pending requests and free the |
57 | memory used by the worker threads. This gives you a fully empty |
58 | memory used by the worker threads. This gives you a fully empty |
58 | libeio queue. |
59 | libeio queue. |
59 | |
60 | |
60 | Note, however, since libeio does use threads, thr above guarantee doesn't |
61 | Note, however, since libeio does use threads, the above guarantee doesn't |
61 | cover your libc, for example, malloc and other libc functions are not |
62 | cover your libc, for example, malloc and other libc functions are not |
62 | fork-safe, so there is very little you can do after a fork, and in fatc, |
63 | fork-safe, so there is very little you can do after a fork, and in fact, |
63 | the above might crash, and thus change. |
64 | the above might crash, and thus change. |
64 | |
65 | |
65 | =head1 INITIALISATION/INTEGRATION |
66 | =head1 INITIALISATION/INTEGRATION |
66 | |
67 | |
67 | Before you can call any eio functions you first have to initialise the |
68 | Before you can call any eio functions you first have to initialise the |
… | |
… | |
124 | =back |
125 | =back |
125 | |
126 | |
126 | For libev, you would typically use an C<ev_async> watcher: the |
127 | For libev, you would typically use an C<ev_async> watcher: the |
127 | C<want_poll> callback would invoke C<ev_async_send> to wake up the event |
128 | C<want_poll> callback would invoke C<ev_async_send> to wake up the event |
128 | loop. Inside the callback set for the watcher, one would call C<eio_poll |
129 | loop. Inside the callback set for the watcher, one would call C<eio_poll |
129 | ()> (followed by C<ev_async_send> again if C<eio_poll> indicates that not |
130 | ()>. |
130 | all requests have been handled yet). The race is taken care of because |
131 | |
131 | libev resets/rearms the async watcher before calling your callback, |
132 | If C<eio_poll ()> is configured to not handle all results in one go |
132 | and therefore, before calling C<eio_poll>. This might result in (some) |
133 | (i.e. it returns C<-1>) then you should start an idle watcher that calls |
133 | spurious wake-ups, but is generally harmless. |
134 | C<eio_poll> until it returns something C<!= -1>. |
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135 | |
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136 | A full-featured conenctor between libeio and libev would look as follows |
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137 | (if C<eio_poll> is handling all requests, it can of course be simplified a |
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138 | lot by removing the idle watcher logic): |
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139 | |
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140 | static struct ev_loop *loop; |
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141 | static ev_idle repeat_watcher; |
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142 | static ev_async ready_watcher; |
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143 | |
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144 | /* idle watcher callback, only used when eio_poll */ |
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145 | /* didn't handle all results in one call */ |
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146 | static void |
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147 | repeat (EV_P_ ev_idle *w, int revents) |
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148 | { |
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149 | if (eio_poll () != -1) |
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150 | ev_idle_stop (EV_A_ w); |
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151 | } |
|
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152 | |
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153 | /* eio has some results, process them */ |
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154 | static void |
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155 | ready (EV_P_ ev_async *w, int revents) |
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156 | { |
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157 | if (eio_poll () == -1) |
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158 | ev_idle_start (EV_A_ &repeat_watcher); |
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159 | } |
|
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160 | |
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161 | /* wake up the event loop */ |
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162 | static void |
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163 | want_poll (void) |
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164 | { |
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165 | ev_async_send (loop, &ready_watcher) |
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166 | } |
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167 | |
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168 | void |
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169 | my_init_eio () |
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170 | { |
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171 | loop = EV_DEFAULT; |
|
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172 | |
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173 | ev_idle_init (&repeat_watcher, repeat); |
|
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174 | ev_async_init (&ready_watcher, ready); |
|
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175 | ev_async_start (loop &watcher); |
|
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176 | |
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177 | eio_init (want_poll, 0); |
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178 | } |
134 | |
179 | |
135 | For most other event loops, you would typically use a pipe - the event |
180 | For most other event loops, you would typically use a pipe - the event |
136 | loop should be told to wait for read readiness on the read end. In |
181 | loop should be told to wait for read readiness on the read end. In |
137 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
182 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
138 | to read that byte, and in the callback for the read end, you would call |
183 | to read that byte, and in the callback for the read end, you would call |
139 | C<eio_poll>. The race is avoided here because the event loop should invoke |
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140 | your callback again and again until the byte has been read (as the pipe |
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141 | read callback does not read it, only C<done_poll>). |
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142 | |
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143 | =head2 CONFIGURATION |
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144 | |
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145 | The functions in this section can sometimes be useful, but the default |
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146 | configuration will do in most case, so you should skip this section on |
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147 | first reading. |
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148 | |
|
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149 | =over 4 |
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150 | |
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151 | =item eio_set_max_poll_time (eio_tstamp nseconds) |
|
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152 | |
|
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153 | This causes C<eio_poll ()> to return after it has detected that it was |
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154 | running for C<nsecond> seconds or longer (this number can be fractional). |
|
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155 | |
|
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156 | This can be used to limit the amount of time spent handling eio requests, |
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157 | for example, in interactive programs, you might want to limit this time to |
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158 | C<0.01> seconds or so. |
|
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159 | |
|
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160 | Note that: |
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161 | |
|
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162 | a) libeio doesn't know how long your request callbacks take, so the time |
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163 | spent in C<eio_poll> is up to one callback invocation longer then this |
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164 | interval. |
|
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165 | |
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166 | b) this is implemented by calling C<gettimeofday> after each request, |
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167 | which can be costly. |
|
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168 | |
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169 | c) at least one request will be handled. |
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170 | |
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171 | =item eio_set_max_poll_reqs (unsigned int nreqs) |
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172 | |
|
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173 | When C<nreqs> is non-zero, then C<eio_poll> will not handle more than |
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174 | C<nreqs> requests per invocation. This is a less costly way to limit the |
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175 | amount of work done by C<eio_poll> then setting a time limit. |
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176 | |
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177 | If you know your callbacks are generally fast, you could use this to |
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178 | encourage interactiveness in your programs by setting it to C<10>, C<100> |
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179 | or even C<1000>. |
|
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180 | |
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181 | =item eio_set_min_parallel (unsigned int nthreads) |
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182 | |
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183 | Make sure libeio can handle at least this many requests in parallel. It |
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184 | might be able handle more. |
|
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185 | |
|
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186 | =item eio_set_max_parallel (unsigned int nthreads) |
|
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187 | |
|
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188 | Set the maximum number of threads that libeio will spawn. |
|
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189 | |
|
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190 | =item eio_set_max_idle (unsigned int nthreads) |
|
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191 | |
|
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192 | Libeio uses threads internally to handle most requests, and will start and stop threads on demand. |
|
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193 | |
|
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194 | This call can be used to limit the number of idle threads (threads without |
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195 | work to do): libeio will keep some threads idle in preparation for more |
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196 | requests, but never longer than C<nthreads> threads. |
|
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197 | |
|
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198 | In addition to this, libeio will also stop threads when they are idle for |
|
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199 | a few seconds, regardless of this setting. |
|
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200 | |
|
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201 | =item unsigned int eio_nthreads () |
|
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202 | |
|
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203 | Return the number of worker threads currently running. |
|
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204 | |
|
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205 | =item unsigned int eio_nreqs () |
|
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206 | |
|
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207 | Return the number of requests currently handled by libeio. This is the |
|
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208 | total number of requests that have been submitted to libeio, but not yet |
|
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209 | destroyed. |
|
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210 | |
|
|
211 | =item unsigned int eio_nready () |
|
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212 | |
|
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213 | Returns the number of ready requests, i.e. requests that have been |
|
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214 | submitted but have not yet entered the execution phase. |
|
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215 | |
|
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216 | =item unsigned int eio_npending () |
|
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217 | |
|
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218 | Returns the number of pending requests, i.e. requests that have been |
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219 | executed and have results, but have not been finished yet by a call to |
|
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220 | C<eio_poll>). |
184 | C<eio_poll>. |
221 | |
185 | |
222 | =back |
186 | You don't have to take special care in the case C<eio_poll> doesn't handle |
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187 | all requests, as the done callback will not be invoked, so the event loop |
|
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188 | will still signal readyness for the pipe until I<all> results have been |
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189 | processed. |
223 | |
190 | |
224 | |
191 | |
225 | =head1 HIGH LEVEL REQUEST API |
192 | =head1 HIGH LEVEL REQUEST API |
226 | |
193 | |
227 | Libeio has both a high-level API, which consists of calling a request |
194 | Libeio has both a high-level API, which consists of calling a request |
… | |
… | |
234 | |
201 | |
235 | You submit a request by calling the relevant C<eio_TYPE> function with the |
202 | You submit a request by calling the relevant C<eio_TYPE> function with the |
236 | required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> |
203 | required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> |
237 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
204 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
238 | |
205 | |
239 | The return value will either be 0 |
206 | The return value will either be 0, in case something went really wrong |
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207 | (which can basically only happen on very fatal errors, such as C<malloc> |
|
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208 | returning 0, which is rather unlikely), or a pointer to the newly-created |
|
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209 | and submitted C<eio_req *>. |
240 | |
210 | |
241 | The callback will be called with an C<eio_req *> which contains the |
211 | The callback will be called with an C<eio_req *> which contains the |
242 | results of the request. The members you can access inside that structure |
212 | results of the request. The members you can access inside that structure |
243 | vary from request to request, except for: |
213 | vary from request to request, except for: |
244 | |
214 | |
… | |
… | |
296 | abort (); /* something ent wrong, we will all die!!! */ |
266 | abort (); /* something ent wrong, we will all die!!! */ |
297 | |
267 | |
298 | Note that you additionally need to call C<eio_poll> when the C<want_cb> |
268 | Note that you additionally need to call C<eio_poll> when the C<want_cb> |
299 | indicates that requests are ready to be processed. |
269 | indicates that requests are ready to be processed. |
300 | |
270 | |
|
|
271 | =head2 CANCELLING REQUESTS |
|
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272 | |
|
|
273 | Sometimes the need for a request goes away before the request is |
|
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274 | finished. In that case, one can cancel the reqiest by a call to |
|
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275 | C<eio_cancel>: |
|
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276 | |
|
|
277 | =over 4 |
|
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278 | |
|
|
279 | =item eio_cancel (eio_req *req) |
|
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280 | |
|
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281 | Cancel the request. If the request is currently executing it might still |
|
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282 | continue to execute, and in other cases it might still take a while till |
|
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283 | the request is cancelled. |
|
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284 | |
|
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285 | Even if cancelled, the finish callback will still be invoked - the |
|
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286 | callbacks of all cancellable requests need to check whether the request |
|
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287 | has been cancelled by calling C<EIO_CANCELLED (req)>: |
|
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288 | |
|
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289 | static int |
|
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290 | my_eio_cb (eio_req *req) |
|
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291 | { |
|
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292 | if (EIO_CANCELLED (req)) |
|
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293 | return 0; |
|
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294 | } |
|
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295 | |
|
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296 | In addition, cancelled requests will either have C<< req->result >> set to |
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297 | C<-1> and C<errno> to C<ECANCELED>, or otherwise they were successfully |
|
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298 | executed despite being cancelled (e.g. when they have already been |
|
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299 | executed at the time they were cancelled). |
|
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300 | |
|
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301 | =back |
|
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302 | |
301 | =head2 AVAILABLE REQUESTS |
303 | =head2 AVAILABLE REQUESTS |
302 | |
304 | |
303 | The following request functions are available. I<All> of them return the |
305 | The following request functions are available. I<All> of them return the |
304 | C<eio_req *> on success and C<0> on failure, and I<all> of them have the |
306 | C<eio_req *> on success and C<0> on failure, and I<all> of them have the |
305 | same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is |
307 | same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is |
… | |
… | |
307 | custom data value as C<data>. |
309 | custom data value as C<data>. |
308 | |
310 | |
309 | =head3 POSIX API WRAPPERS |
311 | =head3 POSIX API WRAPPERS |
310 | |
312 | |
311 | These requests simply wrap the POSIX call of the same name, with the same |
313 | These requests simply wrap the POSIX call of the same name, with the same |
312 | arguments: |
314 | arguments. If a function is not implemented by the OS and cannot be emulated |
|
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315 | in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>. |
313 | |
316 | |
314 | =over 4 |
317 | =over 4 |
315 | |
318 | |
316 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
319 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
317 | |
320 | |
|
|
321 | =item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data) |
|
|
322 | |
|
|
323 | =item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
|
324 | |
|
|
325 | =item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
|
326 | |
|
|
327 | =item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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328 | |
|
|
329 | =item eio_rmdir (const char *path, int pri, eio_cb cb, void *data) |
|
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330 | |
|
|
331 | =item eio_unlink (const char *path, int pri, eio_cb cb, void *data) |
|
|
332 | |
318 | =item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
333 | =item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
319 | |
334 | |
320 | =item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data) |
|
|
321 | |
|
|
322 | =item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
|
323 | |
|
|
324 | =item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
|
325 | |
|
|
326 | =item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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327 | |
|
|
328 | =item eio_rmdir (const char *path, int pri, eio_cb cb, void *data) |
|
|
329 | |
|
|
330 | =item eio_unlink (const char *path, int pri, eio_cb cb, void *data) |
|
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331 | |
|
|
332 | =item eio_readlink (const char *path, int pri, eio_cb cb, void *data) /* result=ptr2 allocated dynamically */ |
|
|
333 | |
|
|
334 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
|
335 | |
|
|
336 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
|
337 | |
|
|
338 | =item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
|
339 | |
|
|
340 | =item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) |
335 | =item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) |
341 | |
336 | |
342 | =item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
337 | =item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
343 | |
338 | |
344 | =item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
339 | =item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
345 | |
340 | |
346 | =item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
341 | =item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
347 | |
342 | |
348 | =item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
|
349 | |
|
|
350 | =item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) |
343 | =item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) |
351 | |
|
|
352 | =item eio_mlockall (int flags, int pri, eio_cb cb, void *data) |
|
|
353 | |
344 | |
354 | =item eio_close (int fd, int pri, eio_cb cb, void *data) |
345 | =item eio_close (int fd, int pri, eio_cb cb, void *data) |
355 | |
346 | |
356 | =item eio_sync (int pri, eio_cb cb, void *data) |
347 | =item eio_sync (int pri, eio_cb cb, void *data) |
357 | |
348 | |
… | |
… | |
386 | |
377 | |
387 | Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), |
378 | Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), |
388 | so it is advised not to submit multiple requests on the same fd on this |
379 | so it is advised not to submit multiple requests on the same fd on this |
389 | horrible pile of garbage. |
380 | horrible pile of garbage. |
390 | |
381 | |
|
|
382 | =item eio_mlockall (int flags, int pri, eio_cb cb, void *data) |
|
|
383 | |
|
|
384 | Like C<mlockall>, but the flag value constants are called |
|
|
385 | C<EIO_MCL_CURRENT> and C<EIO_MCL_FUTURE>. |
|
|
386 | |
|
|
387 | =item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
|
388 | |
|
|
389 | Just like msync, except that the flag values are called C<EIO_MS_ASYNC>, |
|
|
390 | C<EIO_MS_INVALIDATE> and C<EIO_MS_SYNC>. |
|
|
391 | |
|
|
392 | =item eio_readlink (const char *path, int pri, eio_cb cb, void *data) |
|
|
393 | |
|
|
394 | If successful, the path read by C<readlink(2)> can be accessed via C<< |
|
|
395 | req->ptr2 >> and is I<NOT> null-terminated, with the length specified as |
|
|
396 | C<< req->result >>. |
|
|
397 | |
|
|
398 | if (req->result >= 0) |
|
|
399 | { |
|
|
400 | char *target = strndup ((char *)req->ptr2, req->result); |
|
|
401 | |
|
|
402 | free (target); |
|
|
403 | } |
|
|
404 | |
|
|
405 | =item eio_realpath (const char *path, int pri, eio_cb cb, void *data) |
|
|
406 | |
|
|
407 | Similar to the realpath libc function, but unlike that one, result is |
|
|
408 | C<-1> on failure and the length of the returned path in C<ptr2> (which is |
|
|
409 | not 0-terminated) - this is similar to readlink. |
|
|
410 | |
|
|
411 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
|
|
412 | |
|
|
413 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
|
|
414 | |
391 | =item eio_fstat (int fd, int pri, eio_cb cb, void *data) |
415 | =item eio_fstat (int fd, int pri, eio_cb cb, void *data) |
392 | |
416 | |
393 | Stats a file - if C<< req->result >> indicates success, then you can |
417 | Stats a file - if C<< req->result >> indicates success, then you can |
394 | access the C<struct stat>-like structure via C<< req->ptr2 >>: |
418 | access the C<struct stat>-like structure via C<< req->ptr2 >>: |
395 | |
419 | |
396 | EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; |
420 | EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; |
397 | |
421 | |
398 | =item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
422 | =item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) |
|
|
423 | |
|
|
424 | =item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) |
399 | |
425 | |
400 | Stats a filesystem - if C<< req->result >> indicates success, then you can |
426 | Stats a filesystem - if C<< req->result >> indicates success, then you can |
401 | access the C<struct statvfs>-like structure via C<< req->ptr2 >>: |
427 | access the C<struct statvfs>-like structure via C<< req->ptr2 >>: |
402 | |
428 | |
403 | EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; |
429 | EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; |
404 | |
430 | |
405 | =back |
431 | =back |
406 | |
432 | |
407 | =head3 READING DIRECTORIES |
433 | =head3 READING DIRECTORIES |
408 | |
434 | |
… | |
… | |
419 | (via the C<opendir>, C<readdir> and C<closedir> calls) and returns either |
445 | (via the C<opendir>, C<readdir> and C<closedir> calls) and returns either |
420 | the names or an array of C<struct eio_dirent>, depending on the C<flags> |
446 | the names or an array of C<struct eio_dirent>, depending on the C<flags> |
421 | argument. |
447 | argument. |
422 | |
448 | |
423 | The C<< req->result >> indicates either the number of files found, or |
449 | The C<< req->result >> indicates either the number of files found, or |
424 | C<-1> on error. On success, zero-terminated names can be found as C<< req->ptr2 >>, |
450 | C<-1> on error. On success, null-terminated names can be found as C<< req->ptr2 >>, |
425 | and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< |
451 | and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< |
426 | req->ptr1 >>. |
452 | req->ptr1 >>. |
427 | |
453 | |
428 | Here is an example that prints all the names: |
454 | Here is an example that prints all the names: |
429 | |
455 | |
… | |
… | |
448 | |
474 | |
449 | If this flag is specified, then, in addition to the names in C<ptr2>, |
475 | If this flag is specified, then, in addition to the names in C<ptr2>, |
450 | also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct |
476 | also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct |
451 | eio_dirent> looks like this: |
477 | eio_dirent> looks like this: |
452 | |
478 | |
453 | struct eio_dirent |
479 | struct eio_dirent |
454 | { |
480 | { |
455 | int nameofs; /* offset of null-terminated name string in (char *)req->ptr2 */ |
481 | int nameofs; /* offset of null-terminated name string in (char *)req->ptr2 */ |
456 | unsigned short namelen; /* size of filename without trailing 0 */ |
482 | unsigned short namelen; /* size of filename without trailing 0 */ |
457 | unsigned char type; /* one of EIO_DT_* */ |
483 | unsigned char type; /* one of EIO_DT_* */ |
458 | signed char score; /* internal use */ |
484 | signed char score; /* internal use */ |
459 | ino_t inode; /* the inode number, if available, otherwise unspecified */ |
485 | ino_t inode; /* the inode number, if available, otherwise unspecified */ |
460 | }; |
486 | }; |
461 | |
487 | |
462 | The only members you normally would access are C<nameofs>, which is the |
488 | The only members you normally would access are C<nameofs>, which is the |
463 | byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>. |
489 | byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>. |
464 | |
490 | |
465 | C<type> can be one of: |
491 | C<type> can be one of: |
… | |
… | |
561 | =item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) |
587 | =item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) |
562 | |
588 | |
563 | Calls C<sync_file_range>. If the syscall is missing, then this is the same |
589 | Calls C<sync_file_range>. If the syscall is missing, then this is the same |
564 | as calling C<fdatasync>. |
590 | as calling C<fdatasync>. |
565 | |
591 | |
|
|
592 | Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>, |
|
|
593 | C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>. |
|
|
594 | |
566 | =back |
595 | =back |
567 | |
596 | |
568 | =head3 LIBEIO-SPECIFIC REQUESTS |
597 | =head3 LIBEIO-SPECIFIC REQUESTS |
569 | |
598 | |
570 | These requests are specific to libeio and do not correspond to any OS call. |
599 | These requests are specific to libeio and do not correspond to any OS call. |
571 | |
600 | |
572 | =over 4 |
601 | =over 4 |
573 | |
602 | |
574 | =item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
603 | =item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
575 | |
604 | |
|
|
605 | Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given |
|
|
606 | memory area, page-wise, that is, it reads (or reads and writes back) the |
|
|
607 | first octet of every page that spans the memory area. |
|
|
608 | |
|
|
609 | This can be used to page in some mmapped file, or dirty some pages. Note |
|
|
610 | that dirtying is an unlocked read-write access, so races can ensue when |
|
|
611 | the some other thread modifies the data stored in that memory area. |
|
|
612 | |
576 | =item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) |
613 | =item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) |
577 | |
614 | |
578 | Executes a custom request, i.e., a user-specified callback. |
615 | Executes a custom request, i.e., a user-specified callback. |
579 | |
616 | |
580 | The callback gets the C<eio_req *> as parameter and is expected to read |
617 | The callback gets the C<eio_req *> as parameter and is expected to read |
581 | and modify any request-specific members. Specifically, it should set C<< |
618 | and modify any request-specific members. Specifically, it should set C<< |
… | |
… | |
601 | req->result = open (req->data, O_RDONLY); |
638 | req->result = open (req->data, O_RDONLY); |
602 | } |
639 | } |
603 | |
640 | |
604 | eio_custom (my_open, 0, my_open_done, "/etc/passwd"); |
641 | eio_custom (my_open, 0, my_open_done, "/etc/passwd"); |
605 | |
642 | |
606 | =item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) |
643 | =item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) |
607 | |
644 | |
608 | This is a a request that takes C<delay> seconds to execute, but otherwise |
645 | This is a a request that takes C<delay> seconds to execute, but otherwise |
609 | does nothing - it simply puts one of the worker threads to sleep for this |
646 | does nothing - it simply puts one of the worker threads to sleep for this |
610 | long. |
647 | long. |
611 | |
648 | |
612 | This request can be used to artificially increase load, e.g. for debugging |
649 | This request can be used to artificially increase load, e.g. for debugging |
613 | or benchmarking reasons. |
650 | or benchmarking reasons. |
614 | |
651 | |
615 | =item eio_nop (int pri, eio_cb cb, void *data) |
652 | =item eio_nop (int pri, eio_cb cb, void *data) |
616 | |
653 | |
617 | This request does nothing, except go through the whole request cycle. This |
654 | This request does nothing, except go through the whole request cycle. This |
618 | can be used to measure latency or in some cases to simplify code, but is |
655 | can be used to measure latency or in some cases to simplify code, but is |
619 | not really of much use. |
656 | not really of much use. |
620 | |
657 | |
621 | =back |
658 | =back |
622 | |
659 | |
623 | =head3 GROUPING AND LIMITING REQUESTS |
660 | =head3 GROUPING AND LIMITING REQUESTS |
624 | |
661 | |
|
|
662 | There is one more rather special request, C<eio_grp>. It is a very special |
|
|
663 | aio request: Instead of doing something, it is a container for other eio |
|
|
664 | requests. |
|
|
665 | |
|
|
666 | There are two primary use cases for this: a) bundle many requests into a |
|
|
667 | single, composite, request with a definite callback and the ability to |
|
|
668 | cancel the whole request with its subrequests and b) limiting the number |
|
|
669 | of "active" requests. |
|
|
670 | |
|
|
671 | Further below you will find more dicussion of these topics - first follows |
|
|
672 | the reference section detailing the request generator and other methods. |
|
|
673 | |
|
|
674 | =over 4 |
|
|
675 | |
|
|
676 | =item eio_req *grp = eio_grp (eio_cb cb, void *data) |
|
|
677 | |
|
|
678 | Creates, submits and returns a group request. |
|
|
679 | |
|
|
680 | =item eio_grp_add (eio_req *grp, eio_req *req) |
|
|
681 | |
|
|
682 | Adds a request to the request group. |
|
|
683 | |
|
|
684 | =item eio_grp_cancel (eio_req *grp) |
|
|
685 | |
|
|
686 | Cancels all requests I<in> the group, but I<not> the group request |
|
|
687 | itself. You can cancel the group request via a normal C<eio_cancel> call. |
|
|
688 | |
|
|
689 | |
|
|
690 | |
|
|
691 | =back |
|
|
692 | |
|
|
693 | |
|
|
694 | |
625 | #TODO |
695 | #TODO |
626 | |
696 | |
627 | /*****************************************************************************/ |
697 | /*****************************************************************************/ |
628 | /* groups */ |
698 | /* groups */ |
629 | |
699 | |
630 | eio_req *eio_grp (eio_cb cb, void *data); |
700 | eio_req *eio_grp (eio_cb cb, void *data); |
631 | void eio_grp_feed (eio_req *grp, void (*feed)(eio_req *req), int limit); |
701 | void eio_grp_feed (eio_req *grp, void (*feed)(eio_req *req), int limit); |
632 | void eio_grp_limit (eio_req *grp, int limit); |
702 | void eio_grp_limit (eio_req *grp, int limit); |
633 | void eio_grp_add (eio_req *grp, eio_req *req); |
|
|
634 | void eio_grp_cancel (eio_req *grp); /* cancels all sub requests but not the group */ |
703 | void eio_grp_cancel (eio_req *grp); /* cancels all sub requests but not the group */ |
635 | |
704 | |
636 | |
705 | |
637 | =back |
706 | =back |
638 | |
707 | |
… | |
… | |
645 | =head1 ANATOMY AND LIFETIME OF AN EIO REQUEST |
714 | =head1 ANATOMY AND LIFETIME OF AN EIO REQUEST |
646 | |
715 | |
647 | A request is represented by a structure of type C<eio_req>. To initialise |
716 | A request is represented by a structure of type C<eio_req>. To initialise |
648 | it, clear it to all zero bytes: |
717 | it, clear it to all zero bytes: |
649 | |
718 | |
650 | eio_req req; |
719 | eio_req req; |
651 | |
720 | |
652 | memset (&req, 0, sizeof (req)); |
721 | memset (&req, 0, sizeof (req)); |
653 | |
722 | |
654 | A more common way to initialise a new C<eio_req> is to use C<calloc>: |
723 | A more common way to initialise a new C<eio_req> is to use C<calloc>: |
655 | |
724 | |
656 | eio_req *req = calloc (1, sizeof (*req)); |
725 | eio_req *req = calloc (1, sizeof (*req)); |
657 | |
726 | |
658 | In either case, libeio neither allocates, initialises or frees the |
727 | In either case, libeio neither allocates, initialises or frees the |
659 | C<eio_req> structure for you - it merely uses it. |
728 | C<eio_req> structure for you - it merely uses it. |
660 | |
729 | |
661 | zero |
730 | zero |
662 | |
731 | |
663 | #TODO |
732 | #TODO |
|
|
733 | |
|
|
734 | =head2 CONFIGURATION |
|
|
735 | |
|
|
736 | The functions in this section can sometimes be useful, but the default |
|
|
737 | configuration will do in most case, so you should skip this section on |
|
|
738 | first reading. |
|
|
739 | |
|
|
740 | =over 4 |
|
|
741 | |
|
|
742 | =item eio_set_max_poll_time (eio_tstamp nseconds) |
|
|
743 | |
|
|
744 | This causes C<eio_poll ()> to return after it has detected that it was |
|
|
745 | running for C<nsecond> seconds or longer (this number can be fractional). |
|
|
746 | |
|
|
747 | This can be used to limit the amount of time spent handling eio requests, |
|
|
748 | for example, in interactive programs, you might want to limit this time to |
|
|
749 | C<0.01> seconds or so. |
|
|
750 | |
|
|
751 | Note that: |
|
|
752 | |
|
|
753 | a) libeio doesn't know how long your request callbacks take, so the time |
|
|
754 | spent in C<eio_poll> is up to one callback invocation longer then this |
|
|
755 | interval. |
|
|
756 | |
|
|
757 | b) this is implemented by calling C<gettimeofday> after each request, |
|
|
758 | which can be costly. |
|
|
759 | |
|
|
760 | c) at least one request will be handled. |
|
|
761 | |
|
|
762 | =item eio_set_max_poll_reqs (unsigned int nreqs) |
|
|
763 | |
|
|
764 | When C<nreqs> is non-zero, then C<eio_poll> will not handle more than |
|
|
765 | C<nreqs> requests per invocation. This is a less costly way to limit the |
|
|
766 | amount of work done by C<eio_poll> then setting a time limit. |
|
|
767 | |
|
|
768 | If you know your callbacks are generally fast, you could use this to |
|
|
769 | encourage interactiveness in your programs by setting it to C<10>, C<100> |
|
|
770 | or even C<1000>. |
|
|
771 | |
|
|
772 | =item eio_set_min_parallel (unsigned int nthreads) |
|
|
773 | |
|
|
774 | Make sure libeio can handle at least this many requests in parallel. It |
|
|
775 | might be able handle more. |
|
|
776 | |
|
|
777 | =item eio_set_max_parallel (unsigned int nthreads) |
|
|
778 | |
|
|
779 | Set the maximum number of threads that libeio will spawn. |
|
|
780 | |
|
|
781 | =item eio_set_max_idle (unsigned int nthreads) |
|
|
782 | |
|
|
783 | Libeio uses threads internally to handle most requests, and will start and stop threads on demand. |
|
|
784 | |
|
|
785 | This call can be used to limit the number of idle threads (threads without |
|
|
786 | work to do): libeio will keep some threads idle in preparation for more |
|
|
787 | requests, but never longer than C<nthreads> threads. |
|
|
788 | |
|
|
789 | In addition to this, libeio will also stop threads when they are idle for |
|
|
790 | a few seconds, regardless of this setting. |
|
|
791 | |
|
|
792 | =item unsigned int eio_nthreads () |
|
|
793 | |
|
|
794 | Return the number of worker threads currently running. |
|
|
795 | |
|
|
796 | =item unsigned int eio_nreqs () |
|
|
797 | |
|
|
798 | Return the number of requests currently handled by libeio. This is the |
|
|
799 | total number of requests that have been submitted to libeio, but not yet |
|
|
800 | destroyed. |
|
|
801 | |
|
|
802 | =item unsigned int eio_nready () |
|
|
803 | |
|
|
804 | Returns the number of ready requests, i.e. requests that have been |
|
|
805 | submitted but have not yet entered the execution phase. |
|
|
806 | |
|
|
807 | =item unsigned int eio_npending () |
|
|
808 | |
|
|
809 | Returns the number of pending requests, i.e. requests that have been |
|
|
810 | executed and have results, but have not been finished yet by a call to |
|
|
811 | C<eio_poll>). |
|
|
812 | |
|
|
813 | =back |
664 | |
814 | |
665 | =head1 EMBEDDING |
815 | =head1 EMBEDDING |
666 | |
816 | |
667 | Libeio can be embedded directly into programs. This functionality is not |
817 | Libeio can be embedded directly into programs. This functionality is not |
668 | documented and not (yet) officially supported. |
818 | documented and not (yet) officially supported. |