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239 | |
239 | |
240 | IO::AIO::poll_wait, IO::AIO::poll_cb |
240 | IO::AIO::poll_wait, IO::AIO::poll_cb |
241 | if IO::AIO::nreqs; |
241 | if IO::AIO::nreqs; |
242 | |
242 | |
243 | IO::AIO::min_parallel $nthreads |
243 | IO::AIO::min_parallel $nthreads |
244 | Set the minimum number of AIO threads to $nthreads. The default is |
244 | Set the minimum number of AIO threads to $nthreads. The current |
245 | 1, which means a single asynchronous operation can be done at one |
245 | default is 4, which means four asynchronous operations can be done |
246 | time (the number of outstanding operations, however, is unlimited). |
246 | at one time (the number of outstanding operations, however, is |
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247 | unlimited). |
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248 | |
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249 | IO::AIO starts threads only on demand, when an AIO request is queued |
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250 | and no free thread exists. |
247 | |
251 | |
248 | It is recommended to keep the number of threads low, as some Linux |
252 | It is recommended to keep the number of threads low, as some Linux |
249 | kernel versions will scale negatively with the number of threads |
253 | kernel versions will scale negatively with the number of threads |
250 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
254 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
251 | versions, 4-32 threads should be fine. |
255 | versions, 4-32 threads should be fine. |
252 | |
256 | |
253 | Under normal circumstances you don't need to call this function, as |
257 | Under most circumstances you don't need to call this function, as |
254 | this module automatically starts some threads (the exact number |
258 | the module selects a default that is suitable for low to moderate |
255 | might change, and is currently 4). |
259 | load. |
256 | |
260 | |
257 | IO::AIO::max_parallel $nthreads |
261 | IO::AIO::max_parallel $nthreads |
258 | Sets the maximum number of AIO threads to $nthreads. If more than |
262 | Sets the maximum number of AIO threads to $nthreads. If more than |
259 | the specified number of threads are currently running, kill them. |
263 | the specified number of threads are currently running, this function |
260 | This function blocks until the limit is reached. |
264 | kills them. This function blocks until the limit is reached. |
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265 | |
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266 | While $nthreads are zero, aio requests get queued but not executed |
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267 | until the number of threads has been increased again. |
261 | |
268 | |
262 | This module automatically runs "max_parallel 0" at program end, to |
269 | This module automatically runs "max_parallel 0" at program end, to |
263 | ensure that all threads are killed and that there are no outstanding |
270 | ensure that all threads are killed and that there are no outstanding |
264 | requests. |
271 | requests. |
265 | |
272 | |
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269 | Sets the maximum number of outstanding requests to $nreqs. If you |
276 | Sets the maximum number of outstanding requests to $nreqs. If you |
270 | try to queue up more than this number of requests, the caller will |
277 | try to queue up more than this number of requests, the caller will |
271 | block until some requests have been handled. |
278 | block until some requests have been handled. |
272 | |
279 | |
273 | The default is very large, so normally there is no practical limit. |
280 | The default is very large, so normally there is no practical limit. |
274 | If you queue up many requests in a loop it it often improves speed |
281 | If you queue up many requests in a loop it often improves speed if |
275 | if you set this to a relatively low number, such as 100. |
282 | you set this to a relatively low number, such as 100. |
276 | |
283 | |
277 | Under normal circumstances you don't need to call this function. |
284 | Under normal circumstances you don't need to call this function. |
278 | |
285 | |
279 | FORK BEHAVIOUR |
286 | FORK BEHAVIOUR |
280 | Before the fork IO::AIO enters a quiescent state where no requests can |
287 | Before the fork, IO::AIO enters a quiescent state where no requests can |
281 | be added in other threads and no results will be processed. After the |
288 | be added in other threads and no results will be processed. After the |
282 | fork the parent simply leaves the quiescent state and continues |
289 | fork the parent simply leaves the quiescent state and continues |
283 | request/result processing, while the child clears the request/result |
290 | request/result processing, while the child clears the request/result |
284 | queue and starts the same number of threads as were in use by the |
291 | queue (so the requests started before the fork will only be handled in |
285 | parent. |
292 | the parent). Threats will be started on demand until the limit ste in |
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293 | the parent process has been reached again. |
286 | |
294 | |
287 | SEE ALSO |
295 | SEE ALSO |
288 | Coro, Linux::AIO. |
296 | Coro, Linux::AIO. |
289 | |
297 | |
290 | AUTHOR |
298 | AUTHOR |