reqpool.cpp@ 39517

Last change on this file since 39517 was 39517, checked in by vboxsync, 13 years ago
Some request thread pool musings.
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1	/* $Id: reqpool.cpp 39517 2011-12-02 15:58:27Z vboxsync $ */
2	/** @file
3	* IPRT - Request Pool.
4	*/
5
6	/*
7	* Copyright (C) 2006-2011 Oracle Corporation
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.215389.xyz. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*
17	* The contents of this file may alternatively be used under the terms
18	* of the Common Development and Distribution License Version 1.0
19	* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
20	* VirtualBox OSE distribution, in which case the provisions of the
21	* CDDL are applicable instead of those of the GPL.
22	*
23	* You may elect to license modified versions of this file under the
24	* terms and conditions of either the GPL or the CDDL or both.
25	*/
26
27
28	/*******************************************************************************
29	* Header Files *
30	*******************************************************************************/
31	#include <iprt/req.h>
32	#include "internal/iprt.h"
33
34	#include <iprt/assert.h>
35	#include <iprt/asm.h>
36	#include <iprt/critsect.h>
37	#include <iprt/list.h>
38	#include <iprt/log.h>
39	#include <iprt/mem.h>
40	#include <iprt/string.h>
41	#include <iprt/time.h>
42	#include <iprt/semaphore.h>
43	#include <iprt/thread.h>
44
45	#include "internal/req.h"
46	#include "internal/magics.h"
47
48
49	/*******************************************************************************
50	* Structures and Typedefs *
51	*******************************************************************************/
52	typedef struct RTREQPOOLTHREAD
53	{
54	/** Node in the RTREQPOOLINT::IdleThreads list. */
55	RTLISTNODE IdleNode;
56	/** Node in the RTREQPOOLINT::WorkerThreads list. */
57	RTLISTNODE ListNode;
58
59	/** The submit timestamp of the pending request. */
60	uint64_t uPendingNanoTs;
61	/** The submit timestamp of the request processing. */
62	uint64_t uProcessingNanoTs;
63	/** When this CPU went idle the last time. */
64	uint64_t uIdleNanoTs;
65	/** The number of requests processed by this thread. */
66	uint64_t cReqProcessed;
67	/** Total time the requests processed by this thread took to process. */
68	uint64_t cNsTotalReqProcessing;
69	/** Total time the requests processed by this thread had to wait in
70	* the queue before being scheduled. */
71	uint64_t cNsTotalReqQueued;
72	/** The CPU this was scheduled last time we checked. */
73	RTCPUID idLastCpu;
74
75	/** The submitter will put an incoming request here when scheduling an idle
76	* thread. */
77	PRTREQINT volatile pTodoReq;
78	/** The request the thread is currently processing. */
79	PRTREQINT volatile pPendingReq;
80
81	/** The thread handle. */
82	RTTHREAD hThread;
83	/** Nano seconds timestamp representing the birth time of the thread. */
84	uint64_t uBirthNanoTs;
85	/** Pointer to the request thread pool instance the thread is associated
86	* with. */
87	struct RTREQPOOLINT *pPool;
88	} RTREQPOOLTHREAD;
89	/** Pointer to a worker thread. */
90	typedef RTREQPOOLTHREAD *PRTREQPOOLTHREAD;
91
92	/**
93	* Request thread pool instance data.
94	*/
95	typedef struct RTREQPOOLINT
96	{
97	/** Magic value (RTREQPOOL_MAGIC). */
98	uint32_t u32Magic;
99
100	/** The worker thread type. */
101	RTTHREADTYPE enmThreadType;
102	/** The current number of worker threads. */
103	uint32_t cCurThreads;
104	/** The maximum number of worker threads. */
105	uint32_t cMaxThreads;
106	/** The number of threads which should be spawned before throttling kicks
107	* in. */
108	uint32_t cThreadsThreshold;
109	/** The minimum number of worker threads. */
110	uint32_t cMinThreads;
111	/** The number of milliseconds a thread needs to be idle before it is
112	* considered for retirement. */
113	uint32_t cMsMinIdle;
114	/** The max number of milliseconds to push back a submitter before creating
115	* a new worker thread once the threshold has been reached. */
116	uint32_t cMsMaxPushBack;
117	/** The minimum number of milliseconds to push back a submitter before
118	* creating a new worker thread once the threshold has been reached. */
119	uint32_t cMsMinPushBack;
120	/** The current submitter push back in milliseconds.
121	* This is recalculated when worker threads come and go. */
122	uint32_t cMsCurPushBack;
123
124	/** Statistics: The total number of threads created. */
125	uint32_t cThreadsCreated;
126	/** Statistics: The timestamp when the last thread was created. */
127	uint64_t uLastThreadCreateNanoTs;
128	/** Linked list of worker threads. */
129	RTLISTANCHOR WorkerThreads;
130
131	/** Event semaphore that submitters block on when pushing back . */
132	RTSEMEVENT hPushBackEvt;
133
134	/** Critical section serializing access to members of this structure. */
135	RTCRITSECT CritSect;
136
137	/** Destruction indicator. The worker threads checks in their loop. */
138	bool volatile fDestructing;
139
140	/** Reference counter. */
141	uint32_t volatile cRefs;
142	/** Number of threads pushing back. */
143	uint32_t volatile cPushingBack;
144	/** The number of idle thread or threads in the process of becoming
145	* idle. This is increased before the to-be-idle thread tries to enter
146	* the critical section and add itself to the list. */
147	uint32_t volatile cIdleThreads;
148	/** Linked list of idle threads. */
149	RTLISTANCHOR IdleThreads;
150
151	/** Head of the request FIFO. */
152	PRTREQINT pPendingRequests;
153	/** Where to insert the next request. */
154	PRTREQINT *ppPendingRequests;
155
156	} RTREQPOOLINT;
157	/** Pointer to a request thread pool instance. */
158	typedef RTREQPOOLINT *PRTREQPOOLINT;
159
160
161	static void rtReqPoolRecalcPushBack(PRTREQPOOLINT pPool)
162	{
163	uint32_t const cMsRange = pPool->cMsMaxPushBack - pPool->cMsMinPushBack;
164	uint32_t const cSteps = pPool->cMaxThreads - pPool->cThreadsThreshold;
165	uint32_t const iStep = pPool->cCurThreads - pPool->cThreadsThreshold;
166
167	uint32_t cMsCurPushBack;
168	if ((cMsRange >> 2) >= cSteps)
169	cMsCurPushBack = cMsRange / cSteps * iStep;
170	else
171	cMsCurPushBack = (uint32_t)( (uint64_t)cMsRange * RT_NS_1MS / cSteps * iStep / RT_NS_1MS );
172	cMsCurPushBack += pPool->cMsMinPushBack;
173
174	pPool->cMsCurPushBack = cMsCurPushBack;
175	}
176
177
178
179	static void rtReqPoolThreadProcessRequest(PRTREQPOOLTHREAD pThread, PRTREQINT pReq)
180	{
181	/*
182	* Update thread state.
183	*/
184	pThread->uProcessingNanoTs = RTTimeNanoTS();
185	pThread->uPendingNanoTs = pReq->uSubmitNanoTs;
186	pThread->pPendingReq = pReq;
187	Assert(pReq->u32Magic == RTREQ_MAGIC);
188
189	/*
190	* Do the actual processing.
191	*/
192	/** @todo */
193
194	/*
195	* Update thread statistics and state.
196	*/
197	uint64_t const uNsTsEnd = RTTimeNanoTS();
198	pThread->cNsTotalReqProcessing += uNsTsEnd - pThread->uProcessingNanoTs;
199	pThread->cNsTotalReqQueued += uNsTsEnd - pThread->uPendingNanoTs;
200	pThread->cReqProcessed++;
201	}
202
203
204
205	static DECLCALLBACK(int) rtReqPoolThreadProc(RTTHREAD hThreadSelf, void *pvArg)
206	{
207	PRTREQPOOLTHREAD pThread = (PRTREQPOOLTHREAD)pvArg;
208	PRTREQPOOLINT pPool = pThread->pPool;
209
210	/*
211	* The work loop.
212	*/
213	uint64_t cPrevReqProcessed = 0;
214	while (pPool->fDestructing)
215	{
216	/*
217	* Pending work?
218	*/
219	PRTREQINT pReq = ASMAtomicXchgPtrT(&pThread->pTodoReq, NULL, PRTREQINT);
220	if (pReq)
221	rtReqPoolThreadProcessRequest(pThread, pReq);
222	else
223	{
224	ASMAtomicIncU32(&pPool->cIdleThreads);
225	RTCritSectEnter(&pPool->CritSect);
226
227	/* Recheck the todo request pointer after entering the critsect. */
228	pReq = ASMAtomicXchgPtrT(&pThread->pTodoReq, NULL, PRTREQINT);
229	if (!pReq)
230	{
231	/* Any pending requests in the queue? */
232	pReq = pPool->pPendingRequests;
233	if (pReq)
234	{
235	pPool->pPendingRequests = pReq->pNext;
236	if (pReq->pNext == NULL)
237	pPool->ppPendingRequests = &pPool->pPendingRequests;
238	}
239	}
240
241	if (pReq)
242	{
243	/*
244	* Un-idle ourselves and process the request.
245	*/
246	if (!RTListIsEmpty(&pThread->IdleNode))
247	{
248	RTListNodeRemove(&pThread->IdleNode);
249	RTListInit(&pThread->IdleNode);
250	}
251	ASMAtomicDecU32(&pPool->cIdleThreads);
252	RTCritSectLeave(&pPool->CritSect);
253
254	rtReqPoolThreadProcessRequest(pThread, pReq);
255	}
256	else
257	{
258	/*
259	* Nothing to do, go idle.
260	*/
261	if (cPrevReqProcessed != pThread->cReqProcessed)
262	{
263	pThread->cReqProcessed = cPrevReqProcessed;
264	pThread->uIdleNanoTs = RTTimeNanoTS();
265	}
266
267	if (RTListIsEmpty(&pThread->IdleNode))
268	RTListPrepend(&pPool->IdleThreads, &pThread->IdleNode);
269	RTThreadUserReset(hThreadSelf);
270
271	RTCritSectLeave(&pPool->CritSect);
272
273	RTThreadUserWait(hThreadSelf, 0);
274
275
276
277	}
278	}
279	}
280
281	/*
282	* Clean up on the way out.
283	*/
284	RTCritSectEnter(&pPool->CritSect);
285
286	/** @todo .... */
287
288	rtReqPoolRecalcPushBack(pPool);
289
290	RTCritSectLeave(&pPool->CritSect);
291
292	return VINF_SUCCESS;
293	}
294
295
296	DECLHIDDEN(int) rtReqPoolSubmit(PRTREQPOOLINT pPool, PRTREQINT pReq)
297	{
298	/*
299	* Prepare the request.
300	*/
301	pReq->uSubmitNanoTs = RTTimeNanoTS();
302
303
304	RTCritSectEnter(&pPool->CritSect);
305
306	/*
307	* Try schedule the request to any currently idle thread.
308	*/
309	PRTREQPOOLTHREAD pThread = RTListGetFirst(&pPool->IdleThreads, RTREQPOOLTHREAD, IdleNode);
310	if (pThread)
311	{
312	/** @todo CPU affinity... */
313	ASMAtomicWritePtr(&pThread->pTodoReq, pReq);
314
315	RTListNodeRemove(&pThread->IdleNode);
316	RTListInit(&pThread->IdleNode);
317	ASMAtomicDecU32(&pPool->cIdleThreads);
318
319	RTThreadUserSignal(pThread->hThread);
320
321	RTCritSectLeave(&pPool->CritSect);
322	return VINF_SUCCESS;
323	}
324	Assert(RTListIsEmpty(&pPool->IdleThreads));
325
326	/*
327	* Put the request in the pending queue.
328	*/
329	pReq->pNext = NULL;
330	*pPool->ppPendingRequests = pReq;
331	pPool->ppPendingRequests = (PRTREQINT*)&pReq->pNext;
332
333	/*
334	* If there is an incoming worker thread already or we've reached the
335	* maximum number of worker threads, we're done.
336	*/
337	if ( pPool->cIdleThreads > 0
338	\|\| pPool->cCurThreads >= pPool->cMaxThreads)
339	{
340	RTCritSectLeave(&pPool->CritSect);
341	return VINF_SUCCESS;
342	}
343
344	/*
345	* Push back before creating a new worker thread.
346	*/
347	if ( pPool->cCurThreads > pPool->cThreadsThreshold
348	&& (RTTimeNanoTS() - pReq->uSubmitNanoTs) / RT_NS_1MS >= pPool->cMsCurPushBack )
349	{
350	uint32_t const cMsTimeout = pPool->cMsCurPushBack;
351	pPool->cPushingBack++;
352	RTCritSectLeave(&pPool->CritSect);
353
354	/** @todo this is everything but perfect... it makes wake up order
355	* assumptions. A better solution would be having a lazily
356	* allocated push back event on each request. */
357	int rc = RTSemEventWait(pPool->hPushBackEvt, cMsTimeout);
358
359	RTCritSectEnter(&pPool->CritSect);
360	pPool->cPushingBack--;
361	}
362
363	/*
364	* Create a new thread for processing the request, or should we wait?
365	*/
366	pThread = (PRTREQPOOLTHREAD)RTMemAllocZ(sizeof(RTREQPOOLTHREAD));
367	if (pThread)
368	{
369	pThread->uBirthNanoTs = RTTimeNanoTS();
370	pThread->pPool = pPool;
371	pThread->idLastCpu = NIL_RTCPUID;
372	pThread->hThread = NIL_RTTHREAD;
373	RTListInit(&pThread->IdleNode);
374	RTListAppend(&pPool->WorkerThreads, &pThread->ListNode);
375	pPool->cCurThreads++;
376	pPool->cThreadsCreated++;
377
378	static uint32_t s_idThread = 0;
379	int rc = RTThreadCreateF(&pThread->hThread, rtReqPoolThreadProc, pThread, 0 /default stack size/,
380	pPool->enmThreadType, RTTHREADFLAGS_WAITABLE, "REQPT%02u", ++s_idThread);
381	if (RT_SUCCESS(rc))
382	pPool->uLastThreadCreateNanoTs = pThread->uBirthNanoTs;
383	else
384	{
385	pPool->cCurThreads--;
386	RTListNodeRemove(&pThread->ListNode);
387	RTMemFree(pThread);
388	}
389	}
390	RTCritSectLeave(&pPool->CritSect);
391
392	return VINF_SUCCESS;
393	}
394

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source: vbox/trunk/src/VBox/Runtime/common/misc/reqpool.cpp@ 39517

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