memcache.cpp@ 26417

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1	/* $Id: memcache.cpp 26417 2010-02-10 17:07:21Z vboxsync $ */
2	/** @file
3	* IPRT - Memory Object Allocation Cache.
4	*/
5
6	/*
7	* Copyright (C) 2006-2010 Sun Microsystems, Inc.
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.virtualbox.org. 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	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
27	* Clara, CA 95054 USA or visit http://www.sun.com if you need
28	* additional information or have any questions.
29	*/
30
31
32	/*******************************************************************************
33	* Header Files *
34	*******************************************************************************/
35	#include <iprt/memcache.h>
36	#include "internal/iprt.h"
37
38	#include <iprt/assert.h>
39	#include <iprt/asm.h>
40	#include <iprt/critsect.h>
41	#include <iprt/err.h>
42	#include <iprt/mem.h>
43	#include <iprt/param.h>
44
45	#include "internal/magics.h"
46
47
48	/*******************************************************************************
49	* Structures and Typedefs *
50	*******************************************************************************/
51	/** Pointer to a cache instance. */
52	typedef struct RTMEMCACHEINT *PRTMEMCACHEINT;
53	/** Pointer to a cache page. */
54	typedef struct RTMEMCACHEPAGE *PRTMEMCACHEPAGE;
55
56
57	/**
58	* A cache page.
59	*
60	* This is a page of memory that we split up in to a bunch object sized chunks
61	* and hand out to the cache users. The bitmap is updated in an atomic fashion
62	* so that we don't have to take any locks when freeing or allocating memory.
63	*/
64	typedef struct RTMEMCACHEPAGE
65	{
66	/** Pointer to the cache owning this page.
67	* This is used for validation purposes only. */
68	PRTMEMCACHEINT pCache;
69	/** Pointer to the next page.
70	* This is marked as volatile since we'll be adding new entries to the list
71	* without taking any locks. */
72	PRTMEMCACHEPAGE volatile pNext;
73	/** The number of free objects. */
74	int32_t volatile cFree;
75	/** The number of objects on this page. */
76	uint32_t cObjects;
77	/** Bitmap tracking allocated blocks. */
78	void volatile *pbmAlloc;
79	/** Bitmap tracking which blocks that has been thru the constructor. */
80	void volatile *pbmCtor;
81	/** Pointer to the object array.. */
82	uint8_t *pbObjects;
83	} RTMEMCACHEPAGE;
84
85
86	/**
87	* Memory object cache instance.
88	*/
89	typedef struct RTMEMCACHEINT
90	{
91	/** Magic value (RTMEMCACHE_MAGIC). */
92	uint32_t u32Magic;
93	/** The object size. */
94	uint32_t cbObject;
95	/** Object alignment. */
96	uint32_t cbAlignment;
97	/** The per page object count. */
98	uint32_t cPerPage;
99	/** Number of bits in the bitmap.
100	* @remarks This is higher or equal to cPerPage and it is aligned such that
101	* the search operation will be most efficient on x86/AMD64. */
102	uint32_t cBits;
103	/** The maximum number of objects. */
104	uint32_t cMax;
105	/** The total object count. */
106	uint32_t volatile cTotal;
107	/** The number of free objects. */
108	int32_t volatile cFree;
109	/** Head of the page list. */
110	PRTMEMCACHEPAGE pPageHead;
111	/** This may point to a page with free entries. */
112	PRTMEMCACHEPAGE volatile pPageHint;
113	/** Constructor callback. */
114	PFNMEMCACHECTOR pfnCtor;
115	/** Destructor callback. */
116	PFNMEMCACHEDTOR pfnDtor;
117	/** Callback argument. */
118	void *pvUser;
119	/** Critical section serializing page allocation and similar. */
120	RTCRITSECT CritSect;
121	} RTMEMCACHEINT;
122
123
124
125	RTDECL(int) RTMemCacheCreate(PRTMEMCACHE phMemCache, size_t cbObject, size_t cbAlignment, uint32_t cMaxObjects,
126	PFNMEMCACHECTOR pfnCtor, PFNMEMCACHEDTOR pfnDtor, void *pvUser)
127	{
128	AssertPtr(phMemCache);
129	AssertPtrNull(pfnCtor);
130	AssertPtrNull(pfnDtor);
131	AssertReturn(cbObject > 0, VERR_INVALID_PARAMETER);
132	AssertReturn(cbObject <= PAGE_SIZE / 8, VERR_INVALID_PARAMETER);
133
134	if (cbAlignment == 0)
135	{
136	cbAlignment = UINT32_C(1) << ASMBitLastSetU32((uint32_t)cbObject);
137	if (cbAlignment > 64)
138	cbAlignment = 64;
139	}
140	else
141	{
142	AssertReturn(!((cbAlignment - 1) & cbAlignment), VERR_NOT_POWER_OF_TWO);
143	AssertReturn(cbAlignment <= 64, VERR_OUT_OF_RANGE);
144	}
145
146	/*
147	* Allocate and initialize the instance memory.
148	*/
149	RTMEMCACHEINT pThis = (RTMEMCACHEINT )RTMemAlloc(sizeof(*pThis));
150	if (!pThis)
151	return VERR_NO_MEMORY;
152	int rc = RTCritSectInit(&pThis->CritSect);
153	if (RT_FAILURE(rc))
154	{
155	RTMemFree(pThis);
156	return rc;
157	}
158
159	pThis->u32Magic = RTMEMCACHE_MAGIC;
160	pThis->cbObject = RT_ALIGN_Z(cbObject, cbAlignment);
161	pThis->cbAlignment = cbAlignment;
162	pThis->cPerPage = (PAGE_SIZE - RT_ALIGN_Z(sizeof(RTMEMCACHEPAGE), cbAlignment)) / pThis->cbObject;
163	while ( RT_ALIGN_Z(sizeof(RTMEMCACHEPAGE), cbAlignment)
164	+ pThis->cPerPage * pThis->cbObject
165	+ RT_ALIGN(pThis->cPerPage, 32) * 2
166	> PAGE_SIZE)
167	pThis->cPerPage--;
168	pThis->cBits = RT_ALIGN(pThis->cPerPage, 32);
169	pThis->cMax = cMaxObjects;
170	pThis->cTotal = 0;
171	pThis->cFree = 0;
172	pThis->pPageHead = NULL;
173	pThis->pPageHint = NULL;
174	pThis->pfnCtor = pfnCtor;
175	pThis->pfnDtor = pfnDtor;
176	pThis->pvUser = pvUser;
177
178	*phMemCache = pThis;
179	return VINF_SUCCESS;
180	}
181
182
183	RTDECL(int) RTMemCacheDestroy(RTMEMCACHE hMemCache)
184	{
185	RTMEMCACHEINT *pThis = hMemCache;
186	if (!pThis)
187	return VINF_SUCCESS;
188	AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
189	AssertReturn(pThis->u32Magic == RTMEMCACHE_MAGIC, VERR_INVALID_HANDLE);
190	AssertMsg((uint32_t)pThis->cFree == pThis->cTotal, ("cFree=%u cTotal=%u\n", pThis->cFree, pThis->cTotal));
191
192	/*
193	* Destroy it.
194	*/
195	AssertReturn(ASMAtomicCmpXchgU32(&pThis->u32Magic, RTMEMCACHE_MAGIC_DEAD, RTMEMCACHE_MAGIC), VERR_INVALID_HANDLE);
196	RTCritSectDelete(&pThis->CritSect);
197
198	while (pThis->pPageHead)
199	{
200	PRTMEMCACHEPAGE pPage = pThis->pPageHead;
201	pThis->pPageHead = pPage->pNext;
202	pPage->cFree = 0;
203
204	if (pThis->pfnDtor)
205	{
206	uint32_t iObj = pPage->cObjects;
207	while (iObj-- > 0)
208	if (ASMBitTestAndClear(pPage->pbmCtor, iObj))
209	pThis->pfnDtor(hMemCache, (uint8_t )pPage->pbObjects + iObj pThis->cPerPage, pThis->pvUser);
210	}
211
212	RTMemPageFree(pPage);
213	}
214
215	RTMemFree(pThis);
216	return VINF_SUCCESS;
217	}
218
219
220	/**
221	* Grows the cache.
222	*
223	* @returns IPRT status code.
224	* @param pThis The memory cache instance.
225	*/
226	static int rtMemCacheGrow(RTMEMCACHEINT *pThis)
227	{
228	/*
229	* Enter the critical section here to avoid allocation races leading to
230	* wasted memory (++) and make it easier to link in the new page.
231	*/
232	RTCritSectEnter(&pThis->CritSect);
233	int rc = VINF_SUCCESS;
234	if (pThis->cFree < 0)
235	{
236	/*
237	* Allocate and initialize the new page.
238	*/
239	PRTMEMCACHEPAGE pPage = (PRTMEMCACHEPAGE)RTMemPageAlloc(PAGE_SIZE);
240	if (!pPage)
241	{
242	uint32_t cObjects = pThis->cPerPage;
243	if (pThis->cTotal + cObjects > pThis->cMax)
244	cObjects = pThis->cTotal - pThis->cMax;
245
246	ASMMemZeroPage(pPage);
247	pPage->pCache = pThis;
248	pPage->pNext = NULL;
249	pPage->cFree = cObjects;
250	pPage->pbmAlloc = (pThis + 1);
251	pPage->pbmCtor = (uint8_t *)pPage->pbmAlloc + pThis->cBits / 8;
252	pPage->pbObjects = (uint8_t *)pPage->pbmCtor + pThis->cBits / 8;
253	pPage->pbObjects = RT_ALIGN_PT(pPage->pbObjects, pThis->cbAlignment, uint8_t *);
254
255	/* Mark the bitmap padding and any unused objects as allocated. */
256	for (uint32_t iBit = cObjects; iBit < pThis->cBits; iBit++)
257	ASMBitSet(pPage->pbmAlloc, iBit);
258
259	/* Make it the hint. */
260	ASMAtomicWritePtr((void * volatile *)&pThis->pPageHint, pPage);
261
262	/* Link the page. */
263	PRTMEMCACHEPAGE pPrevPage = pThis->pPageHead;
264	if (!pPrevPage)
265	ASMAtomicWritePtr((void * volatile *)&pThis->pPageHead, pPage);
266	else
267	{
268	while (pPrevPage->pNext)
269	pPrevPage = pPrevPage->pNext;
270	ASMAtomicWritePtr((void * volatile *)&pPrevPage->pNext, pPage);
271	}
272
273	/* Add it to the page counts. */
274	ASMAtomicAddS32(&pThis->cFree, cObjects);
275	ASMAtomicAddU32(&pThis->cTotal, cObjects);
276	}
277	else
278	rc = VERR_NO_MEMORY;
279	}
280	RTCritSectLeave(&pThis->CritSect);
281	return rc;
282	}
283
284
285	/**
286	* Grabs a an object in a page.
287	* @returns New cFree value on success (0 or higher), -1 on failure.
288	* @param pPage Pointer to the page.
289	*/
290	DECL_FORCE_INLINE(int32_t) rtMemCacheGrabObj(PRTMEMCACHEPAGE pPage)
291	{
292	int32_t cFreeNew = ASMAtomicDecS32(&pPage->cFree);
293	if (cFreeNew < 0)
294	{
295	ASMAtomicIncS32(&pPage->cFree);
296	return -1;
297	}
298	return cFreeNew;
299	}
300
301
302	RTDECL(int) RTMemCacheAllocEx(RTMEMCACHE hMemCache, void **ppvObj)
303	{
304	RTMEMCACHEINT *pThis = hMemCache;
305	AssertPtrReturn(pThis, VERR_INVALID_PARAMETER);
306	AssertReturn(pThis->u32Magic == RTMEMCACHE_MAGIC, NULL);
307
308	/*
309	* Try grab a free object at the cache level.
310	*/
311	int32_t cNewFree = ASMAtomicDecS32(&pThis->cFree);
312	if (cNewFree < 0)
313	{
314	uint32_t cTotal = ASMAtomicUoReadU32(&pThis->cTotal);
315	if ( (uint32_t)(cTotal + -cNewFree) > pThis->cMax
316	\|\| (uint32_t)(cTotal + -cNewFree) <= cTotal)
317	{
318	ASMAtomicIncS32(&pThis->cFree);
319	return VERR_CACHE_EMPTY;
320	}
321
322	int rc = rtMemCacheGrow(pThis);
323	if (RT_FAILURE(rc))
324	{
325	ASMAtomicIncS32(&pThis->cFree);
326	return rc;
327	}
328	}
329
330	/*
331	* Grab a free object at the page level.
332	*/
333	PRTMEMCACHEPAGE pPage = (PRTMEMCACHEPAGE)ASMAtomicReadPtr((void * volatile *)&pThis->pPageHint);
334	int32_t iObj = pPage ? rtMemCacheGrabObj(pPage) : -1;
335	if (iObj < 0)
336	{
337	for (unsigned cLoops = 0; ; cLoops++)
338	{
339	for (pPage = pThis->pPageHead; pPage; pPage = pPage->pNext)
340	{
341	iObj = rtMemCacheGrabObj(pPage);
342	if (iObj >= 0)
343	{
344	if (iObj > 0)
345	ASMAtomicWritePtr((void * volatile *)&pThis->pPageHint, pPage);
346	break;
347	}
348	}
349	if (iObj >= 0)
350	break;
351	Assert(cLoops != 2);
352	Assert(cLoops < 10);
353	}
354	}
355	Assert(iObj >= 0);
356	Assert((uint32_t)iObj < pThis->cMax);
357
358	/*
359	* Find a free object in the allocation bitmap. Use the new cFree count
360	* as a hint.
361	*/
362	if (ASMAtomicBitTestAndSet(pPage->pbmAlloc, iObj))
363	{
364	for (unsigned cLoops2 = 0;; cLoops2++)
365	{
366	iObj = ASMBitFirstClear(pPage->pbmAlloc, pThis->cBits);
367	if (iObj < 0)
368	ASMMemoryFence();
369	else if (!ASMAtomicBitTestAndSet(pPage->pbmAlloc, iObj))
370	break;
371	Assert(cLoops2 != 2);
372	Assert(cLoops2 != 10);
373	}
374	Assert(iObj >= 0);
375	}
376	void pvObj = &pPage->pbObjects[iObj pThis->cbObject];
377
378	/*
379	* Call the constructor?
380	*/
381	if ( pThis->pfnCtor
382	&& !ASMAtomicBitTestAndSet(pPage->pbmCtor, iObj))
383	{
384	int rc = pThis->pfnCtor(hMemCache, pvObj, pThis->pvUser);
385	if (RT_FAILURE(rc))
386	{
387	ASMAtomicBitClear(pPage->pbmCtor, iObj);
388	RTMemCacheFree(pThis, pvObj);
389	return rc;
390	}
391	}
392
393	return VINF_SUCCESS;
394	}
395
396
397	RTDECL(void *) RTMemCacheAlloc(RTMEMCACHE hMemCache)
398	{
399	void *pvObj;
400	int rc = RTMemCacheAllocEx(hMemCache, &pvObj);
401	if (RT_SUCCESS(rc))
402	return pvObj;
403	return NULL;
404	}
405
406
407	RTDECL(void) RTMemCacheFree(RTMEMCACHE hMemCache, void *pvObj)
408	{
409	if (!pvObj)
410	return;
411
412	RTMEMCACHEINT *pThis = hMemCache;
413	AssertPtrReturnVoid(pThis);
414	AssertReturnVoid(pThis->u32Magic == RTMEMCACHE_MAGIC);
415
416	AssertPtr(pvObj);
417	Assert(RT_ALIGN_P(pvObj, pThis->cbAlignment) == pvObj);
418
419	/* Note: Do NOT attempt to poison the object if we have a constructor
420	or/and destructor! */
421
422	/*
423	* Find the cache page. The page structure is at the start of the page.
424	*/
425	PRTMEMCACHEPAGE pPage = (PRTMEMCACHEPAGE)(((uintptr_t)pvObj) & ~(uintptr_t)PAGE_SIZE);
426	AssertReturnVoid(pPage->pCache == pThis);
427	AssertReturnVoid(ASMAtomicUoReadS32(&pPage->cFree) < (int32_t)pThis->cPerPage);
428
429	/*
430	* Clear the bitmap bit and update the two object counter. Order matters!
431	*/
432	uintptr_t iObj = (uintptr_t)pvObj - (uintptr_t)pPage->pbObjects;
433	AssertReturnVoid(iObj < pThis->cPerPage);
434	AssertReturnVoid(ASMAtomicBitTestAndClear(pPage->pbmAlloc, iObj));
435
436	ASMAtomicIncS32(&pPage->cFree);
437	ASMAtomicIncS32(&pThis->cFree);
438	}
439

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source: vbox/trunk/src/VBox/Runtime/common/alloc/memcache.cpp@ 26417

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