Changeset 24517 in vbox

Timestamp:

Nov 9, 2009 4:03:09 PM (15 years ago)

Author:

vboxsync

Message:

AsyncCompletion: Reuse evicted buffers if possible to avoid too much free/allocation calls

Location:

trunk/src/VBox/VMM

Files:

• PDMAsyncCompletionFileCache.cpp (modified) (22 diffs)
• PDMAsyncCompletionFileInternal.h (modified) (2 diffs)

trunk/src/VBox/VMM/PDMAsyncCompletionFileCache.cpp

@@ -232 +232 @@
  * @param    pGhostListSrc    The ghost list removed entries should be moved to
  *                            NULL if the entry should be freed.
+ * @param    fReuseBuffer     Flag whether a buffer should be reused if it has the same size
+ * @param    ppbBuf           Where to store the address of the buffer if an entry with the
+ *                            same size was found and fReuseBuffer is true.
  *
  * @notes This function may return fewer bytes than requested because entries
@@ -237 +240 @@
  */
 static size_t pdmacFileCacheEvictPagesFrom(PPDMACFILECACHEGLOBAL pCache, size_t cbData,
-                                           PPDMACFILELRULIST pListSrc, PPDMACFILELRULIST pGhostListDst)
+                                           PPDMACFILELRULIST pListSrc, PPDMACFILELRULIST pGhostListDst,
+                                           bool fReuseBuffer, uint8_t **ppbBuffer)
 {
     size_t cbEvicted = 0;
@@ -248 +252 @@
               || (pGhostListDst == &pCache->LruFrequentlyGhost),
               ("Destination list must be NULL or one of the ghost lists\n"));
+
+    if (fReuseBuffer)
+    {
+        AssertPtr(ppbBuffer);
+        *ppbBuffer = NULL;
+    }
 
     /* Start deleting from the tail. */
@@ -276 +286 @@
                 LogFlow(("Evicting entry %#p (%u bytes)\n", pCurr, pCurr->cbData));
 
-                if (pCurr->pbData)
+                if (fReuseBuffer && (pCurr->cbData == cbData))
                 {
+                    STAM_COUNTER_INC(&pCache->StatBuffersReused);
+                    *ppbBuffer = pCurr->pbData;
+                }
+                else if (pCurr->pbData)
                     RTMemPageFree(pCurr->pbData);
-                    pCurr->pbData = NULL;
-                }
-
+
+                pCurr->pbData = NULL;
                 cbEvicted += pCurr->cbData;
 
@@ -310 +323 @@
 }
 
-static size_t pdmacFileCacheReplace(PPDMACFILECACHEGLOBAL pCache, size_t cbData, PPDMACFILELRULIST pEntryList)
+static size_t pdmacFileCacheReplace(PPDMACFILECACHEGLOBAL pCache, size_t cbData, PPDMACFILELRULIST pEntryList,
+                                    bool fReuseBuffer, uint8_t **ppbBuffer)
 {
     PDMACFILECACHE_IS_CRITSECT_OWNER(pCache);
@@ -322 +336 @@
         return pdmacFileCacheEvictPagesFrom(pCache, cbData,
                                             &pCache->LruRecentlyUsed,
-                                            &pCache->LruRecentlyGhost);
+                                            &pCache->LruRecentlyGhost,
+                                            fReuseBuffer, ppbBuffer);
     }
     else
@@ -329 +344 @@
         return pdmacFileCacheEvictPagesFrom(pCache, cbData,
                                             &pCache->LruFrequentlyUsed,
-                                            &pCache->LruFrequentlyGhost);
+                                            &pCache->LruFrequentlyGhost,
+                                            fReuseBuffer, ppbBuffer);
     }
 }
@@ -340 +356 @@
  * @param    cbData    Number of bytes to evict.
  */
-static size_t pdmacFileCacheEvict(PPDMACFILECACHEGLOBAL pCache, size_t cbData)
+static size_t pdmacFileCacheEvict(PPDMACFILECACHEGLOBAL pCache, size_t cbData, bool fReuseBuffer, uint8_t **ppbBuffer)
 {
     size_t cbRemoved = ~0;
@@ -353 +369 @@
             cbRemoved = pdmacFileCacheEvictPagesFrom(pCache, cbData,
                                                      &pCache->LruRecentlyGhost,
-                                                     NULL);
+                                                     NULL,
+                                                     fReuseBuffer, ppbBuffer);
         }
         else
@@ -359 +376 @@
             cbRemoved = pdmacFileCacheEvictPagesFrom(pCache, cbData,
                                                      &pCache->LruRecentlyUsed,
-                                                     NULL);
+                                                     NULL,
+                                                     fReuseBuffer, ppbBuffer);
         }
     }
@@ -372 +390 @@
                 cbRemoved = pdmacFileCacheEvictPagesFrom(pCache, cbData,
                                                          &pCache->LruFrequentlyGhost,
-                                                         NULL);
+                                                         NULL,
+                                                         fReuseBuffer, ppbBuffer);
 
             if (cbRemoved >= cbData)
-                cbRemoved = pdmacFileCacheReplace(pCache, cbData, NULL);
+                cbRemoved = pdmacFileCacheReplace(pCache, cbData, NULL, fReuseBuffer, ppbBuffer);
         }
     }
@@ -677 +696 @@
                    "/PDM/AsyncCompletion/File/CacheTreeRemove",
                    STAMUNIT_TICKS_PER_CALL, "Time taken to remove an entry an the tree");
+    STAMR3Register(pClassFile->Core.pVM, &pCache->StatBuffersReused,
+                   STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS,
+                   "/PDM/AsyncCompletion/File/CacheBuffersReused",
+                   STAMUNIT_COUNT, "Number of times a buffer could be reused");
 #endif
 
@@ -866 +889 @@
  * @param   off       Start offset.
  * @param   cbData    Size of the cache entry.
+ * @param   pbBuffer  Pointer to the buffer to use.
+ *                    NULL if a new buffer should be allocated.
+ *                    The buffer needs to have the same size of the entry. 
  */
 static PPDMACFILECACHEENTRY pdmacFileCacheEntryAlloc(PPDMACFILECACHEGLOBAL pCache,
                                                      PPDMASYNCCOMPLETIONENDPOINTFILE pEndpoint,
-                                                     RTFOFF off, size_t cbData)
+                                                     RTFOFF off, size_t cbData, uint8_t *pbBuffer)
 {
     PPDMACFILECACHEENTRY pEntryNew = (PPDMACFILECACHEENTRY)RTMemAllocZ(sizeof(PDMACFILECACHEENTRY));
@@ -887 +913 @@
     pEntryNew->pWaitingTail  = NULL;
     pEntryNew->pbDataReplace = NULL;
-    pEntryNew->pbData        = (uint8_t *)RTMemPageAlloc(cbData);
+    if (pbBuffer)
+        pEntryNew->pbData    = pbBuffer;
+    else
+        pEntryNew->pbData    = (uint8_t *)RTMemPageAlloc(cbData);
 
     if (RT_UNLIKELY(!pEntryNew->pbData))
@@ -1124 +1153 @@
             else
             {
+                uint8_t *pbBuffer = NULL;
+
                 LogFlow(("Fetching data for ghost entry %#p from file\n", pEntry));
 
                 RTCritSectEnter(&pCache->CritSect);
                 pdmacFileCacheUpdate(pCache, pEntry);
-                pdmacFileCacheReplace(pCache, pEntry->cbData, pEntry->pList);
+                pdmacFileCacheReplace(pCache, pEntry->cbData, pEntry->pList, true, &pbBuffer);
 
                 /* Move the entry to T2 and fetch it to the cache. */
@@ -1134 +1165 @@
                 RTCritSectLeave(&pCache->CritSect);
 
-                pEntry->pbData  = (uint8_t *)RTMemPageAlloc(pEntry->cbData);
+                if (pbBuffer)
+                    pEntry->pbData = pbBuffer;
+                else
+                    pEntry->pbData = (uint8_t *)RTMemPageAlloc(pEntry->cbData);
                 AssertPtr(pEntry->pbData);
 
@@ -1206 +1240 @@
                 STAM_COUNTER_INC(&pCache->cPartialHits);
 
+            uint8_t *pbBuffer = NULL;
+
             RTCritSectEnter(&pCache->CritSect);
-            size_t cbRemoved = pdmacFileCacheEvict(pCache, cbToReadAligned);
+            size_t cbRemoved = pdmacFileCacheEvict(pCache, cbToReadAligned, true, &pbBuffer);
             RTCritSectLeave(&pCache->CritSect);
 
@@ -1213 +1249 @@
             {
                 LogFlow(("Evicted %u bytes (%u requested). Creating new cache entry\n", cbRemoved, cbToReadAligned));
-                PPDMACFILECACHEENTRY pEntryNew = pdmacFileCacheEntryAlloc(pCache, pEndpoint, off, cbToReadAligned);
+                PPDMACFILECACHEENTRY pEntryNew = pdmacFileCacheEntryAlloc(pCache, pEndpoint, off, cbToReadAligned, pbBuffer);
                 AssertPtr(pEntryNew);
 
@@ -1517 +1553 @@
             else
             {
+                uint8_t *pbBuffer = NULL;
+
                 RTCritSectEnter(&pCache->CritSect);
                 pdmacFileCacheUpdate(pCache, pEntry);
-                pdmacFileCacheReplace(pCache, pEntry->cbData, pEntry->pList);
+                pdmacFileCacheReplace(pCache, pEntry->cbData, pEntry->pList, true, &pbBuffer);
 
                 /* Move the entry to T2 and fetch it to the cache. */
@@ -1525 +1563 @@
                 RTCritSectLeave(&pCache->CritSect);
 
-                pEntry->pbData  = (uint8_t *)RTMemPageAlloc(pEntry->cbData);
+                if (pbBuffer)
+                    pEntry->pbData = pbBuffer;
+                else
+                    pEntry->pbData = (uint8_t *)RTMemPageAlloc(pEntry->cbData);
                 AssertPtr(pEntry->pbData);
 
@@ -1586 +1627 @@
             STAM_COUNTER_ADD(&pCache->StatWritten, cbToWrite);
 
+            uint8_t *pbBuffer = NULL;
+
             RTCritSectEnter(&pCache->CritSect);
-            size_t cbRemoved = pdmacFileCacheEvict(pCache, cbToWrite);
+            size_t cbRemoved = pdmacFileCacheEvict(pCache, cbToWrite, true, &pbBuffer);
             RTCritSectLeave(&pCache->CritSect);
 
@@ -1597 +1640 @@
                 LogFlow(("Evicted %u bytes (%u requested). Creating new cache entry\n", cbRemoved, cbToWrite));
 
-                pEntryNew = pdmacFileCacheEntryAlloc(pCache, pEndpoint, off, cbToWrite);
+                pEntryNew = pdmacFileCacheEntryAlloc(pCache, pEndpoint, off, cbToWrite, pbBuffer);
                 AssertPtr(pEntryNew);
 

trunk/src/VBox/VMM/PDMAsyncCompletionFileInternal.h

@@ -249 +249 @@
 #define PDMACFILECACHE_ENTRY_IS_DEPRECATED  RT_BIT(3)
 /** Entry is not evictable. */
-#define PDMACFILECACHE_NOT_EVICTABLE  (PDMACFILECACHE_ENTRY_LOCKED | PDMACFILECACHE_IO_IN_PROGRESS)
+#define PDMACFILECACHE_NOT_EVICTABLE  (PDMACFILECACHE_ENTRY_LOCKED | PDMACFILECACHE_IO_IN_PROGRESS | PDMACFILECACHE_ENTRY_IS_DEPRECATED)
 
 /**
@@ -302 +302 @@
     /** Time spend to remove an entry in the AVL tree. */
     STAMPROFILEADV   StatTreeRemove;
+    /** Number of times a buffer could be reused. */
+    STAMCOUNTER      StatBuffersReused;
 #endif
 } PDMACFILECACHEGLOBAL;