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Fixed two buffer manager performance problems (Markos, Vinayak, thanks for pointing these out!):

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- No longer hold global mutex during page writeback
 
 - Don't reserve 90% of the buffer pool for the free list.  Now the freelist reserves 1% of the buffer pool + 6 pages, and expands if it runs out of space.
This commit is contained in:
Sears Russell 2008-10-01 20:43:58 +00:00
parent cf8eb2ca15
commit 220c33cc31
1 changed files with 54 additions and 27 deletions
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81
src/stasis/bufferManager/bufferHash.c
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@ -196,36 +196,63 @@ static Page * bhLoadPageImpl_helper(int xid, const int pageid, int uninitialized
// Is the page in cache?
Page * ret = LH_ENTRY(find)(cachedPages, &pageid,sizeof(int));
// Is the page already being read from disk? (If ret == 0, then no...)
while(ret) {
checkPageState(ret);
if(*pagePendingPtr(ret)) {
pthread_cond_wait(&readComplete, &mut);
if(ret->id != pageid) {
ret = LH_ENTRY(find)(cachedPages, &pageid, sizeof(int));
}
} else {
#ifdef LATCH_SANITY_CHECKING
int locked = tryreadlock(ret->loadlatch,0);
assert(locked);
#endif
if(! *pagePinCountPtr(ret) ) {
// Then ret is in lru (otherwise it would be pending, or not cached); remove it.
lru->remove(lru, ret);
}
(*pagePinCountPtr(ret))++;
do {
// Is the page already in memory or being read from disk?
// (If ret == 0, then no...)
while(ret) {
checkPageState(ret);
pthread_mutex_unlock(&mut);
assert(ret->id == pageid);
return ret;
if(*pagePendingPtr(ret)) {
pthread_cond_wait(&readComplete, &mut);
if(ret->id != pageid) {
ret = LH_ENTRY(find)(cachedPages, &pageid, sizeof(int));
}
} else {
#ifdef LATCH_SANITY_CHECKING
int locked = tryreadlock(ret->loadlatch,0);
assert(locked);
#endif
if(! *pagePinCountPtr(ret) ) {
// Then ret is in lru (otherwise it would be pending, or not cached); remove it.
lru->remove(lru, ret);
}
(*pagePinCountPtr(ret))++;
checkPageState(ret);
pthread_mutex_unlock(&mut);
assert(ret->id == pageid);
return ret;
}
}
}
// The page is not in cache, and is not (no longer is) pending.
assert(!ret);
// The page is not in cache, and is not (no longer is) pending.
assert(!ret);
// Remove a page from the freelist.
ret = getFreePage();
// Remove a page from the freelist. This may cause writeback, and release our latch.
Page * ret2 = getFreePage();
// Did some other thread put the page in cache for us?
ret = LH_ENTRY(find)(cachedPages, &pageid,sizeof(int));
if(!ret) {
// No, so we're ready to add it.
ret = ret2;
// Esacpe from this loop.
break;
} else {
// Put the page back on the free list
// It's possible that we wrote this page back even though the
// freeList didn't have any free space; extend free list if necessary.
if(freeListLength == freeCount) {
freeList = realloc(freeList, freeListLength+1);
freeListLength++;
}
freeList[freeCount] = ret2;
freeCount++;
}
// try again.
} while(1);
// Add a pending entry to cachedPages to block like-minded threads and writeback
(*pagePendingPtr(ret)) = (void*)1;
@ -371,7 +398,7 @@ void bhBufInit() {
cachedPages = LH_ENTRY(create)(MAX_BUFFER_SIZE);
freeListLength = 9 * MAX_BUFFER_SIZE / 10;
freeListLength = 6 + MAX_BUFFER_SIZE / 100;
freeLowWater = freeListLength - 5;
freeCount = 0;
pageCount = 0;