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Commit719c84c

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Extend relations multiple blocks at a time to improve scalability.
Contention on the relation extension lock can become quite fierce whenmultiple processes are inserting data into the same relation at the sametime at a high rate. Experimentation shows the extending the relationmultiple blocks at a time improves scalability.Dilip Kumar, reviewed by Petr Jelinek, Amit Kapila, and me.
1 parent8643b91 commit719c84c

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7 files changed

+271
-3
lines changed

7 files changed

+271
-3
lines changed

‎src/backend/access/heap/hio.c

Lines changed: 109 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -168,6 +168,75 @@ GetVisibilityMapPins(Relation relation, Buffer buffer1, Buffer buffer2,
168168
}
169169
}
170170

171+
/*
172+
* Extend a relation by multiple blocks to avoid future contention on the
173+
* relation extension lock. Our goal is to pre-extend the relation by an
174+
* amount which ramps up as the degree of contention ramps up, but limiting
175+
* the result to some sane overall value.
176+
*/
177+
staticvoid
178+
RelationAddExtraBlocks(Relationrelation,BulkInsertStatebistate)
179+
{
180+
Pagepage;
181+
BlockNumberblockNum=InvalidBlockNumber,
182+
firstBlock=InvalidBlockNumber;
183+
intextraBlocks=0;
184+
intlockWaiters=0;
185+
Sizefreespace=0;
186+
Bufferbuffer;
187+
188+
/* Use the length of the lock wait queue to judge how much to extend. */
189+
lockWaiters=RelationExtensionLockWaiterCount(relation);
190+
if (lockWaiters <=0)
191+
return;
192+
193+
/*
194+
* It might seem like multiplying the number of lock waiters by as much
195+
* as 20 is too aggressive, but benchmarking revealed that smaller numbers
196+
* were insufficient. 512 is just an arbitrary cap to prevent pathological
197+
* results.
198+
*/
199+
extraBlocks=Min(512,lockWaiters*20);
200+
201+
while (extraBlocks-- >=0)
202+
{
203+
/* Ouch - an unnecessary lseek() each time through the loop! */
204+
buffer=ReadBufferBI(relation,P_NEW,bistate);
205+
206+
/* Extend by one page. */
207+
LockBuffer(buffer,BUFFER_LOCK_EXCLUSIVE);
208+
page=BufferGetPage(buffer);
209+
PageInit(page,BufferGetPageSize(buffer),0);
210+
MarkBufferDirty(buffer);
211+
blockNum=BufferGetBlockNumber(buffer);
212+
freespace=PageGetHeapFreeSpace(page);
213+
UnlockReleaseBuffer(buffer);
214+
215+
/* Remember first block number thus added. */
216+
if (firstBlock==InvalidBlockNumber)
217+
firstBlock=blockNum;
218+
219+
/*
220+
* Immediately update the bottom level of the FSM. This has a good
221+
* chance of making this page visible to other concurrently inserting
222+
* backends, and we want that to happen without delay.
223+
*/
224+
RecordPageWithFreeSpace(relation,blockNum,freespace);
225+
}
226+
227+
/*
228+
* Updating the upper levels of the free space map is too expensive
229+
* to do for every block, but it's worth doing once at the end to make
230+
* sure that subsequent insertion activity sees all of those nifty free
231+
* pages we just inserted.
232+
*
233+
* Note that we're using the freespace value that was reported for the
234+
* last block we added as if it were the freespace value for every block
235+
* we added. That's actually true, because they're all equally empty.
236+
*/
237+
UpdateFreeSpaceMap(relation,firstBlock,blockNum,freespace);
238+
}
239+
171240
/*
172241
* RelationGetBufferForTuple
173242
*
@@ -233,8 +302,8 @@ RelationGetBufferForTuple(Relation relation, Size len,
233302
booluse_fsm= !(options&HEAP_INSERT_SKIP_FSM);
234303
Bufferbuffer=InvalidBuffer;
235304
Pagepage;
236-
SizepageFreeSpace,
237-
saveFreeSpace;
305+
SizepageFreeSpace=0,
306+
saveFreeSpace=0;
238307
BlockNumbertargetBlock,
239308
otherBlock;
240309
boolneedLock;
@@ -308,6 +377,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
308377
}
309378
}
310379

380+
loop:
311381
while (targetBlock!=InvalidBlockNumber)
312382
{
313383
/*
@@ -440,10 +510,46 @@ RelationGetBufferForTuple(Relation relation, Size len,
440510
*/
441511
needLock= !RELATION_IS_LOCAL(relation);
442512

513+
/*
514+
* If we need the lock but are not able to acquire it immediately, we'll
515+
* consider extending the relation by multiple blocks at a time to manage
516+
* contention on the relation extension lock. However, this only makes
517+
* sense if we're using the FSM; otherwise, there's no point.
518+
*/
443519
if (needLock)
444-
LockRelationForExtension(relation,ExclusiveLock);
520+
{
521+
if (!use_fsm)
522+
LockRelationForExtension(relation,ExclusiveLock);
523+
elseif (!ConditionalLockRelationForExtension(relation,ExclusiveLock))
524+
{
525+
/* Couldn't get the lock immediately; wait for it. */
526+
LockRelationForExtension(relation,ExclusiveLock);
527+
528+
/*
529+
* Check if some other backend has extended a block for us while
530+
* we were waiting on the lock.
531+
*/
532+
targetBlock=GetPageWithFreeSpace(relation,len+saveFreeSpace);
533+
534+
/*
535+
* If some other waiter has already extended the relation, we
536+
* don't need to do so; just use the existing freespace.
537+
*/
538+
if (targetBlock!=InvalidBlockNumber)
539+
{
540+
UnlockRelationForExtension(relation,ExclusiveLock);
541+
gotoloop;
542+
}
543+
544+
/* Time to bulk-extend. */
545+
RelationAddExtraBlocks(relation,bistate);
546+
}
547+
}
445548

446549
/*
550+
* In addition to whatever extension we performed above, we always add
551+
* at least one block to satisfy our own request.
552+
*
447553
* XXX This does an lseek - rather expensive - but at the moment it is the
448554
* only way to accurately determine how many blocks are in a relation. Is
449555
* it worth keeping an accurate file length in shared memory someplace,

‎src/backend/storage/freespace/freespace.c

Lines changed: 81 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -109,6 +109,8 @@ static int fsm_set_and_search(Relation rel, FSMAddress addr, uint16 slot,
109109
uint8newValue,uint8minValue);
110110
staticBlockNumberfsm_search(Relationrel,uint8min_cat);
111111
staticuint8fsm_vacuum_page(Relationrel,FSMAddressaddr,bool*eof);
112+
staticBlockNumberfsm_get_lastblckno(Relationrel,FSMAddressaddr);
113+
staticvoidfsm_update_recursive(Relationrel,FSMAddressaddr,uint8new_cat);
112114

113115

114116
/******** Public API ********/
@@ -188,6 +190,46 @@ RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk, Size spaceAvail)
188190
fsm_set_and_search(rel,addr,slot,new_cat,0);
189191
}
190192

193+
/*
194+
* Update the upper levels of the free space map all the way up to the root
195+
* to make sure we don't lose track of new blocks we just inserted. This is
196+
* intended to be used after adding many new blocks to the relation; we judge
197+
* it not worth updating the upper levels of the tree every time data for
198+
* a single page changes, but for a bulk-extend it's worth it.
199+
*/
200+
void
201+
UpdateFreeSpaceMap(Relationrel,BlockNumberstartBlkNum,
202+
BlockNumberendBlkNum,Sizefreespace)
203+
{
204+
intnew_cat=fsm_space_avail_to_cat(freespace);
205+
FSMAddressaddr;
206+
uint16slot;
207+
BlockNumberblockNum;
208+
BlockNumberlastBlkOnPage;
209+
210+
blockNum=startBlkNum;
211+
212+
while (blockNum <=endBlkNum)
213+
{
214+
/*
215+
* Find FSM address for this block; update tree all the way to the
216+
* root.
217+
*/
218+
addr=fsm_get_location(blockNum,&slot);
219+
fsm_update_recursive(rel,addr,new_cat);
220+
221+
/*
222+
* Get the last block number on this FSM page. If that's greater
223+
* than or equal to our endBlkNum, we're done. Otherwise, advance
224+
* to the first block on the next page.
225+
*/
226+
lastBlkOnPage=fsm_get_lastblckno(rel,addr);
227+
if (lastBlkOnPage >=endBlkNum)
228+
break;
229+
blockNum=lastBlkOnPage+1;
230+
}
231+
}
232+
191233
/*
192234
* XLogRecordPageWithFreeSpace - like RecordPageWithFreeSpace, for use in
193235
*WAL replay
@@ -788,3 +830,42 @@ fsm_vacuum_page(Relation rel, FSMAddress addr, bool *eof_p)
788830

789831
returnmax_avail;
790832
}
833+
834+
/*
835+
* This function will return the last block number stored on given
836+
* FSM page address.
837+
*/
838+
staticBlockNumber
839+
fsm_get_lastblckno(Relationrel,FSMAddressaddr)
840+
{
841+
intslot;
842+
843+
/*
844+
* Get the last slot number on the given address and convert that to
845+
* block number
846+
*/
847+
slot=SlotsPerFSMPage-1;
848+
returnfsm_get_heap_blk(addr,slot);
849+
}
850+
851+
/*
852+
* Recursively update the FSM tree from given address to
853+
* all the way up to root.
854+
*/
855+
staticvoid
856+
fsm_update_recursive(Relationrel,FSMAddressaddr,uint8new_cat)
857+
{
858+
uint16parentslot;
859+
FSMAddressparent;
860+
861+
if (addr.level==FSM_ROOT_LEVEL)
862+
return;
863+
864+
/*
865+
* Get the parent page and our slot in the parent page, and
866+
* update the information in that.
867+
*/
868+
parent=fsm_get_parent(addr,&parentslot);
869+
fsm_set_and_search(rel,parent,parentslot,new_cat,0);
870+
fsm_update_recursive(rel,parent,new_cat);
871+
}

‎src/backend/storage/lmgr/lmgr.c

Lines changed: 35 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -340,6 +340,41 @@ LockRelationForExtension(Relation relation, LOCKMODE lockmode)
340340
(void)LockAcquire(&tag,lockmode, false, false);
341341
}
342342

343+
/*
344+
*ConditionalLockRelationForExtension
345+
*
346+
* As above, but only lock if we can get the lock without blocking.
347+
* Returns TRUE iff the lock was acquired.
348+
*/
349+
bool
350+
ConditionalLockRelationForExtension(Relationrelation,LOCKMODElockmode)
351+
{
352+
LOCKTAGtag;
353+
354+
SET_LOCKTAG_RELATION_EXTEND(tag,
355+
relation->rd_lockInfo.lockRelId.dbId,
356+
relation->rd_lockInfo.lockRelId.relId);
357+
358+
return (LockAcquire(&tag,lockmode, false, true)!=LOCKACQUIRE_NOT_AVAIL);
359+
}
360+
361+
/*
362+
*RelationExtensionLockWaiterCount
363+
*
364+
* Count the number of processes waiting for the given relation extension lock.
365+
*/
366+
int
367+
RelationExtensionLockWaiterCount(Relationrelation)
368+
{
369+
LOCKTAGtag;
370+
371+
SET_LOCKTAG_RELATION_EXTEND(tag,
372+
relation->rd_lockInfo.lockRelId.dbId,
373+
relation->rd_lockInfo.lockRelId.relId);
374+
375+
returnLockWaiterCount(&tag);
376+
}
377+
343378
/*
344379
*UnlockRelationForExtension
345380
*/

‎src/backend/storage/lmgr/lock.c

Lines changed: 37 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4380,3 +4380,40 @@ VirtualXactLock(VirtualTransactionId vxid, bool wait)
43804380
LockRelease(&tag,ShareLock, false);
43814381
return true;
43824382
}
4383+
4384+
/*
4385+
* LockWaiterCount
4386+
*
4387+
* Find the number of lock requester on this locktag
4388+
*/
4389+
int
4390+
LockWaiterCount(constLOCKTAG*locktag)
4391+
{
4392+
LOCKMETHODIDlockmethodid=locktag->locktag_lockmethodid;
4393+
LOCK*lock;
4394+
boolfound;
4395+
uint32hashcode;
4396+
LWLock*partitionLock;
4397+
intwaiters=0;
4398+
4399+
if (lockmethodid <=0||lockmethodid >=lengthof(LockMethods))
4400+
elog(ERROR,"unrecognized lock method: %d",lockmethodid);
4401+
4402+
hashcode=LockTagHashCode(locktag);
4403+
partitionLock=LockHashPartitionLock(hashcode);
4404+
LWLockAcquire(partitionLock,LW_EXCLUSIVE);
4405+
4406+
lock= (LOCK*)hash_search_with_hash_value(LockMethodLockHash,
4407+
(constvoid*)locktag,
4408+
hashcode,
4409+
HASH_FIND,
4410+
&found);
4411+
if (found)
4412+
{
4413+
Assert(lock!=NULL);
4414+
waiters=lock->nRequested;
4415+
}
4416+
LWLockRelease(partitionLock);
4417+
4418+
returnwaiters;
4419+
}

‎src/include/storage/freespace.h

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -32,5 +32,9 @@ extern void XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
3232

3333
externvoidFreeSpaceMapTruncateRel(Relationrel,BlockNumbernblocks);
3434
externvoidFreeSpaceMapVacuum(Relationrel);
35+
externvoidUpdateFreeSpaceMap(Relationrel,
36+
BlockNumberfirtsBlkNum,
37+
BlockNumberlastBlkNum,
38+
Sizefreespace);
3539

3640
#endif/* FREESPACE_H_ */

‎src/include/storage/lmgr.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,9 @@ extern void UnlockRelationIdForSession(LockRelId *relid, LOCKMODE lockmode);
5353
/* Lock a relation for extension */
5454
externvoidLockRelationForExtension(Relationrelation,LOCKMODElockmode);
5555
externvoidUnlockRelationForExtension(Relationrelation,LOCKMODElockmode);
56+
externboolConditionalLockRelationForExtension(Relationrelation,
57+
LOCKMODElockmode);
58+
externintRelationExtensionLockWaiterCount(Relationrelation);
5659

5760
/* Lock a page (currently only used within indexes) */
5861
externvoidLockPage(Relationrelation,BlockNumberblkno,LOCKMODElockmode);

‎src/include/storage/lock.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -574,6 +574,8 @@ extern void RememberSimpleDeadLock(PGPROC *proc1,
574574
PGPROC*proc2);
575575
externvoidInitDeadLockChecking(void);
576576

577+
externintLockWaiterCount(constLOCKTAG*locktag);
578+
577579
#ifdefLOCK_DEBUG
578580
externvoidDumpLocks(PGPROC*proc);
579581
externvoidDumpAllLocks(void);

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