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bufmgr: Add Pin/UnpinLocalBuffer()

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So far these were open-coded in quite a few places, without a good reason.

Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/20221029025420.eplyow6k7tgu6he3@awork3.anarazel.de
This commit is contained in:
Andres Freund
2023-04-05 10:42:17 -07:00
parent 819b69a81d
commit 794f259447
3 changed files with 51 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
src/backend/storage/buffer/bufmgr.c
View File

@ -636,20 +636,7 @@ ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockN
/* Is it still valid and holding the right tag? */
if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
{
/*
* Bump buffer's ref and usage counts. This is equivalent of
* PinBuffer for a shared buffer.
*/
if (LocalRefCount[b] == 0)
{
if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
{
buf_state += BUF_USAGECOUNT_ONE;
pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
}
}
LocalRefCount[b]++;
ResourceOwnerRememberBuffer(CurrentResourceOwner, recent_buffer);
PinLocalBuffer(bufHdr, true);
pgBufferUsage.local_blks_hit++;
@ -1688,8 +1675,7 @@ ReleaseAndReadBuffer(Buffer buffer,
BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
BufTagGetForkNum(&bufHdr->tag) == forkNum)
return buffer;
ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
LocalRefCount[-buffer - 1]--;
UnpinLocalBuffer(buffer);
}
else
{
@ -3982,15 +3968,9 @@ ReleaseBuffer(Buffer buffer)
elog(ERROR, "bad buffer ID: %d", buffer);
if (BufferIsLocal(buffer))
{
ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
Assert(LocalRefCount[-buffer - 1] > 0);
LocalRefCount[-buffer - 1]--;
return;
}
UnpinBuffer(GetBufferDescriptor(buffer - 1));
UnpinLocalBuffer(buffer);
else
UnpinBuffer(GetBufferDescriptor(buffer - 1));
}
/*

67
src/backend/storage/buffer/localbuf.c
View File

@ -137,27 +137,8 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum,
fprintf(stderr, "LB ALLOC (%u,%d,%d) %d\n",
smgr->smgr_rlocator.locator.relNumber, forkNum, blockNum, -b - 1);
#endif
buf_state = pg_atomic_read_u32(&bufHdr->state);
/* this part is equivalent to PinBuffer for a shared buffer */
if (LocalRefCount[b] == 0)
{
if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
{
buf_state += BUF_USAGECOUNT_ONE;
pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
}
}
LocalRefCount[b]++;
ResourceOwnerRememberBuffer(CurrentResourceOwner,
BufferDescriptorGetBuffer(bufHdr));
if (buf_state & BM_VALID)
*foundPtr = true;
else
{
/* Previous read attempt must have failed; try again */
*foundPtr = false;
}
*foundPtr = PinLocalBuffer(bufHdr, true);
return bufHdr;
}
@ -194,9 +175,7 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum,
else
{
/* Found a usable buffer */
LocalRefCount[b]++;
ResourceOwnerRememberBuffer(CurrentResourceOwner,
BufferDescriptorGetBuffer(bufHdr));
PinLocalBuffer(bufHdr, false);
break;
}
}
@ -484,6 +463,48 @@ InitLocalBuffers(void)
NLocBuffer = nbufs;
}
/*
* XXX: We could have a slightly more efficient version of PinLocalBuffer()
* that does not support adjusting the usagecount - but so far it does not
* seem worth the trouble.
*/
bool
PinLocalBuffer(BufferDesc *buf_hdr, bool adjust_usagecount)
{
uint32 buf_state;
Buffer buffer = BufferDescriptorGetBuffer(buf_hdr);
int bufid = -buffer - 1;
buf_state = pg_atomic_read_u32(&buf_hdr->state);
if (LocalRefCount[bufid] == 0)
{
if (adjust_usagecount &&
BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
{
buf_state += BUF_USAGECOUNT_ONE;
pg_atomic_unlocked_write_u32(&buf_hdr->state, buf_state);
}
}
LocalRefCount[bufid]++;
ResourceOwnerRememberBuffer(CurrentResourceOwner,
BufferDescriptorGetBuffer(buf_hdr));
return buf_state & BM_VALID;
}
void
UnpinLocalBuffer(Buffer buffer)
{
int buffid = -buffer - 1;
Assert(BufferIsLocal(buffer));
Assert(LocalRefCount[buffid] > 0);
ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
LocalRefCount[buffid]--;
}
/*
* GUC check_hook for temp_buffers
*/

2
src/include/storage/buf_internals.h
View File

@ -415,6 +415,8 @@ extern int BufTableInsert(BufferTag *tagPtr, uint32 hashcode, int buf_id);
extern void BufTableDelete(BufferTag *tagPtr, uint32 hashcode);
/* localbuf.c */
extern bool PinLocalBuffer(BufferDesc *buf_hdr, bool adjust_usagecount);
extern void UnpinLocalBuffer(Buffer buffer);
extern PrefetchBufferResult PrefetchLocalBuffer(SMgrRelation smgr,
ForkNumber forkNum,
BlockNumber blockNum);