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Eliminate stale reads from LFC in case of prewarm conflict

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This commit is contained in:
Konstantin Knizhnik
2024-12-14 21:58:26 +02:00
parent 07027bde7d
commit 1d77fb0dea
1 changed files with 18 additions and 11 deletions
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29
pgxn/neon/file_cache.c
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@@ -1162,6 +1162,14 @@ lfc_writev(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
CriticalAssert(BufTagGetRelNumber(&tag) != InvalidRelFileNumber);
LWLockAcquire(lfc_lock, LW_EXCLUSIVE);
if (!LFC_ENABLED())
{
LWLockRelease(lfc_lock);
return;
}
/*
* For every chunk that has blocks we're interested in, we
* 1. get the chunk header
@@ -1188,14 +1196,6 @@ lfc_writev(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
tag.blockNum = blkno & ~(BLOCKS_PER_CHUNK - 1);
hash = get_hash_value(lfc_hash, &tag);
LWLockAcquire(lfc_lock, LW_EXCLUSIVE);
if (!LFC_ENABLED())
{
LWLockRelease(lfc_lock);
return;
}
entry = hash_search_with_hash_value(lfc_hash, &tag, hash, HASH_ENTER, &found);
if (found)
@@ -1208,8 +1208,13 @@ lfc_writev(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
* But clearing `prewarm_requested` flag also will not allow `lfc_prewarm` to fix it result.
*/
entry->prewarm_requested = false;
LWLockRelease(lfc_lock);
return;
/* cleanup all affected pages of the chunk: we do not know which one of them is conflicting with prewarm */
for (int i = 0; i < blocks_in_chunk; i++)
{
lfc_ctl->used_pages -= ((entry->bitmap[(chunk_offs + i) >> 5] >> ((chunk_offs + i) & 31)) & 1);
entry->bitmap[(chunk_offs + i) >> 5] &= ~(1 << ((chunk_offs + i) & 31));
}
goto next_chunk;
}
/*
* Unlink entry from LRU list to pin it for the duration of IO
@@ -1290,6 +1295,7 @@ lfc_writev(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
if (rc != BLCKSZ * blocks_in_chunk)
{
lfc_disable("write");
return;
}
else
{
@@ -1319,12 +1325,13 @@ lfc_writev(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
}
}
LWLockRelease(lfc_lock);
}
next_chunk:
blkno += blocks_in_chunk;
buf_offset += blocks_in_chunk;
nblocks -= blocks_in_chunk;
}
LWLockRelease(lfc_lock);
}
typedef struct