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Cancel prewarm is LFC limit is reached

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This commit is contained in:
Konstantin Knizhnik
2025-04-14 21:25:54 +03:00
parent c3466e204f
commit c293b96e0a
1 changed files with 15 additions and 12 deletions
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27
pgxn/neon/file_cache.c
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@@ -196,6 +196,8 @@ static int lfc_blocks_per_chunk = MAX_BLOCKS_PER_CHUNK;
static char *lfc_path;
static uint64 lfc_generation;
static FileCacheControl *lfc_ctl;
static bool lfc_do_prewarm;
static bool lfc_prewarm_canceled;
static shmem_startup_hook_type prev_shmem_startup_hook;
#if PG_VERSION_NUM>=150000
static shmem_request_hook_type prev_shmem_request_hook;
@@ -681,7 +683,6 @@ lfc_prewarm(FileCacheState* fcs, uint32 worker_id, uint32 n_workers)
size_t max_prefetch_pages;
size_t prewarm_batch = Min(lfc_prewarm_batch, readahead_buffer_size);
bool save_lfc_store_prefetch_result;
size_t vacant_blocks;
PrewarmWorkerState* ws;
uint8* bitmap;
BufferTag tag;
@@ -734,11 +735,6 @@ lfc_prewarm(FileCacheState* fcs, uint32 worker_id, uint32 n_workers)
LWLockRelease(lfc_lock);
return;
}
vacant_blocks = (size_t)(lfc_ctl->limit - lfc_ctl->size) << lfc_chunk_size_log;
if (n_entries > (vacant_blocks >> fcs_chunk_size_log))
{
n_entries = vacant_blocks >> fcs_chunk_size_log;
}
max_prefetch_pages = n_entries << fcs_chunk_size_log;
if (ws->total_chunks != ws->curr_chunk)
@@ -758,12 +754,15 @@ lfc_prewarm(FileCacheState* fcs, uint32 worker_id, uint32 n_workers)
save_lfc_store_prefetch_result = lfc_store_prefetch_result;
lfc_store_prefetch_result = true;
lfc_do_prewarm = true; /* Flag for lfc_prefetch preventing replacement of existed entries if LFC ache is full */
lfc_prewarm_canceled = false; /* Flag set if prewarm is canceled because LFC limit is reached */
elog(LOG, "LFC: start loading %ld chunks", (long)n_entries);
PG_TRY();
{
while (true)
{
if (snd_idx < max_prefetch_pages)
if (snd_idx < max_prefetch_pages && !lfc_prewarm_canceled)
{
if ((snd_idx >> fcs_chunk_size_log) % n_workers != worker_id)
{
@@ -789,9 +788,9 @@ lfc_prewarm(FileCacheState* fcs, uint32 worker_id, uint32 n_workers)
snd_idx += 1;
}
}
if (n_sent >= n_received + prewarm_batch || snd_idx == max_prefetch_pages)
if (n_sent >= n_received + prewarm_batch || snd_idx == max_prefetch_pages || lfc_prewarm_canceled)
{
if (n_received == n_sent && snd_idx == max_prefetch_pages)
if (n_received == n_sent && (snd_idx == max_prefetch_pages || lfc_prewarm_canceled))
{
break;
}
@@ -831,6 +830,7 @@ lfc_prewarm(FileCacheState* fcs, uint32 worker_id, uint32 n_workers)
{
lfc_store_prefetch_result = save_lfc_store_prefetch_result;
ws->curr_chunk = n_entries;
lfc_do_prewarm = false;
}
PG_END_TRY();
}
@@ -1274,8 +1274,11 @@ lfc_init_new_entry(FileCacheEntry* entry, uint32 hash)
* If we can't (e.g. because all other slots are being accessed)
* then we will remove this entry from the hash and continue
* on to the next chunk, as we may not exceed the limit.
*
* While prewarming LFC we do not want to replcate existed entries,
* so we just stop prewarm is LFC cache is full.
*/
else if (!dlist_is_empty(&lfc_ctl->lru))
else if (!dlist_is_empty(&lfc_ctl->lru) && !lfc_do_prewarm)
{
/* Cache overflow: evict least recently used chunk */
FileCacheEntry *victim = dlist_container(FileCacheEntry, list_node,
@@ -1299,7 +1302,7 @@ lfc_init_new_entry(FileCacheEntry* entry, uint32 hash)
/* Can't add this chunk - we don't have the space for it */
hash_search_with_hash_value(lfc_hash, &entry->key, hash,
HASH_REMOVE, NULL);
lfc_prewarm_canceled = true; /* cancel prewarm if LFC limit is reached */
return false;
}
@@ -1373,7 +1376,7 @@ lfc_prefetch(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
LWLockRelease(lfc_lock);
return false;
}
lwlsn = neon_get_lwlsn(rinfo, forknum, blkno);
if (lwlsn > lsn)