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Reduce overhead of cache-clobber testing in LookupOpclassInfo().
Commit03ffc4d6d
added logic to bypass all caching behavior in LookupOpclassInfo when CLOBBER_CACHE_ALWAYS is enabled. It doesn't look like I stopped to think much about what that would cost, but recent investigation shows that the cost is enormous: it roughly doubles the time needed for cache-clobber test runs. There does seem to be value in this behavior when trying to test the opclass-cache loading logic itself, but for other purposes the cost is excessive. Hence, let's back off to doing this only when debug_invalidate_system_caches_always is at least 3; or in older branches, when CLOBBER_CACHE_RECURSIVELY is defined. While here, clean up some other minor issues in LookupOpclassInfo. Re-order the code so we aren't left with broken cache entries (leading to later core dumps) in the unlikely case that we suffer OOM while trying to allocate space for a new entry. (That seems to be my oversight in 03ffc4d6d.) Also, in >= v13, stop allocating one array entry too many. That's evidently left over from sloppy reversion in851b14b0c
. Back-patch to all supported branches, mainly to reduce the runtime of cache-clobbering buildfarm animals. Discussion: https://postgr.es/m/1370856.1625428625@sss.pgh.pa.us
This commit is contained in:
parent
73ede4da6b
commit
3edc2dbc00
43
src/backend/utils/cache/relcache.c
vendored
43
src/backend/utils/cache/relcache.c
vendored
@ -1612,15 +1612,15 @@ LookupOpclassInfo(Oid operatorClassOid,
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/* First time through: initialize the opclass cache */
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HASHCTL ctl;
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/* Also make sure CacheMemoryContext exists */
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if (!CacheMemoryContext)
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CreateCacheMemoryContext();
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MemSet(&ctl, 0, sizeof(ctl));
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ctl.keysize = sizeof(Oid);
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ctl.entrysize = sizeof(OpClassCacheEnt);
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OpClassCache = hash_create("Operator class cache", 64,
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&ctl, HASH_ELEM | HASH_BLOBS);
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/* Also make sure CacheMemoryContext exists */
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if (!CacheMemoryContext)
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CreateCacheMemoryContext();
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}
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opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
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@ -1629,16 +1629,10 @@ LookupOpclassInfo(Oid operatorClassOid,
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if (!found)
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{
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/* Need to allocate memory for new entry */
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/* Initialize new entry */
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opcentry->valid = false; /* until known OK */
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opcentry->numSupport = numSupport;
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if (numSupport > 0)
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opcentry->supportProcs = (RegProcedure *)
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MemoryContextAllocZero(CacheMemoryContext,
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numSupport * sizeof(RegProcedure));
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else
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opcentry->supportProcs = NULL;
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opcentry->supportProcs = NULL; /* filled below */
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}
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else
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{
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@ -1646,13 +1640,15 @@ LookupOpclassInfo(Oid operatorClassOid,
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}
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/*
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* When testing for cache-flush hazards, we intentionally disable the
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* operator class cache and force reloading of the info on each call. This
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* is helpful because we want to test the case where a cache flush occurs
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* while we are loading the info, and it's very hard to provoke that if
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* this happens only once per opclass per backend.
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* When aggressively testing cache-flush hazards, we disable the operator
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* class cache and force reloading of the info on each call. This models
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* no real-world behavior, since the cache entries are never invalidated
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* otherwise. However it can be helpful for detecting bugs in the cache
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* loading logic itself, such as reliance on a non-nailed index. Given
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* the limited use-case and the fact that this adds a great deal of
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* expense, we enable it only in CLOBBER_CACHE_RECURSIVELY mode.
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*/
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#if defined(CLOBBER_CACHE_ALWAYS)
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#if defined(CLOBBER_CACHE_RECURSIVELY)
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opcentry->valid = false;
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#endif
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@ -1660,8 +1656,15 @@ LookupOpclassInfo(Oid operatorClassOid,
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return opcentry;
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/*
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* Need to fill in new entry.
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*
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* Need to fill in new entry. First allocate space, unless we already did
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* so in some previous attempt.
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*/
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if (opcentry->supportProcs == NULL && numSupport > 0)
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opcentry->supportProcs = (RegProcedure *)
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MemoryContextAllocZero(CacheMemoryContext,
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numSupport * sizeof(RegProcedure));
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/*
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* To avoid infinite recursion during startup, force heap scans if we're
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* looking up info for the opclasses used by the indexes we would like to
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* reference here.
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