Hi,
Here is the oprofile results of pgbench.
CPU: P4 / Xeon with 2 hyper-threads, speed 2793.55 MHz (estimated)
Counted GLOBAL_POWER_EVENTS events
with a unit mask of 0x01 (mandatory) count 100000
samples % app name symbol name
134521 6.8312 ipmi_si (no symbols)
94515 4.7996 vmlinux schedule
52609 2.6716 postgres AllocSetAlloc
39659 2.0140 postgres base_yyparse
34605 1.7573 vmlinux mwait_idle
33234 1.6877 vmlinux _spin_lock
31353 1.5922 libc-2.3.4.so memcpy
I think that the performance improves if the call frequency of memcpy
is reduced. I measured the place where postgres used memcpy.
(Test program is pgbench -t 4000)
total-size avg-size caller
------------------------------------------------------------------------
636185 111968560 176 catcache.c:1129
68236 18436197 270 xlog.c:947
3909 13822874 3536 xlog.c:940
20003 3520528 176 catcache.c:1376
56010 2071477 36 pgstat.c:2288
125524 1902864 15 dynahash.c:948
20001 1760088 88 setrefs.c:205
catcache.c:1129 is memcpy at SearchCatCache, and catcache.c:1376
is memcpy at SearchCatCacheList.
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
Attached patch is reduce the memcpy calls from SearchCatCache
and SearchCatCacheList. This patch directly uses cache->cc_skey
in looking for hash table.
Here is an effect of the patch.
original: Counted GLOBAL_POWER_EVENTS events
samples % app name symbol name
31353 1.5922 libc-2.3.4.so memcpy
patched: Counted GLOBAL_POWER_EVENTS events
samples % app name symbol name
20629 1.0684 libc-2.3.4.so memcpy
---
Atsushi Ogawa
*** ./src/backend/utils/cache/catcache.c.orig 2009-07-06 22:06:52.000000000
+0900
--- ./src/backend/utils/cache/catcache.c 2009-07-06 13:51:48.000000000
+0900
***************
*** 1124,1140 ****
/*
* initialize the search key information
*/
! memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
! cur_skey[0].sk_argument = v1;
! cur_skey[1].sk_argument = v2;
! cur_skey[2].sk_argument = v3;
! cur_skey[3].sk_argument = v4;
/*
* find the hash bucket in which to look for the tuple
*/
! hashValue = CatalogCacheComputeHashValue(cache, cache->cc_nkeys,
cur_skey);
hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
/*
--- 1124,1141 ----
/*
* initialize the search key information
+ * use cache->cc_skey directly in looking for hash table
*/
! cache->cc_skey[0].sk_argument = v1;
! cache->cc_skey[1].sk_argument = v2;
! cache->cc_skey[2].sk_argument = v3;
! cache->cc_skey[3].sk_argument = v4;
/*
* find the hash bucket in which to look for the tuple
*/
! hashValue = CatalogCacheComputeHashValue(cache, cache->cc_nkeys,
! cache->cc_skey);
hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
/*
***************
*** 1160,1166 ****
HeapKeyTest(&ct->tuple,
cache->cc_tupdesc,
cache->cc_nkeys,
! cur_skey,
res);
if (!res)
continue;
--- 1161,1167 ----
HeapKeyTest(&ct->tuple,
cache->cc_tupdesc,
cache->cc_nkeys,
! cache->cc_skey,
res);
if (!res)
continue;
***************
*** 1222,1227 ****
--- 1223,1234 ----
*/
relation = heap_open(cache->cc_reloid, AccessShareLock);
+ /*
+ * We need copy ScanKey data, because systable_beginscan changes
+ * the ScanKey data.
+ */
+ memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
+
scandesc = systable_beginscan(relation,
cache->cc_indexoid,
IndexScanOK(cache, cur_skey),
***************
*** 1371,1389 ****
/*
* initialize the search key information
*/
! memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
! cur_skey[0].sk_argument = v1;
! cur_skey[1].sk_argument = v2;
! cur_skey[2].sk_argument = v3;
! cur_skey[3].sk_argument = v4;
/*
* compute a hash value of the given keys for faster search. We don't
* presently divide the CatCList items into buckets, but this still lets
* us skip non-matching items quickly most of the time.
*/
! lHashValue = CatalogCacheComputeHashValue(cache, nkeys, cur_skey);
/*
* scan the items until we find a match or exhaust our list
--- 1378,1396 ----
/*
* initialize the search key information
+ * use cache->cc_skey directly in looking for hash table
*/
! cache->cc_skey[0].sk_argument = v1;
! cache->cc_skey[1].sk_argument = v2;
! cache->cc_skey[2].sk_argument = v3;
! cache->cc_skey[3].sk_argument = v4;
/*
* compute a hash value of the given keys for faster search. We don't
* presently divide the CatCList items into buckets, but this still lets
* us skip non-matching items quickly most of the time.
*/
! lHashValue = CatalogCacheComputeHashValue(cache, nkeys, cache->cc_skey);
/*
* scan the items until we find a match or exhaust our list
***************
*** 1410,1416 ****
HeapKeyTest(&cl->tuple,
cache->cc_tupdesc,
nkeys,
! cur_skey,
res);
if (!res)
continue;
--- 1417,1423 ----
HeapKeyTest(&cl->tuple,
cache->cc_tupdesc,
nkeys,
! cache->cc_skey,
res);
if (!res)
continue;
***************
*** 1460,1465 ****
--- 1467,1478 ----
relation = heap_open(cache->cc_reloid, AccessShareLock);
+ /*
+ * We need copy ScanKey data, because systable_beginscan changes
+ * the ScanKey data.
+ */
+ memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
+
scandesc = systable_beginscan(relation,
cache->cc_indexoid,
true,
--
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