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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2004-05-26 19:44:15 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2004-05-26 19:44:15 +0000 |
| commit | 4646a8f32fbae1581ff0a2fa259bced82fc583e7 (patch) | |
| tree | 89723a25038d1d4506ac3f608df4ee4346e75d0d | |
| parent | 0858ed20d2a3da65de63926c272f80d988a6c58d (diff) | |
| download | postgresql-4646a8f32fbae1581ff0a2fa259bced82fc583e7.tar.gz postgresql-4646a8f32fbae1581ff0a2fa259bced82fc583e7.zip | |
Reduce the minimum allocable chunk size to 8 bytes (from 16). Now that
ListCells are only 8 bytes instead of 12 (on 4-byte-pointer machines
anyway), it's worth maintaining a separate freelist for 8-byte objects.
Remembering that alloc chunks carry 8 bytes of overhead, this should
reduce the net storage requirement for a long List by about a third.
| -rw-r--r-- | src/backend/utils/mmgr/aset.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c index 1a83b2416f4..435b4597083 100644 --- a/src/backend/utils/mmgr/aset.c +++ b/src/backend/utils/mmgr/aset.c @@ -11,7 +11,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.54 2003/11/29 19:52:04 pgsql Exp $ + * $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.55 2004/05/26 19:44:15 tgl Exp $ * * NOTE: * This is a new (Feb. 05, 1999) implementation of the allocation set @@ -85,7 +85,7 @@ * CAUTION: ALLOC_MINBITS must be large enough so that * 1<<ALLOC_MINBITS is at least MAXALIGN, * or we may fail to align the smallest chunks adequately. - * 16-byte alignment is enough on all currently known machines. + * 8-byte alignment is enough on all currently known machines. * * With the current parameters, request sizes up to 8K are treated as chunks, * larger requests go into dedicated blocks. Change ALLOCSET_NUM_FREELISTS @@ -93,8 +93,8 @@ *-------------------- */ -#define ALLOC_MINBITS 4 /* smallest chunk size is 16 bytes */ -#define ALLOCSET_NUM_FREELISTS 10 +#define ALLOC_MINBITS 3 /* smallest chunk size is 8 bytes */ +#define ALLOCSET_NUM_FREELISTS 11 #define ALLOC_CHUNK_LIMIT (1 << (ALLOCSET_NUM_FREELISTS-1+ALLOC_MINBITS)) /* Size of largest chunk that we use a fixed size for */ |