Dan Ports <d...@csail.mit.edu> wrote:
> On Thu, Mar 31, 2011 at 11:06:30AM -0500, Kevin Grittner wrote:
>> The only thing I've been on the fence about is whether it
>> makes more sense to allocate it all up front or to continue to
allow
>> incremental allocation but set a hard limit on the number of
entries
>> allocated for each shared memory HTAB. Is there a performance-
>> related reason to choose one path or the other?
>
> Seems like it would be marginally better to allocate it up front --
then
> you don't have the cost of having to split buckets later as it
grows.
The attached patch should cover that.
-Kevin
*** a/src/backend/storage/lmgr/lock.c
--- b/src/backend/storage/lmgr/lock.c
***************
*** 281,295 **** InitLocks(void)
{
HASHCTL info;
int hash_flags;
! long init_table_size,
! max_table_size;
/*
* Compute init/max size to request for lock hashtables. Note these
* calculations must agree with LockShmemSize!
*/
max_table_size = NLOCKENTS();
- init_table_size = max_table_size / 2;
/*
* Allocate hash table for LOCK structs. This stores per-locked-object
--- 281,293 ----
{
HASHCTL info;
int hash_flags;
! long max_table_size;
/*
* Compute init/max size to request for lock hashtables. Note these
* calculations must agree with LockShmemSize!
*/
max_table_size = NLOCKENTS();
/*
* Allocate hash table for LOCK structs. This stores per-locked-object
***************
*** 303,316 **** InitLocks(void)
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
LockMethodLockHash = ShmemInitHash("LOCK hash",
!
init_table_size,
max_table_size,
&info,
hash_flags);
/* Assume an average of 2 holders per lock */
max_table_size *= 2;
- init_table_size *= 2;
/*
* Allocate hash table for PROCLOCK structs. This stores
--- 301,313 ----
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
LockMethodLockHash = ShmemInitHash("LOCK hash",
!
max_table_size,
max_table_size,
&info,
hash_flags);
/* Assume an average of 2 holders per lock */
max_table_size *= 2;
/*
* Allocate hash table for PROCLOCK structs. This stores
***************
*** 323,329 **** InitLocks(void)
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
LockMethodProcLockHash = ShmemInitHash("PROCLOCK hash",
!
init_table_size,
max_table_size,
&info,
hash_flags);
--- 320,326 ----
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
LockMethodProcLockHash = ShmemInitHash("PROCLOCK hash",
!
max_table_size,
max_table_size,
&info,
hash_flags);
*** a/src/backend/storage/lmgr/predicate.c
--- b/src/backend/storage/lmgr/predicate.c
***************
*** 959,966 **** InitPredicateLocks(void)
{
HASHCTL info;
int hash_flags;
! long init_table_size,
! max_table_size;
Size requestSize;
bool found;
--- 959,965 ----
{
HASHCTL info;
int hash_flags;
! long max_table_size;
Size requestSize;
bool found;
***************
*** 969,975 **** InitPredicateLocks(void)
* Note these calculations must agree with PredicateLockShmemSize!
*/
max_table_size = NPREDICATELOCKTARGETENTS();
- init_table_size = max_table_size / 2;
/*
* Allocate hash table for PREDICATELOCKTARGET structs. This stores
--- 968,973 ----
***************
*** 983,996 **** InitPredicateLocks(void)
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
PredicateLockTargetHash = ShmemInitHash("PREDICATELOCKTARGET hash",
!
init_table_size,
max_table_size,
&info,
hash_flags);
/* Assume an average of 2 xacts per target */
max_table_size *= 2;
- init_table_size *= 2;
/*
* Reserve an entry in the hash table; we use it to make sure there's
--- 981,993 ----
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
PredicateLockTargetHash = ShmemInitHash("PREDICATELOCKTARGET hash",
!
max_table_size,
max_table_size,
&info,
hash_flags);
/* Assume an average of 2 xacts per target */
max_table_size *= 2;
/*
* Reserve an entry in the hash table; we use it to make sure there's
***************
*** 1014,1020 **** InitPredicateLocks(void)
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
PredicateLockHash = ShmemInitHash("PREDICATELOCK hash",
!
init_table_size,
max_table_size,
&info,
hash_flags);
--- 1011,1017 ----
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
PredicateLockHash = ShmemInitHash("PREDICATELOCK hash",
!
max_table_size,
max_table_size,
&info,
hash_flags);
--
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