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Improve spinlock code for recent x86 processors: insert a PAUSE

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instruction in the s_lock() wait loop, and use test before test-and-set
in TAS() macro to avoid unnecessary bus traffic.  Patch from Manfred
Spraul, reworked a bit by Tom.
This commit is contained in:
Tom Lane
2003-12-27 20:58:58 +00:00
parent 2cdace962b
commit f8eed65dfb
2 changed files with 27 additions and 2 deletions
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6
src/backend/storage/lmgr/s_lock.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/s_lock.c,v 1.22 2003/12/23 22:15:07 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/s_lock.c,v 1.23 2003/12/27 20:58:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -88,6 +88,10 @@ s_lock(volatile slock_t *lock, const char *file, int line)
while (TAS(lock))
{
/* CPU-specific delay each time through the loop */
SPIN_DELAY();
/* Block the process every SPINS_PER_DELAY tries */
if (++spins > SPINS_PER_DELAY)
{
if (++delays > NUM_DELAYS)