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Convert the PGPROC->lwWaitLink list into a dlist instead of open coding it.

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Besides being shorter and much easier to read it changes the logic in
LWLockRelease() to release all shared lockers when waking up any. This
can yield some significant performance improvements - and the fairness
isn't really much worse than before, as we always allowed new shared
lockers to jump the queue.
This commit is contained in:
Andres Freund
2014-12-25 17:24:30 +01:00
parent 570bd2b3fd
commit 7882c3b0b9
5 changed files with 58 additions and 101 deletions
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5
src/include/storage/lwlock.h
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@@ -14,6 +14,7 @@
#ifndef LWLOCK_H
#define LWLOCK_H
#include "lib/ilist.h"
#include "storage/s_lock.h"
struct PGPROC;
@@ -50,9 +51,7 @@ typedef struct LWLock
char exclusive; /* # of exclusive holders (0 or 1) */
int shared; /* # of shared holders (0..MaxBackends) */
int tranche; /* tranche ID */
struct PGPROC *head; /* head of list of waiting PGPROCs */
struct PGPROC *tail; /* tail of list of waiting PGPROCs */
/* tail is undefined when head is NULL */
dlist_head waiters; /* list of waiting PGPROCs */
} LWLock;
/*

3
src/include/storage/proc.h
View File

@@ -15,6 +15,7 @@
#define _PROC_H_
#include "access/xlogdefs.h"
#include "lib/ilist.h"
#include "storage/latch.h"
#include "storage/lock.h"
#include "storage/pg_sema.h"
@@ -104,7 +105,7 @@ struct PGPROC
/* Info about LWLock the process is currently waiting for, if any. */
bool lwWaiting; /* true if waiting for an LW lock */
uint8 lwWaitMode; /* lwlock mode being waited for */
struct PGPROC *lwWaitLink; /* next waiter for same LW lock */
dlist_node lwWaitLink; /* position in LW lock wait list */
/* Info about lock the process is currently waiting for, if any. */
/* waitLock and waitProcLock are NULL if not currently waiting. */