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Commite1a7772

Browse files
author
Alexander Korotkov
committed
Implement double buffering.
1 parente5863bc commite1a7772

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3 files changed

+57
-27
lines changed

3 files changed

+57
-27
lines changed

‎contrib/pg_stat_wait/collector.c‎

Lines changed: 25 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -61,18 +61,35 @@ AllocHistory(History *observations, int count)
6161
void
6262
ReadCurrentWait(PGPROC*proc,HistoryItem*item)
6363
{
64-
CurrentWaitEvent*wait;
65-
instr_timecurrentTime;
64+
instr_timestartTime,currentTime;
6665

67-
wait=&cur_wait_events[proc->pgprocno];
66+
while (true)
67+
{
68+
CurrentWaitEventWrap*wrap;
69+
CurrentWaitEvent*event;
70+
uint32previdx;
71+
72+
73+
wrap=&cur_wait_events[proc->pgprocno];
74+
previdx=wrap->curidx;
75+
event=&wrap->data[(previdx+1) %2];
76+
77+
pg_read_barrier();
6878

69-
item->backendPid=proc->pid;
70-
item->classid=wait->classid;
71-
item->eventid=wait->eventid;
72-
memcpy(item->params,wait->params,sizeof(item->params));
79+
item->backendPid=proc->pid;
80+
item->classid=event->classeventid >>16;
81+
item->eventid=event->classeventid&0xFFFF;
82+
memcpy(item->params,event->params,sizeof(event->params));
83+
startTime=event->start_time;
84+
85+
pg_read_barrier();
86+
87+
if (wrap->curidx==previdx)
88+
break;
89+
}
7390

7491
INSTR_TIME_SET_CURRENT(currentTime);
75-
INSTR_TIME_SUBTRACT(currentTime,wait->start_time);
92+
INSTR_TIME_SUBTRACT(currentTime,startTime);
7693
item->waitTime=INSTR_TIME_GET_MICROSEC(currentTime);
7794
}
7895

‎contrib/pg_stat_wait/pg_stat_wait.c‎

Lines changed: 24 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,7 @@ boolhistorySkipLatch;
2828
shm_toc*toc=NULL;
2929
CollectorShmqHeader*collector_hdr=NULL;
3030
shm_mq*collector_mq=NULL;
31-
CurrentWaitEvent*cur_wait_events=NULL;
31+
CurrentWaitEventWrap*cur_wait_events=NULL;
3232

3333
staticintmaxProcs;
3434

@@ -53,7 +53,7 @@ pgsw_shmem_size(void)
5353

5454
shm_toc_initialize_estimator(&e);
5555

56-
shm_toc_estimate_chunk(&e,sizeof(CurrentWaitEvent)*maxProcs);
56+
shm_toc_estimate_chunk(&e,sizeof(CurrentWaitEventWrap)*maxProcs);
5757
nkeys=1;
5858

5959
if (waitsHistoryOn)
@@ -85,7 +85,7 @@ pgsw_shmem_startup(void)
8585
{
8686
toc=shm_toc_create(PG_STAT_WAIT_MAGIC,pgsw,segsize);
8787

88-
cur_wait_events=shm_toc_allocate(toc,sizeof(CurrentWaitEvent)*maxProcs);
88+
cur_wait_events=shm_toc_allocate(toc,sizeof(CurrentWaitEventWrap)*maxProcs);
8989
shm_toc_insert(toc,0,cur_wait_events);
9090

9191
if (waitsHistoryOn)
@@ -122,22 +122,26 @@ static void
122122
pgsw_wait_event_start_hook(uint32classid,uint32eventid,
123123
uint32p1,uint32p2,uint32p3,uint32p4,uint32p5)
124124
{
125-
CurrentWaitEvent*event;
125+
CurrentWaitEventWrap*wrap;
126+
CurrentWaitEvent*event;
126127

127128
if (!shmem_initialized|| !MyProc)
128129
return;
129130

130-
event=&cur_wait_events[MyProc->pgprocno];
131+
wrap=&cur_wait_events[MyProc->pgprocno];
132+
event=&wrap->data[(wrap->curidx+1) %2];
131133

132-
event->classid=classid;
133-
event->eventid=eventid;
134-
event->params[0]=0;
135-
event->params[1]=0;
136-
event->params[2]=0;
137-
event->params[3]=0;
138-
event->params[4]=0;
134+
event->classeventid= (classid <<16) |eventid;
135+
event->params[0]=p1;
136+
event->params[1]=p2;
137+
event->params[2]=p3;
138+
event->params[3]=p4;
139+
event->params[4]=p5;
139140
INSTR_TIME_SET_CURRENT(event->start_time);
140141

142+
pg_write_barrier();
143+
wrap->curidx++;
144+
141145
if (prev_wait_event_start_hook)
142146
prev_wait_event_start_hook(classid,eventid,p1,p2,p3,p4,p5);
143147
}
@@ -148,22 +152,26 @@ pgsw_wait_event_start_hook(uint32 classid, uint32 eventid,
148152
staticvoid
149153
pgsw_wait_event_stop_hook(void)
150154
{
151-
CurrentWaitEvent*event;
155+
CurrentWaitEventWrap*wrap;
156+
CurrentWaitEvent*event;
152157

153158
if (!shmem_initialized|| !MyProc)
154159
return;
155160

156-
event=&cur_wait_events[MyProc->pgprocno];
161+
wrap=&cur_wait_events[MyProc->pgprocno];
162+
event=&wrap->data[(wrap->curidx+1) %2];
157163

158-
event->classid=WAIT_CPU;
159-
event->eventid=WAIT_CPU_BUSY;
164+
event->classeventid= (WAIT_CPU <<16) |WAIT_CPU_BUSY;
160165
event->params[0]=0;
161166
event->params[1]=0;
162167
event->params[2]=0;
163168
event->params[3]=0;
164169
event->params[4]=0;
165170
INSTR_TIME_SET_CURRENT(event->start_time);
166171

172+
pg_write_barrier();
173+
wrap->curidx++;
174+
167175
if (prev_wait_event_stop_hook)
168176
prev_wait_event_stop_hook();
169177
}

‎contrib/pg_stat_wait/pg_stat_wait.h‎

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -15,12 +15,17 @@
1515

1616
typedefstruct
1717
{
18-
uint32classid;
19-
uint32eventid;
18+
uint32classeventid;
2019
uint32params[WAIT_PARAMS_COUNT];
2120
instr_timestart_time;
2221
}CurrentWaitEvent;
2322

23+
typedefstruct
24+
{
25+
uint32curidx;
26+
CurrentWaitEventdata[2];
27+
}CurrentWaitEventWrap;
28+
2429
typedefstruct
2530
{
2631
uint32backendPid;
@@ -79,7 +84,7 @@ typedef struct
7984
/* pg_stat_wait.c */
8085
externvoidcheck_shmem(void);
8186
externCollectorShmqHeader*collector_hdr;
82-
externCurrentWaitEvent*cur_wait_events;
87+
externCurrentWaitEventWrap*cur_wait_events;
8388
externshm_mq*collector_mq;
8489
externinthistorySize;
8590
externinthistoryPeriod;

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