static uint64
test_timing(int32 duration)
{
uint64 total_time;
int64 time_elapsed = 0;
uint64 loop_count = 0;
uint64 prev,
cur;
instr_time start_time,
end_time,
temp;
total_time = duration > 0 ? duration * 1000000 : 0;
INSTR_TIME_SET_CURRENT(start_time);
cur = INSTR_TIME_GET_MICROSEC(start_time);
while (time_elapsed < total_time)
{
int32 diff,
bits = 0;
prev = cur;
INSTR_TIME_SET_CURRENT(temp);
cur = INSTR_TIME_GET_MICROSEC(temp);
diff = cur - prev;
/* Did time go backwards? */
if (diff < 0)
{
printf("Detected clock going backwards in time.\n");
printf("Time warp: %d microseconds\n", diff);
exit(1);
}
/* What is the highest bit in the time diff? */
while (diff)
{
diff >>= 1;
bits++;
}
/* Update appropriate duration bucket */
histogram[bits]++;
loop_count++;
INSTR_TIME_SUBTRACT(temp, start_time);
time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
}
INSTR_TIME_SET_CURRENT(end_time);
INSTR_TIME_SUBTRACT(end_time, start_time);
printf("Per loop time including overhead: %0.2f nsec\n",
INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
return loop_count;
}
Datum
pg_stat_get_xact_function_self_time(PG_FUNCTION_ARGS)
{
Oid funcid = PG_GETARG_OID(0);
PgStat_BackendFunctionEntry *funcentry;
if ((funcentry = find_funcstat_entry(funcid)) == NULL)
PG_RETURN_NULL();
PG_RETURN_INT64(INSTR_TIME_GET_MICROSEC(funcentry->f_counts.f_time_self));
}
/*
* Rescan end pages to verify that they are (still) empty of tuples.
*
* Returns number of nondeletable pages (last nonempty page + 1).
*/
static BlockNumber
count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
{
BlockNumber blkno;
instr_time starttime;
instr_time currenttime;
instr_time elapsed;
/* Initialize the starttime if we check for conflicting lock requests */
INSTR_TIME_SET_CURRENT(starttime);
/* Strange coding of loop control is needed because blkno is unsigned */
blkno = vacrelstats->rel_pages;
while (blkno > vacrelstats->nonempty_pages)
{
Buffer buf;
Page page;
OffsetNumber offnum,
maxoff;
bool hastup;
/*
* Check if another process requests a lock on our relation. We are
* holding an AccessExclusiveLock here, so they will be waiting. We
* only do this in autovacuum_truncate_lock_check millisecond
* intervals, and we only check if that interval has elapsed once
* every 32 blocks to keep the number of system calls and actual
* shared lock table lookups to a minimum.
*/
if ((blkno % 32) == 0)
{
INSTR_TIME_SET_CURRENT(currenttime);
elapsed = currenttime;
INSTR_TIME_SUBTRACT(elapsed, starttime);
if ((INSTR_TIME_GET_MICROSEC(elapsed) / 1000)
>= AUTOVACUUM_TRUNCATE_LOCK_CHECK_INTERVAL)
{
if (LockHasWaitersRelation(onerel, AccessExclusiveLock))
{
ereport(elevel,
(errmsg("\"%s\": suspending truncate "
"due to conflicting lock request",
RelationGetRelationName(onerel))));
vacrelstats->lock_waiter_detected = true;
return blkno;
}
starttime = currenttime;
}
}
/*
* We don't insert a vacuum delay point here, because we have an
* exclusive lock on the table which we want to hold for as short a
* time as possible. We still need to check for interrupts however.
*/
CHECK_FOR_INTERRUPTS();
blkno--;
buf = ReadBufferExtended(onerel, MAIN_FORKNUM, blkno,
RBM_NORMAL, vac_strategy);
/* In this phase we only need shared access to the buffer */
LockBuffer(buf, BUFFER_LOCK_SHARE);
page = BufferGetPage(buf);
if (PageIsNew(page) || PageIsEmpty(page))
{
/* PageIsNew probably shouldn't happen... */
UnlockReleaseBuffer(buf);
continue;
}
hastup = false;
maxoff = PageGetMaxOffsetNumber(page);
for (offnum = FirstOffsetNumber;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
ItemId itemid;
itemid = PageGetItemId(page, offnum);
/*
* Note: any non-unused item should be taken as a reason to keep
* this page. We formerly thought that DEAD tuples could be
* thrown away, but that's not so, because we'd not have cleaned
* out their index entries.
*/
if (ItemIdIsUsed(itemid))
{
hastup = true;
break; /* can stop scanning */
}
} /* scan along page */
UnlockReleaseBuffer(buf);
/* Done scanning if we found a tuple here */
if (hastup)
return blkno + 1;
}
/*
* If we fall out of the loop, all the previously-thought-to-be-empty
* pages still are; we need not bother to look at the last known-nonempty
* page.
*/
return vacrelstats->nonempty_pages;
}
