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Allow per-tablespace effective_io_concurrency

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Per discussion, nowadays it is possible to have tablespaces that have
wildly different I/O characteristics from others.  Setting different
effective_io_concurrency parameters for those has been measured to
improve performance.

Author: Julien Rouhaud
Reviewed by: Andres Freund
This commit is contained in:
Alvaro Herrera
2015-09-08 12:51:42 -03:00
parent 665a00c9e2
commit 1aba62ec63
12 changed files with 145 additions and 63 deletions
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35
src/backend/executor/nodeBitmapHeapscan.c
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@ -44,6 +44,7 @@
#include "storage/predicate.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/spccache.h"
#include "utils/snapmgr.h"
#include "utils/tqual.h"
@ -95,9 +96,8 @@ BitmapHeapNext(BitmapHeapScanState *node)
* prefetching. node->prefetch_pages tracks exactly how many pages ahead
* the prefetch iterator is. Also, node->prefetch_target tracks the
* desired prefetch distance, which starts small and increases up to the
* GUC-controlled maximum, target_prefetch_pages. This is to avoid doing
* a lot of prefetching in a scan that stops after a few tuples because of
* a LIMIT.
* node->prefetch_maximum. This is to avoid doing a lot of prefetching in
* a scan that stops after a few tuples because of a LIMIT.
*/
if (tbm == NULL)
{
@ -111,7 +111,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
node->tbmres = tbmres = NULL;
#ifdef USE_PREFETCH
if (target_prefetch_pages > 0)
if (node->prefetch_maximum > 0)
{
node->prefetch_iterator = prefetch_iterator = tbm_begin_iterate(tbm);
node->prefetch_pages = 0;
@ -188,10 +188,10 @@ BitmapHeapNext(BitmapHeapScanState *node)
* page/tuple, then to one after the second tuple is fetched, then
* it doubles as later pages are fetched.
*/
if (node->prefetch_target >= target_prefetch_pages)
if (node->prefetch_target >= node->prefetch_maximum)
/* don't increase any further */ ;
else if (node->prefetch_target >= target_prefetch_pages / 2)
node->prefetch_target = target_prefetch_pages;
else if (node->prefetch_target >= node->prefetch_maximum / 2)
node->prefetch_target = node->prefetch_maximum;
else if (node->prefetch_target > 0)
node->prefetch_target *= 2;
else
@ -211,7 +211,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
* Try to prefetch at least a few pages even before we get to the
* second page if we don't stop reading after the first tuple.
*/
if (node->prefetch_target < target_prefetch_pages)
if (node->prefetch_target < node->prefetch_maximum)
node->prefetch_target++;
#endif /* USE_PREFETCH */
}
@ -539,6 +539,7 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
{
BitmapHeapScanState *scanstate;
Relation currentRelation;
int io_concurrency;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@ -564,6 +565,8 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
scanstate->prefetch_iterator = NULL;
scanstate->prefetch_pages = 0;
scanstate->prefetch_target = 0;
/* may be updated below */
scanstate->prefetch_maximum = target_prefetch_pages;
/*
* Miscellaneous initialization
@ -598,6 +601,22 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
/*
* Determine the maximum for prefetch_target. If the tablespace has a
* specific IO concurrency set, use that to compute the corresponding
* maximum value; otherwise, we already initialized to the value computed
* by the GUC machinery.
*/
io_concurrency =
get_tablespace_io_concurrency(currentRelation->rd_rel->reltablespace);
if (io_concurrency != effective_io_concurrency)
{
double maximum;
if (ComputeIoConcurrency(io_concurrency, &maximum))
scanstate->prefetch_maximum = rint(maximum);
}
scanstate->ss.ss_currentRelation = currentRelation;
/*