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Get rid of slru.c's hardwired insistence on a fixed number of slots per
SLRU area. The number of slots is still a compile-time constant (someday we might want to change that), but at least it's a different constant for each SLRU area. Increase number of subtrans buffers to 32 based on experimentation with a heavily subtrans-bashing test case, and increase number of multixact member buffers to 16, since it's obviously silly for it not to be at least twice the number of multixact offset buffers.
1 parent 3001b46 commit 887a7c6

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9 files changed

+118
-65
lines changed

9 files changed

+118
-65
lines changed

‎src/backend/access/transam/clog.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,7 @@
2424
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
2525
* Portions Copyright (c) 1994, Regents of the University of California
2626
*
27-
* $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.35 2005/12/06 18:10:06 tgl Exp $
27+
* $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.36 2005/12/06 23:08:32 tgl Exp $
2828
*
2929
*-------------------------------------------------------------------------
3030
*/
@@ -147,14 +147,15 @@ TransactionIdGetStatus(TransactionId xid)
147147
Size
148148
CLOGShmemSize(void)
149149
{
150-
return SimpleLruShmemSize();
150+
return SimpleLruShmemSize(NUM_CLOG_BUFFERS);
151151
}
152152

153153
void
154154
CLOGShmemInit(void)
155155
{
156156
ClogCtl->PagePrecedes = CLOGPagePrecedes;
157-
SimpleLruInit(ClogCtl, "CLOG Ctl", CLogControlLock, "pg_clog");
157+
SimpleLruInit(ClogCtl, "CLOG Ctl", NUM_CLOG_BUFFERS,
158+
CLogControlLock, "pg_clog");
158159
}
159160

160161
/*

‎src/backend/access/transam/multixact.c

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -42,7 +42,7 @@
4242
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
4343
* Portions Copyright (c) 1994, Regents of the University of California
4444
*
45-
* $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.14 2005/12/06 18:10:06 tgl Exp $
45+
* $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.15 2005/12/06 23:08:32 tgl Exp $
4646
*
4747
*-------------------------------------------------------------------------
4848
*/
@@ -1249,8 +1249,8 @@ MultiXactShmemSize(void)
12491249
mul_size(sizeof(MultiXactId) * 2, MaxBackends))
12501250

12511251
size = SHARED_MULTIXACT_STATE_SIZE;
1252-
size = add_size(size, SimpleLruShmemSize());
1253-
size = add_size(size, SimpleLruShmemSize());
1252+
size = add_size(size, SimpleLruShmemSize(NUM_MXACTOFFSET_BUFFERS));
1253+
size = add_size(size, SimpleLruShmemSize(NUM_MXACTMEMBER_BUFFERS));
12541254

12551255
return size;
12561256
}
@@ -1265,9 +1265,11 @@ MultiXactShmemInit(void)
12651265
MultiXactOffsetCtl->PagePrecedes = MultiXactOffsetPagePrecedes;
12661266
MultiXactMemberCtl->PagePrecedes = MultiXactMemberPagePrecedes;
12671267

1268-
SimpleLruInit(MultiXactOffsetCtl, "MultiXactOffset Ctl",
1268+
SimpleLruInit(MultiXactOffsetCtl,
1269+
"MultiXactOffset Ctl", NUM_MXACTOFFSET_BUFFERS,
12691270
MultiXactOffsetControlLock, "pg_multixact/offsets");
1270-
SimpleLruInit(MultiXactMemberCtl, "MultiXactMember Ctl",
1271+
SimpleLruInit(MultiXactMemberCtl,
1272+
"MultiXactMember Ctl", NUM_MXACTMEMBER_BUFFERS,
12711273
MultiXactMemberControlLock, "pg_multixact/members");
12721274

12731275
/* Initialize our shared state struct */

‎src/backend/access/transam/slru.c

Lines changed: 68 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -41,7 +41,7 @@
4141
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
4242
* Portions Copyright (c) 1994, Regents of the University of California
4343
*
44-
* $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.32 2005/12/06 18:10:06 tgl Exp $
44+
* $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.33 2005/12/06 23:08:32 tgl Exp $
4545
*
4646
*-------------------------------------------------------------------------
4747
*/
@@ -87,11 +87,13 @@
8787
* until control returns to SimpleLruFlush(). This data structure remembers
8888
* which files are open.
8989
*/
90+
#define MAX_FLUSH_BUFFERS 16
91+
9092
typedef struct SlruFlushData
9193
{
92-
int num_files; /* # files actually open */
93-
int fd[NUM_SLRU_BUFFERS]; /* their FD's */
94-
int segno[NUM_SLRU_BUFFERS]; /* their log seg#s */
94+
int num_files; /* # files actually open */
95+
int fd[MAX_FLUSH_BUFFERS]; /* their FD's */
96+
int segno[MAX_FLUSH_BUFFERS]; /* their log seg#s */
9597
} SlruFlushData;
9698

9799
/*
@@ -150,25 +152,38 @@ static int SlruSelectLRUPage(SlruCtl ctl, int pageno);
150152
*/
151153

152154
Size
153-
SimpleLruShmemSize(void)
155+
SimpleLruShmemSize(int nslots)
154156
{
155-
/* we assume NUM_SLRU_BUFFERS isn't so large as to risk overflow */
156-
return BUFFERALIGN(sizeof(SlruSharedData)) + BLCKSZ * NUM_SLRU_BUFFERS;
157+
Size sz;
158+
159+
/* we assume nslots isn't so large as to risk overflow */
160+
sz = MAXALIGN(sizeof(SlruSharedData));
161+
sz += MAXALIGN(nslots * sizeof(char *)); /* page_buffer[] */
162+
sz += MAXALIGN(nslots * sizeof(SlruPageStatus)); /* page_status[] */
163+
sz += MAXALIGN(nslots * sizeof(bool)); /* page_dirty[] */
164+
sz += MAXALIGN(nslots * sizeof(int)); /* page_number[] */
165+
sz += MAXALIGN(nslots * sizeof(int)); /* page_lru_count[] */
166+
sz += MAXALIGN(nslots * sizeof(LWLockId)); /* buffer_locks[] */
167+
168+
return BUFFERALIGN(sz) + BLCKSZ * nslots;
157169
}
158170

159171
void
160-
SimpleLruInit(SlruCtl ctl, const char *name,
172+
SimpleLruInit(SlruCtl ctl, const char *name, int nslots,
161173
LWLockId ctllock, const char *subdir)
162174
{
163175
SlruShared shared;
164176
bool found;
165177

166-
shared = (SlruShared) ShmemInitStruct(name, SimpleLruShmemSize(), &found);
178+
shared = (SlruShared) ShmemInitStruct(name,
179+
SimpleLruShmemSize(nslots),
180+
&found);
167181

168182
if (!IsUnderPostmaster)
169183
{
170184
/* Initialize locks and shared memory area */
171-
char *bufptr;
185+
char *ptr;
186+
Size offset;
172187
int slotno;
173188

174189
Assert(!found);
@@ -177,19 +192,37 @@ SimpleLruInit(SlruCtl ctl, const char *name,
177192

178193
shared->ControlLock = ctllock;
179194

180-
bufptr = (char *) shared + BUFFERALIGN(sizeof(SlruSharedData));
195+
shared->num_slots = nslots;
196+
197+
shared->cur_lru_count = 0;
198+
199+
/* shared->latest_page_number will be set later */
181200

182-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
201+
ptr = (char *) shared;
202+
offset = MAXALIGN(sizeof(SlruSharedData));
203+
shared->page_buffer = (char **) (ptr + offset);
204+
offset += MAXALIGN(nslots * sizeof(char *));
205+
shared->page_status = (SlruPageStatus *) (ptr + offset);
206+
offset += MAXALIGN(nslots * sizeof(SlruPageStatus));
207+
shared->page_dirty = (bool *) (ptr + offset);
208+
offset += MAXALIGN(nslots * sizeof(bool));
209+
shared->page_number = (int *) (ptr + offset);
210+
offset += MAXALIGN(nslots * sizeof(int));
211+
shared->page_lru_count = (int *) (ptr + offset);
212+
offset += MAXALIGN(nslots * sizeof(int));
213+
shared->buffer_locks = (LWLockId *) (ptr + offset);
214+
offset += MAXALIGN(nslots * sizeof(LWLockId));
215+
ptr += BUFFERALIGN(offset);
216+
217+
for (slotno = 0; slotno < nslots; slotno++)
183218
{
184-
shared->page_buffer[slotno] = bufptr;
219+
shared->page_buffer[slotno] = ptr;
185220
shared->page_status[slotno] = SLRU_PAGE_EMPTY;
186221
shared->page_dirty[slotno] = false;
187222
shared->page_lru_count[slotno] = 0;
188223
shared->buffer_locks[slotno] = LWLockAssign();
189-
bufptr += BLCKSZ;
224+
ptr += BLCKSZ;
190225
}
191-
192-
/* shared->latest_page_number will be set later */
193226
}
194227
else
195228
Assert(found);
@@ -394,7 +427,7 @@ SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno, TransactionId xid)
394427
LWLockAcquire(shared->ControlLock, LW_SHARED);
395428

396429
/* See if page is already in a buffer */
397-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
430+
for (slotno = 0; slotno < shared->num_slots; slotno++)
398431
{
399432
if (shared->page_number[slotno] == pageno &&
400433
shared->page_status[slotno] != SLRU_PAGE_EMPTY &&
@@ -643,9 +676,20 @@ SlruPhysicalWritePage(SlruCtl ctl, int pageno, int slotno, SlruFlush fdata)
643676

644677
if (fdata)
645678
{
646-
fdata->fd[fdata->num_files] = fd;
647-
fdata->segno[fdata->num_files] = segno;
648-
fdata->num_files++;
679+
if (fdata->num_files < MAX_FLUSH_BUFFERS)
680+
{
681+
fdata->fd[fdata->num_files] = fd;
682+
fdata->segno[fdata->num_files] = segno;
683+
fdata->num_files++;
684+
}
685+
else
686+
{
687+
/*
688+
* In the unlikely event that we exceed MAX_FLUSH_BUFFERS,
689+
* fall back to treating it as a standalone write.
690+
*/
691+
fdata = NULL;
692+
}
649693
}
650694
}
651695

@@ -797,7 +841,7 @@ SlruSelectLRUPage(SlruCtl ctl, int pageno)
797841
int best_page_number;
798842

799843
/* See if page already has a buffer assigned */
800-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
844+
for (slotno = 0; slotno < shared->num_slots; slotno++)
801845
{
802846
if (shared->page_number[slotno] == pageno &&
803847
shared->page_status[slotno] != SLRU_PAGE_EMPTY)
@@ -830,7 +874,7 @@ SlruSelectLRUPage(SlruCtl ctl, int pageno)
830874
best_delta = -1;
831875
bestslot = 0; /* no-op, just keeps compiler quiet */
832876
best_page_number = 0; /* ditto */
833-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
877+
for (slotno = 0; slotno < shared->num_slots; slotno++)
834878
{
835879
int this_delta;
836880
int this_page_number;
@@ -908,7 +952,7 @@ SimpleLruFlush(SlruCtl ctl, bool checkpoint)
908952

909953
LWLockAcquire(shared->ControlLock, LW_EXCLUSIVE);
910954

911-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
955+
for (slotno = 0; slotno < shared->num_slots; slotno++)
912956
{
913957
SimpleLruWritePage(ctl, slotno, &fdata);
914958

@@ -990,7 +1034,7 @@ restart:;
9901034
return;
9911035
}
9921036

993-
for (slotno = 0; slotno < NUM_SLRU_BUFFERS; slotno++)
1037+
for (slotno = 0; slotno < shared->num_slots; slotno++)
9941038
{
9951039
if (shared->page_status[slotno] == SLRU_PAGE_EMPTY)
9961040
continue;

‎src/backend/access/transam/subtrans.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -22,7 +22,7 @@
2222
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
2323
* Portions Copyright (c) 1994, Regents of the University of California
2424
*
25-
* $PostgreSQL: pgsql/src/backend/access/transam/subtrans.c,v 1.14 2005/12/06 18:10:06 tgl Exp $
25+
* $PostgreSQL: pgsql/src/backend/access/transam/subtrans.c,v 1.15 2005/12/06 23:08:32 tgl Exp $
2626
*
2727
*-------------------------------------------------------------------------
2828
*/
@@ -164,14 +164,14 @@ SubTransGetTopmostTransaction(TransactionId xid)
164164
Size
165165
SUBTRANSShmemSize(void)
166166
{
167-
return SimpleLruShmemSize();
167+
return SimpleLruShmemSize(NUM_SUBTRANS_BUFFERS);
168168
}
169169

170170
void
171171
SUBTRANSShmemInit(void)
172172
{
173173
SubTransCtl->PagePrecedes = SubTransPagePrecedes;
174-
SimpleLruInit(SubTransCtl, "SUBTRANS Ctl",
174+
SimpleLruInit(SubTransCtl, "SUBTRANS Ctl", NUM_SUBTRANS_BUFFERS,
175175
SubtransControlLock, "pg_subtrans");
176176
/* Override default assumption that writes should be fsync'd */
177177
SubTransCtl->do_fsync = false;

‎src/backend/storage/lmgr/lwlock.c

Lines changed: 8 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -15,13 +15,15 @@
1515
* Portions Copyright (c) 1994, Regents of the University of California
1616
*
1717
* IDENTIFICATION
18-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.34 2005/10/15 02:49:26 momjian Exp $
18+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.35 2005/12/06 23:08:33 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
2222
#include "postgres.h"
2323

24-
#include "access/slru.h"
24+
#include "access/clog.h"
25+
#include "access/multixact.h"
26+
#include "access/subtrans.h"
2527
#include "storage/lwlock.h"
2628
#include "storage/proc.h"
2729
#include "storage/spin.h"
@@ -129,16 +131,13 @@ NumLWLocks(void)
129131
numLocks += 2 * NBuffers;
130132

131133
/* clog.c needs one per CLOG buffer */
132-
numLocks += NUM_SLRU_BUFFERS;
134+
numLocks += NUM_CLOG_BUFFERS;
133135

134136
/* subtrans.c needs one per SubTrans buffer */
135-
numLocks += NUM_SLRU_BUFFERS;
137+
numLocks += NUM_SUBTRANS_BUFFERS;
136138

137-
/*
138-
* multixact.c needs one per MultiXact buffer, but there are two SLRU
139-
* areas for MultiXact
140-
*/
141-
numLocks += 2 * NUM_SLRU_BUFFERS;
139+
/* multixact.c needs two SLRU areas */
140+
numLocks += NUM_MXACTOFFSET_BUFFERS + NUM_MXACTMEMBER_BUFFERS;
142141

143142
/* Leave a few extra for use by user-defined modules. */
144143
numLocks += NUM_USER_DEFINED_LWLOCKS;

‎src/include/access/clog.h

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $PostgreSQL: pgsql/src/include/access/clog.h,v 1.14 2005/08/20 23:26:29 tgl Exp $
9+
* $PostgreSQL: pgsql/src/include/access/clog.h,v 1.15 2005/12/06 23:08:34 tgl Exp $
1010
*/
1111
#ifndef CLOG_H
1212
#define CLOG_H
@@ -28,6 +28,10 @@ typedef int XidStatus;
2828
#define TRANSACTION_STATUS_SUB_COMMITTED 0x03
2929

3030

31+
/* Number of SLRU buffers to use for clog */
32+
#define NUM_CLOG_BUFFERS 8
33+
34+
3135
extern void TransactionIdSetStatus(TransactionId xid, XidStatus status);
3236
extern XidStatus TransactionIdGetStatus(TransactionId xid);
3337

‎src/include/access/multixact.h

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.7 2005/10/15 02:49:42 momjian Exp $
9+
* $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.8 2005/12/06 23:08:34 tgl Exp $
1010
*/
1111
#ifndef MULTIXACT_H
1212
#define MULTIXACT_H
@@ -18,6 +18,10 @@
1818

1919
#define MultiXactIdIsValid(multi) ((multi) != InvalidMultiXactId)
2020

21+
/* Number of SLRU buffers to use for multixact */
22+
#define NUM_MXACTOFFSET_BUFFERS 8
23+
#define NUM_MXACTMEMBER_BUFFERS 16
24+
2125
/* ----------------
2226
* multixact-related XLOG entries
2327
* ----------------

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