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Commitbb952c8

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Allow specifying initial and maximum segment sizes for DSA.
Previously, the DSA segment size always started with 1MB and grew upto DSA_MAX_SEGMENT_SIZE. It was inconvenient in certain scenarios,such as when the caller desired a soft constraint on the total DSAsegment size, limiting it to less than 1MB.This commit introduces the capability to specify the initial andmaximum DSA segment sizes when creating a DSA area, providing moreflexibility and control over memory usage.Reviewed-by: John Naylor, Tomas VondraDiscussion:https://postgr.es/m/CAD21AoAYGGC1ePjVX0H%2Bpp9rH%3D9vuPK19nNOiu12NprdV5TVJA%40mail.gmail.com
1 parent1f42337 commitbb952c8

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2 files changed

+71
-38
lines changed

2 files changed

+71
-38
lines changed

‎src/backend/utils/mmgr/dsa.c

Lines changed: 29 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -59,14 +59,6 @@
5959
#include"utils/memutils.h"
6060
#include"utils/resowner.h"
6161

62-
/*
63-
* The size of the initial DSM segment that backs a dsa_area created by
64-
* dsa_create. After creating some number of segments of this size we'll
65-
* double this size, and so on. Larger segments may be created if necessary
66-
* to satisfy large requests.
67-
*/
68-
#defineDSA_INITIAL_SEGMENT_SIZE ((size_t) (1 * 1024 * 1024))
69-
7062
/*
7163
* How many segments to create before we double the segment size. If this is
7264
* low, then there is likely to be a lot of wasted space in the largest
@@ -76,17 +68,6 @@
7668
*/
7769
#defineDSA_NUM_SEGMENTS_AT_EACH_SIZE 2
7870

79-
/*
80-
* The number of bits used to represent the offset part of a dsa_pointer.
81-
* This controls the maximum size of a segment, the maximum possible
82-
* allocation size and also the maximum number of segments per area.
83-
*/
84-
#ifSIZEOF_DSA_POINTER==4
85-
#defineDSA_OFFSET_WIDTH 27/* 32 segments of size up to 128MB */
86-
#else
87-
#defineDSA_OFFSET_WIDTH 40/* 1024 segments of size up to 1TB */
88-
#endif
89-
9071
/*
9172
* The maximum number of DSM segments that an area can own, determined by
9273
* the number of bits remaining (but capped at 1024).
@@ -97,9 +78,6 @@
9778
/* The bitmask for extracting the offset from a dsa_pointer. */
9879
#defineDSA_OFFSET_BITMASK (((dsa_pointer) 1 << DSA_OFFSET_WIDTH) - 1)
9980

100-
/* The maximum size of a DSM segment. */
101-
#defineDSA_MAX_SEGMENT_SIZE ((size_t) 1 << DSA_OFFSET_WIDTH)
102-
10381
/* Number of pages (see FPM_PAGE_SIZE) per regular superblock. */
10482
#defineDSA_PAGES_PER_SUPERBLOCK16
10583

@@ -318,6 +296,10 @@ typedef struct
318296
dsa_segment_indexsegment_bins[DSA_NUM_SEGMENT_BINS];
319297
/* The object pools for each size class. */
320298
dsa_area_poolpools[DSA_NUM_SIZE_CLASSES];
299+
/* initial allocation segment size */
300+
size_tinit_segment_size;
301+
/* maximum allocation segment size */
302+
size_tmax_segment_size;
321303
/* The total size of all active segments. */
322304
size_ttotal_segment_size;
323305
/* The maximum total size of backing storage we are allowed. */
@@ -417,7 +399,9 @@ static dsa_segment_map *make_new_segment(dsa_area *area, size_t requested_pages)
417399
staticdsa_area*create_internal(void*place,size_tsize,
418400
inttranche_id,
419401
dsm_handlecontrol_handle,
420-
dsm_segment*control_segment);
402+
dsm_segment*control_segment,
403+
size_tinit_segment_size,
404+
size_tmax_segment_size);
421405
staticdsa_area*attach_internal(void*place,dsm_segment*segment,
422406
dsa_handlehandle);
423407
staticvoidcheck_for_freed_segments(dsa_area*area);
@@ -434,7 +418,7 @@ static void rebin_segment(dsa_area *area, dsa_segment_map *segment_map);
434418
* we require the caller to provide one.
435419
*/
436420
dsa_area*
437-
dsa_create(inttranche_id)
421+
dsa_create_ext(inttranche_id,size_tinit_segment_size,size_tmax_segment_size)
438422
{
439423
dsm_segment*segment;
440424
dsa_area*area;
@@ -443,7 +427,7 @@ dsa_create(int tranche_id)
443427
* Create the DSM segment that will hold the shared control object and the
444428
* first segment of usable space.
445429
*/
446-
segment=dsm_create(DSA_INITIAL_SEGMENT_SIZE,0);
430+
segment=dsm_create(init_segment_size,0);
447431

448432
/*
449433
* All segments backing this area are pinned, so that DSA can explicitly
@@ -455,9 +439,10 @@ dsa_create(int tranche_id)
455439

456440
/* Create a new DSA area with the control object in this segment. */
457441
area=create_internal(dsm_segment_address(segment),
458-
DSA_INITIAL_SEGMENT_SIZE,
442+
init_segment_size,
459443
tranche_id,
460-
dsm_segment_handle(segment),segment);
444+
dsm_segment_handle(segment),segment,
445+
init_segment_size,max_segment_size);
461446

462447
/* Clean up when the control segment detaches. */
463448
on_dsm_detach(segment,&dsa_on_dsm_detach_release_in_place,
@@ -483,13 +468,15 @@ dsa_create(int tranche_id)
483468
* See dsa_create() for a note about the tranche arguments.
484469
*/
485470
dsa_area*
486-
dsa_create_in_place(void*place,size_tsize,
487-
inttranche_id,dsm_segment*segment)
471+
dsa_create_in_place_ext(void*place,size_tsize,
472+
inttranche_id,dsm_segment*segment,
473+
size_tinit_segment_size,size_tmax_segment_size)
488474
{
489475
dsa_area*area;
490476

491477
area=create_internal(place,size,tranche_id,
492-
DSM_HANDLE_INVALID,NULL);
478+
DSM_HANDLE_INVALID,NULL,
479+
init_segment_size,max_segment_size);
493480

494481
/*
495482
* Clean up when the control segment detaches, if a containing DSM segment
@@ -1231,7 +1218,8 @@ static dsa_area *
12311218
create_internal(void*place,size_tsize,
12321219
inttranche_id,
12331220
dsm_handlecontrol_handle,
1234-
dsm_segment*control_segment)
1221+
dsm_segment*control_segment,
1222+
size_tinit_segment_size,size_tmax_segment_size)
12351223
{
12361224
dsa_area_control*control;
12371225
dsa_area*area;
@@ -1241,6 +1229,11 @@ create_internal(void *place, size_t size,
12411229
size_tmetadata_bytes;
12421230
inti;
12431231

1232+
/* Check the initial and maximum block sizes */
1233+
Assert(init_segment_size >=DSA_MIN_SEGMENT_SIZE);
1234+
Assert(max_segment_size >=init_segment_size);
1235+
Assert(max_segment_size <=DSA_MAX_SEGMENT_SIZE);
1236+
12441237
/* Sanity check on the space we have to work in. */
12451238
if (size<dsa_minimum_size())
12461239
elog(ERROR,"dsa_area space must be at least %zu, but %zu provided",
@@ -1270,8 +1263,10 @@ create_internal(void *place, size_t size,
12701263
control->segment_header.prev=DSA_SEGMENT_INDEX_NONE;
12711264
control->segment_header.usable_pages=usable_pages;
12721265
control->segment_header.freed= false;
1273-
control->segment_header.size=DSA_INITIAL_SEGMENT_SIZE;
1266+
control->segment_header.size=size;
12741267
control->handle=control_handle;
1268+
control->init_segment_size=init_segment_size;
1269+
control->max_segment_size=max_segment_size;
12751270
control->max_total_segment_size= (size_t)-1;
12761271
control->total_segment_size=size;
12771272
control->segment_handles[0]=control_handle;
@@ -2127,9 +2122,9 @@ make_new_segment(dsa_area *area, size_t requested_pages)
21272122
* move to huge pages in the future. Then we work back to the number of
21282123
* pages we can fit.
21292124
*/
2130-
total_size=DSA_INITIAL_SEGMENT_SIZE*
2125+
total_size=area->control->init_segment_size*
21312126
((size_t)1 << (new_index /DSA_NUM_SEGMENTS_AT_EACH_SIZE));
2132-
total_size=Min(total_size,DSA_MAX_SEGMENT_SIZE);
2127+
total_size=Min(total_size,area->control->max_segment_size);
21332128
total_size=Min(total_size,
21342129
area->control->max_total_segment_size-
21352130
area->control->total_segment_size);

‎src/include/utils/dsa.h

Lines changed: 42 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -77,6 +77,31 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
7777
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
7878
#defineInvalidDsaPointer ((dsa_pointer) 0)
7979

80+
/*
81+
* The number of bits used to represent the offset part of a dsa_pointer.
82+
* This controls the maximum size of a segment, the maximum possible
83+
* allocation size and also the maximum number of segments per area.
84+
*/
85+
#ifSIZEOF_DSA_POINTER==4
86+
#defineDSA_OFFSET_WIDTH 27/* 32 segments of size up to 128MB */
87+
#else
88+
#defineDSA_OFFSET_WIDTH 40/* 1024 segments of size up to 1TB */
89+
#endif
90+
91+
/*
92+
* The default size of the initial DSM segment that backs a dsa_area created
93+
* by dsa_create. After creating some number of segments of the initial size
94+
* we'll double this size, and so on. Larger segments may be created if
95+
* necessary to satisfy large requests.
96+
*/
97+
#defineDSA_DEFAULT_INIT_SEGMENT_SIZE ((size_t) (1 * 1024 * 1024))
98+
99+
/* The minimum size of a DSM segment. */
100+
#defineDSA_MIN_SEGMENT_SIZE((size_t) (256 * 1024L))
101+
102+
/* The maximum size of a DSM segment. */
103+
#defineDSA_MAX_SEGMENT_SIZE ((size_t) 1 << DSA_OFFSET_WIDTH)
104+
80105
/* Check if a dsa_pointer value is valid. */
81106
#defineDsaPointerIsValid(x) ((x) != InvalidDsaPointer)
82107

@@ -88,6 +113,17 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
88113
#definedsa_allocate0(area,size) \
89114
dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
90115

116+
/* Create dsa_area with default segment sizes */
117+
#definedsa_create(tranch_id) \
118+
dsa_create_ext(tranch_id, DSA_DEFAULT_INIT_SEGMENT_SIZE, \
119+
DSA_MAX_SEGMENT_SIZE)
120+
121+
/* Create dsa_area with default segment sizes in an existing share memory space */
122+
#definedsa_create_in_place(place,size,tranch_id,segment) \
123+
dsa_create_in_place_ext(place, size, tranch_id, segment, \
124+
DSA_DEFAULT_INIT_SEGMENT_SIZE, \
125+
DSA_MAX_SEGMENT_SIZE)
126+
91127
/*
92128
* The type used for dsa_area handles. dsa_handle values can be shared with
93129
* other processes, so that they can attach to them. This provides a way to
@@ -102,10 +138,12 @@ typedef dsm_handle dsa_handle;
102138
/* Sentinel value to use for invalid dsa_handles. */
103139
#defineDSA_HANDLE_INVALID ((dsa_handle) DSM_HANDLE_INVALID)
104140

105-
106-
externdsa_area*dsa_create(inttranche_id);
107-
externdsa_area*dsa_create_in_place(void*place,size_tsize,
108-
inttranche_id,dsm_segment*segment);
141+
externdsa_area*dsa_create_ext(inttranche_id,size_tinit_segment_size,
142+
size_tmax_segment_size);
143+
externdsa_area*dsa_create_in_place_ext(void*place,size_tsize,
144+
inttranche_id,dsm_segment*segment,
145+
size_tinit_segment_size,
146+
size_tmax_segment_size);
109147
externdsa_area*dsa_attach(dsa_handlehandle);
110148
externdsa_area*dsa_attach_in_place(void*place,dsm_segment*segment);
111149
externvoiddsa_release_in_place(void*place);

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