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Allow specifying initial and maximum segment sizes for DSA.

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Previously, the DSA segment size always started with 1MB and grew up
to DSA_MAX_SEGMENT_SIZE. It was inconvenient in certain scenarios,
such as when the caller desired a soft constraint on the total DSA
segment size, limiting it to less than 1MB.

This commit introduces the capability to specify the initial and
maximum DSA segment sizes when creating a DSA area, providing more
flexibility and control over memory usage.

Reviewed-by: John Naylor, Tomas Vondra
Discussion: https://postgr.es/m/CAD21AoAYGGC1ePjVX0H%2Bpp9rH%3D9vuPK19nNOiu12NprdV5TVJA%40mail.gmail.com
pull/159/head
Masahiko Sawada 2 years ago
parent 1f42337be5
commit bb952c8c8b
2 changed files with 71 additions and 38 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 63
      src/backend/utils/mmgr/dsa.c
  2. 46
      src/include/utils/dsa.h

63
src/backend/utils/mmgr/dsa.c
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@ -59,14 +59,6 @@
#include "utils/memutils.h"
#include "utils/resowner.h"
/*
* The size of the initial DSM segment that backs a dsa_area created by
* dsa_create. After creating some number of segments of this size we'll
* double this size, and so on. Larger segments may be created if necessary
* to satisfy large requests.
*/
#define DSA_INITIAL_SEGMENT_SIZE ((size_t) (1 * 1024 * 1024))
/*
* How many segments to create before we double the segment size. If this is
* low, then there is likely to be a lot of wasted space in the largest
@ -76,17 +68,6 @@
*/
#define DSA_NUM_SEGMENTS_AT_EACH_SIZE 2
/*
* The number of bits used to represent the offset part of a dsa_pointer.
* This controls the maximum size of a segment, the maximum possible
* allocation size and also the maximum number of segments per area.
*/
#if SIZEOF_DSA_POINTER == 4
#define DSA_OFFSET_WIDTH 27 /* 32 segments of size up to 128MB */
#else
#define DSA_OFFSET_WIDTH 40 /* 1024 segments of size up to 1TB */
#endif
/*
* The maximum number of DSM segments that an area can own, determined by
* the number of bits remaining (but capped at 1024).
@ -97,9 +78,6 @@
/* The bitmask for extracting the offset from a dsa_pointer. */
#define DSA_OFFSET_BITMASK (((dsa_pointer) 1 << DSA_OFFSET_WIDTH) - 1)
/* The maximum size of a DSM segment. */
#define DSA_MAX_SEGMENT_SIZE ((size_t) 1 << DSA_OFFSET_WIDTH)
/* Number of pages (see FPM_PAGE_SIZE) per regular superblock. */
#define DSA_PAGES_PER_SUPERBLOCK 16
@ -318,6 +296,10 @@ typedef struct
dsa_segment_index segment_bins[DSA_NUM_SEGMENT_BINS];
/* The object pools for each size class. */
dsa_area_pool pools[DSA_NUM_SIZE_CLASSES];
/* initial allocation segment size */
size_t init_segment_size;
/* maximum allocation segment size */
size_t max_segment_size;
/* The total size of all active segments. */
size_t total_segment_size;
/* 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)
static dsa_area *create_internal(void *place, size_t size,
int tranche_id,
dsm_handle control_handle,
dsm_segment *control_segment);
dsm_segment *control_segment,
size_t init_segment_size,
size_t max_segment_size);
static dsa_area *attach_internal(void *place, dsm_segment *segment,
dsa_handle handle);
static void check_for_freed_segments(dsa_area *area);
@ -434,7 +418,7 @@ static void rebin_segment(dsa_area *area, dsa_segment_map *segment_map);
* we require the caller to provide one.
*/
dsa_area *
dsa_create(int tranche_id)
dsa_create_ext(int tranche_id, size_t init_segment_size, size_t max_segment_size)
{
dsm_segment *segment;
dsa_area *area;
@ -443,7 +427,7 @@ dsa_create(int tranche_id)
* Create the DSM segment that will hold the shared control object and the
* first segment of usable space.
*/
segment = dsm_create(DSA_INITIAL_SEGMENT_SIZE, 0);
segment = dsm_create(init_segment_size, 0);
/*
* All segments backing this area are pinned, so that DSA can explicitly
@ -455,9 +439,10 @@ dsa_create(int tranche_id)
/* Create a new DSA area with the control object in this segment. */
area = create_internal(dsm_segment_address(segment),
DSA_INITIAL_SEGMENT_SIZE,
init_segment_size,
tranche_id,
dsm_segment_handle(segment), segment);
dsm_segment_handle(segment), segment,
init_segment_size, max_segment_size);
/* Clean up when the control segment detaches. */
on_dsm_detach(segment, &dsa_on_dsm_detach_release_in_place,
@ -483,13 +468,15 @@ dsa_create(int tranche_id)
* See dsa_create() for a note about the tranche arguments.
*/
dsa_area *
dsa_create_in_place(void *place, size_t size,
int tranche_id, dsm_segment *segment)
dsa_create_in_place_ext(void *place, size_t size,
int tranche_id, dsm_segment *segment,
size_t init_segment_size, size_t max_segment_size)
{
dsa_area *area;
area = create_internal(place, size, tranche_id,
DSM_HANDLE_INVALID, NULL);
DSM_HANDLE_INVALID, NULL,
init_segment_size, max_segment_size);
/*
* Clean up when the control segment detaches, if a containing DSM segment
@ -1231,7 +1218,8 @@ static dsa_area *
create_internal(void *place, size_t size,
int tranche_id,
dsm_handle control_handle,
dsm_segment *control_segment)
dsm_segment *control_segment,
size_t init_segment_size, size_t max_segment_size)
{
dsa_area_control *control;
dsa_area *area;
@ -1241,6 +1229,11 @@ create_internal(void *place, size_t size,
size_t metadata_bytes;
int i;
/* Check the initial and maximum block sizes */
Assert(init_segment_size >= DSA_MIN_SEGMENT_SIZE);
Assert(max_segment_size >= init_segment_size);
Assert(max_segment_size <= DSA_MAX_SEGMENT_SIZE);
/* Sanity check on the space we have to work in. */
if (size < dsa_minimum_size())
elog(ERROR, "dsa_area space must be at least %zu, but %zu provided",
@ -1270,8 +1263,10 @@ create_internal(void *place, size_t size,
control->segment_header.prev = DSA_SEGMENT_INDEX_NONE;
control->segment_header.usable_pages = usable_pages;
control->segment_header.freed = false;
control->segment_header.size = DSA_INITIAL_SEGMENT_SIZE;
control->segment_header.size = size;
control->handle = control_handle;
control->init_segment_size = init_segment_size;
control->max_segment_size = max_segment_size;
control->max_total_segment_size = (size_t) -1;
control->total_segment_size = size;
control->segment_handles[0] = control_handle;
@ -2127,9 +2122,9 @@ make_new_segment(dsa_area *area, size_t requested_pages)
* move to huge pages in the future. Then we work back to the number of
* pages we can fit.
*/
total_size = DSA_INITIAL_SEGMENT_SIZE *
total_size = area->control->init_segment_size *
((size_t) 1 << (new_index / DSA_NUM_SEGMENTS_AT_EACH_SIZE));
total_size = Min(total_size, DSA_MAX_SEGMENT_SIZE);
total_size = Min(total_size, area->control->max_segment_size);
total_size = Min(total_size,
area->control->max_total_segment_size -
area->control->total_segment_size);

46
src/include/utils/dsa.h
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@ -77,6 +77,31 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
#define InvalidDsaPointer ((dsa_pointer) 0)
/*
* The number of bits used to represent the offset part of a dsa_pointer.
* This controls the maximum size of a segment, the maximum possible
* allocation size and also the maximum number of segments per area.
*/
#if SIZEOF_DSA_POINTER == 4
#define DSA_OFFSET_WIDTH 27 /* 32 segments of size up to 128MB */
#else
#define DSA_OFFSET_WIDTH 40 /* 1024 segments of size up to 1TB */
#endif
/*
* The default size of the initial DSM segment that backs a dsa_area created
* by dsa_create. After creating some number of segments of the initial size
* we'll double this size, and so on. Larger segments may be created if
* necessary to satisfy large requests.
*/
#define DSA_DEFAULT_INIT_SEGMENT_SIZE ((size_t) (1 * 1024 * 1024))
/* The minimum size of a DSM segment. */
#define DSA_MIN_SEGMENT_SIZE ((size_t) (256 * 1024L))
/* The maximum size of a DSM segment. */
#define DSA_MAX_SEGMENT_SIZE ((size_t) 1 << DSA_OFFSET_WIDTH)
/* Check if a dsa_pointer value is valid. */
#define DsaPointerIsValid(x) ((x) != InvalidDsaPointer)
@ -88,6 +113,17 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
#define dsa_allocate0(area, size) \
dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
/* Create dsa_area with default segment sizes */
#define dsa_create(tranch_id) \
dsa_create_ext(tranch_id, DSA_DEFAULT_INIT_SEGMENT_SIZE, \
DSA_MAX_SEGMENT_SIZE)
/* Create dsa_area with default segment sizes in an existing share memory space */
#define dsa_create_in_place(place, size, tranch_id, segment) \
dsa_create_in_place_ext(place, size, tranch_id, segment, \
DSA_DEFAULT_INIT_SEGMENT_SIZE, \
DSA_MAX_SEGMENT_SIZE)
/*
* The type used for dsa_area handles. dsa_handle values can be shared with
* other processes, so that they can attach to them. This provides a way to
@ -102,10 +138,12 @@ typedef dsm_handle dsa_handle;
/* Sentinel value to use for invalid dsa_handles. */
#define DSA_HANDLE_INVALID ((dsa_handle) DSM_HANDLE_INVALID)
extern dsa_area *dsa_create(int tranche_id);
extern dsa_area *dsa_create_in_place(void *place, size_t size,
int tranche_id, dsm_segment *segment);
extern dsa_area *dsa_create_ext(int tranche_id, size_t init_segment_size,
size_t max_segment_size);
extern dsa_area *dsa_create_in_place_ext(void *place, size_t size,
int tranche_id, dsm_segment *segment,
size_t init_segment_size,
size_t max_segment_size);
extern dsa_area *dsa_attach(dsa_handle handle);
extern dsa_area *dsa_attach_in_place(void *place, dsm_segment *segment);
extern void dsa_release_in_place(void *place);

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