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Add pg_backend_memory_contexts system view. 

This view displays the usages of all the memory contexts of the server
process attached to the current session. This information is useful to
investigate the cause of backend-local memory bloat.

This information can be also collected by calling
MemoryContextStats(TopMemoryContext) via a debugger. But this technique
cannot be uesd in some environments because no debugger is available there.
And it outputs lots of text messages and it's not easy to analyze them.
So, pg_backend_memory_contexts view allows us to access to backend-local
memory contexts information more easily.

Bump catalog version.

Author: Atsushi Torikoshi, Fujii Masao
Reviewed-by: Tatsuhito Kasahara, Andres Freund, Daniel Gustafsson, Robert Haas, Michael Paquier
Discussion: https://postgr.es/m/72a656e0f71d0860161e0b3f67e4d771@oss.nttdata.com
This commit is contained in:
Fujii Masao 2020-08-19 15:34:43 +09:00
parent 07f32fcd23
commit 3e98c0bafb
6 changed files with 283 additions and 1 deletions
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122
doc/src/sgml/catalogs.sgml
View File

@ -9226,6 +9226,11 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
<entry>available versions of extensions</entry>
</row>
<row>
<entry><link linkend="view-pg-backend-memory-contexts"><structname>pg_backend_memory_contexts</structname></link></entry>
<entry>backend memory contexts</entry>
</row>
<row>
<entry><link linkend="view-pg-config"><structname>pg_config</structname></link></entry>
<entry>compile-time configuration parameters</entry>
@ -9577,6 +9582,123 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
</para>
</sect1>
<sect1 id="view-pg-backend-memory-contexts">
<title><structname>pg_backend_memory_contexts</structname></title>
<indexterm zone="view-pg-backend-memory-contexts">
<primary>pg_backend_memory_contexts</primary>
</indexterm>
<para>
The view <structname>pg_backend_memory_contexts</structname> displays all
the memory contexts of the server process attached to the current session.
</para>
<para>
<structname>pg_backend_memory_contexts</structname> contains one row
for each memory context.
</para>
<table>
<title><structname>pg_backend_memory_contexts</structname> Columns</title>
<tgroup cols="1">
<thead>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
Column Type
</para>
<para>
Description
</para></entry>
</row>
</thead>
<tbody>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>name</structfield> <type>text</type>
</para>
<para>
Name of the memory context
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>ident</structfield> <type>text</type>
</para>
<para>
Identification information of the memory context. This field is truncated at 1024 bytes
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>parent</structfield> <type>text</type>
</para>
<para>
Name of the parent of this memory context
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>level</structfield> <type>int4</type>
</para>
<para>
Distance from TopMemoryContext in context tree
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_bytes</structfield> <type>int8</type>
</para>
<para>
Total bytes allocated for this memory context
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_nblocks</structfield> <type>int8</type>
</para>
<para>
Total number of blocks allocated for this memory context
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>free_bytes</structfield> <type>int8</type>
</para>
<para>
Free space in bytes
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>free_chunks</structfield> <type>int8</type>
</para>
<para>
Total number of free chunks
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>used_bytes</structfield> <type>int8</type>
</para>
<para>
Used space in bytes
</para></entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
<sect1 id="view-pg-config">
<title><structname>pg_config</structname></title>

3
src/backend/catalog/system_views.sql
View File

@ -554,6 +554,9 @@ CREATE VIEW pg_shmem_allocations AS
REVOKE ALL ON pg_shmem_allocations FROM PUBLIC;
REVOKE EXECUTE ON FUNCTION pg_get_shmem_allocations() FROM PUBLIC;
CREATE VIEW pg_backend_memory_contexts AS
SELECT * FROM pg_get_backend_memory_contexts();
-- Statistics views
CREATE VIEW pg_stat_all_tables AS

138
src/backend/utils/mmgr/mcxt.c
View File

@ -21,8 +21,10 @@
#include "postgres.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
@ -67,6 +69,12 @@ static void MemoryContextStatsPrint(MemoryContext context, void *passthru,
#define AssertNotInCriticalSection(context) \
Assert(CritSectionCount == 0 || (context)->allowInCritSection)
/* ----------
* The max bytes for showing identifiers of MemoryContext.
* ----------
*/
#define MEMORY_CONTEXT_IDENT_DISPLAY_SIZE 1024
/*****************************************************************************
* EXPORTED ROUTINES *
*****************************************************************************/
@ -1220,3 +1228,133 @@ pchomp(const char *in)
n--;
return pnstrdup(in, n);
}
/*
* PutMemoryContextsStatsTupleStore
* One recursion level for pg_get_backend_memory_contexts.
*/
static void
PutMemoryContextsStatsTupleStore(Tuplestorestate *tupstore,
TupleDesc tupdesc, MemoryContext context,
const char *parent, int level)
{
#define PG_GET_BACKEND_MEMORY_CONTEXTS_COLS 9
Datum values[PG_GET_BACKEND_MEMORY_CONTEXTS_COLS];
bool nulls[PG_GET_BACKEND_MEMORY_CONTEXTS_COLS];
MemoryContextCounters stat;
MemoryContext child;
const char *name;
const char *ident;
AssertArg(MemoryContextIsValid(context));
name = context->name;
ident = context->ident;
/*
* To be consistent with logging output, we label dynahash contexts
* with just the hash table name as with MemoryContextStatsPrint().
*/
if (ident && strcmp(name, "dynahash") == 0)
{
name = ident;
ident = NULL;
}
/* Examine the context itself */
memset(&stat, 0, sizeof(stat));
(*context->methods->stats) (context, NULL, (void *) &level, &stat);
memset(values, 0, sizeof(values));
memset(nulls, 0, sizeof(nulls));
if (name)
values[0] = CStringGetTextDatum(name);
else
nulls[0] = true;
if (ident)
{
int idlen = strlen(ident);
char clipped_ident[MEMORY_CONTEXT_IDENT_DISPLAY_SIZE];
/*
* Some identifiers such as SQL query string can be very long,
* truncate oversize identifiers.
*/
if (idlen >= MEMORY_CONTEXT_IDENT_DISPLAY_SIZE)
idlen = pg_mbcliplen(ident, idlen, MEMORY_CONTEXT_IDENT_DISPLAY_SIZE - 1);
memcpy(clipped_ident, ident, idlen);
clipped_ident[idlen] = '\0';
values[1] = CStringGetTextDatum(clipped_ident);
}
else
nulls[1] = true;
if (parent)
values[2] = CStringGetTextDatum(parent);
else
nulls[2] = true;
values[3] = Int32GetDatum(level);
values[4] = Int64GetDatum(stat.totalspace);
values[5] = Int64GetDatum(stat.nblocks);
values[6] = Int64GetDatum(stat.freespace);
values[7] = Int64GetDatum(stat.freechunks);
values[8] = Int64GetDatum(stat.totalspace - stat.freespace);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
for (child = context->firstchild; child != NULL; child = child->nextchild)
{
PutMemoryContextsStatsTupleStore(tupstore, tupdesc,
child, name, level + 1);
}
}
/*
* pg_get_backend_memory_contexts
* SQL SRF showing backend memory context.
*/
Datum
pg_get_backend_memory_contexts(PG_FUNCTION_ARGS)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
MemoryContext per_query_ctx;
MemoryContext oldcontext;
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("materialize mode required, but it is not allowed in this context")));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
oldcontext = MemoryContextSwitchTo(per_query_ctx);
tupstore = tuplestore_begin_heap(true, false, work_mem);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
MemoryContextSwitchTo(oldcontext);
PutMemoryContextsStatsTupleStore(tupstore, tupdesc,
TopMemoryContext, NULL, 0);
/* clean up and return the tuplestore */
tuplestore_donestoring(tupstore);
return (Datum) 0;
}

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202007251
#define CATALOG_VERSION_NO 202008191
#endif

9
src/include/catalog/pg_proc.dat
View File

@ -7807,6 +7807,15 @@
proargnames => '{name,off,size,allocated_size}',
prosrc => 'pg_get_shmem_allocations' },
# memory context of local backend
{ oid => '2282', descr => 'information about all memory contexts of local backend',
proname => 'pg_get_backend_memory_contexts', prorows => '100', proretset => 't',
provolatile => 'v', proparallel => 'r', prorettype => 'record', proargtypes => '',
proallargtypes => '{text,text,text,int4,int8,int8,int8,int8,int8}',
proargmodes => '{o,o,o,o,o,o,o,o,o}',
proargnames => '{name, ident, parent, level, total_bytes, total_nblocks, free_bytes, free_chunks, used_bytes}',
prosrc => 'pg_get_backend_memory_contexts' },
# non-persistent series generator
{ oid => '1066', descr => 'non-persistent series generator',
proname => 'generate_series', prorows => '1000',

10
src/test/regress/expected/rules.out
View File

@ -1324,6 +1324,16 @@ pg_available_extensions| SELECT e.name,
e.comment
FROM (pg_available_extensions() e(name, default_version, comment)
LEFT JOIN pg_extension x ON ((e.name = x.extname)));
pg_backend_memory_contexts| SELECT pg_get_backend_memory_contexts.name,
pg_get_backend_memory_contexts.ident,
pg_get_backend_memory_contexts.parent,
pg_get_backend_memory_contexts.level,
pg_get_backend_memory_contexts.total_bytes,
pg_get_backend_memory_contexts.total_nblocks,
pg_get_backend_memory_contexts.free_bytes,
pg_get_backend_memory_contexts.free_chunks,
pg_get_backend_memory_contexts.used_bytes
FROM pg_get_backend_memory_contexts() pg_get_backend_memory_contexts(name, ident, parent, level, total_bytes, total_nblocks, free_bytes, free_chunks, used_bytes);
pg_config| SELECT pg_config.name,
pg_config.setting
FROM pg_config() pg_config(name, setting);