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Enable IO concurrency on all systems

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Previously effective_io_concurrency and maintenance_io_concurrency could not
be set above 0 on machines without fadvise support. AIO enables IO concurrency
without such support, via io_method=worker.

Currently only subsystems using the read stream API will take advantage of
this. Other users of maintenance_io_concurrency (like recovery prefetching)
which leverage OS advice directly will not benefit from this change. In those
cases, maintenance_io_concurrency will have no effect on I/O behavior.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/CAAKRu_atGgZePo=_g6T3cNtfMf0QxpvoUh5OUqa_cnPdhLd=gw@mail.gmail.com
This commit is contained in:
Andres Freund 2025-03-30 19:14:55 -04:00
parent ae3df4b341
commit 2a5e709e72
10 changed files with 14 additions and 67 deletions
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16
doc/src/sgml/config.sgml
View File

@ -2585,8 +2585,7 @@ include_dir 'conf.d'
session attempts to initiate in parallel. The allowed range is
<literal>1</literal> to <literal>1000</literal>, or
<literal>0</literal> to disable issuance of asynchronous I/O requests.
The default is <literal>16</literal> on supported systems, otherwise
<literal>0</literal>.
The default is <literal>16</literal>.
</para>
<para>
@ -2597,8 +2596,9 @@ include_dir 'conf.d'
</para>
<para>
On systems without prefetch advice support, attempting to configure
any value other than <literal>0</literal> will error out.
On systems with prefetch advice support,
<varname>effective_io_concurrency</varname> also controls the
prefetch distance.
</para>
<para>
@ -2621,10 +2621,10 @@ include_dir 'conf.d'
for maintenance work that is done on behalf of many client sessions.
</para>
<para>
The default is <literal>16</literal> on supported systems, otherwise
<literal>0</literal>. This value can be overridden for tables in a
particular tablespace by setting the tablespace parameter of the same
name (see <xref linkend="sql-altertablespace"/>).
The default is <literal>16</literal>. This value can be overridden
for tables in a particular tablespace by setting the tablespace
parameter of the same name (see <xref
linkend="sql-altertablespace"/>).
</para>
</listitem>
</varlistentry>

2
doc/src/sgml/ref/alter_tablespace.sgml
View File

@ -88,7 +88,7 @@ ALTER TABLESPACE <replaceable>name</replaceable> RESET ( <replaceable class="par
and <varname>maintenance_io_concurrency</varname>.
Setting these values for a particular tablespace will override the
planner's usual estimate of the cost of reading pages from tables in
that tablespace, and the executor's prefetching behavior, as established
that tablespace, and how many concurrent I/Os are issued, as established
by the configuration parameters of the
same name (see <xref linkend="guc-seq-page-cost"/>,
<xref linkend="guc-random-page-cost"/>,

2
doc/src/sgml/ref/create_tablespace.sgml
View File

@ -110,7 +110,7 @@ CREATE TABLESPACE <replaceable class="parameter">tablespace_name</replaceable>
and <varname>maintenance_io_concurrency</varname>.
Setting these values for a particular tablespace will override the
planner's usual estimate of the cost of reading pages from tables in
that tablespace, and the executor's prefetching behavior, as established
that tablespace, and how many concurrent I/Os are issued, as established
by the configuration parameters of the
same name (see <xref linkend="guc-seq-page-cost"/>,
<xref linkend="guc-random-page-cost"/>,

8
src/backend/access/common/reloptions.c
View File

@ -361,11 +361,7 @@ static relopt_int intRelOpts[] =
RELOPT_KIND_TABLESPACE,
ShareUpdateExclusiveLock
},
#ifdef USE_PREFETCH
-1, 0, MAX_IO_CONCURRENCY
#else
0, 0, 0
#endif
},
{
{
@ -374,11 +370,7 @@ static relopt_int intRelOpts[] =
RELOPT_KIND_TABLESPACE,
ShareUpdateExclusiveLock
},
#ifdef USE_PREFETCH
-1, 0, MAX_IO_CONCURRENCY
#else
0, 0, 0
#endif
},
{
{

30
src/backend/commands/variable.c
View File

@ -1145,7 +1145,6 @@ check_cluster_name(char **newval, void **extra, GucSource source)
void
assign_maintenance_io_concurrency(int newval, void *extra)
{
#ifdef USE_PREFETCH
/*
* Reconfigure recovery prefetching, because a setting it depends on
* changed.
@ -1153,7 +1152,6 @@ assign_maintenance_io_concurrency(int newval, void *extra)
maintenance_io_concurrency = newval;
if (AmStartupProcess())
XLogPrefetchReconfigure();
#endif
}
/*
@ -1249,34 +1247,6 @@ check_default_with_oids(bool *newval, void **extra, GucSource source)
return true;
}
bool
check_effective_io_concurrency(int *newval, void **extra, GucSource source)
{
#ifndef USE_PREFETCH
if (*newval != 0)
{
GUC_check_errdetail("\"%s\" must be set to 0 on platforms that lack support for issuing read-ahead advice.",
"effective_io_concurrency");
return false;
}
#endif /* USE_PREFETCH */
return true;
}
bool
check_maintenance_io_concurrency(int *newval, void **extra, GucSource source)
{
#ifndef USE_PREFETCH
if (*newval != 0)
{
GUC_check_errdetail("\"%s\" must be set to 0 on platforms that lack support for issuing read-ahead advice.",
"maintenance_io_concurrency");
return false;
}
#endif /* USE_PREFETCH */
return true;
}
bool
check_ssl(bool *newval, void **extra, GucSource source)
{

4
src/backend/utils/misc/guc_tables.c
View File

@ -3235,7 +3235,7 @@ struct config_int ConfigureNamesInt[] =
&effective_io_concurrency,
DEFAULT_EFFECTIVE_IO_CONCURRENCY,
0, MAX_IO_CONCURRENCY,
check_effective_io_concurrency, NULL, NULL
NULL, NULL, NULL
},
{
@ -3249,7 +3249,7 @@ struct config_int ConfigureNamesInt[] =
&maintenance_io_concurrency,
DEFAULT_MAINTENANCE_IO_CONCURRENCY,
0, MAX_IO_CONCURRENCY,
check_maintenance_io_concurrency, assign_maintenance_io_concurrency,
NULL, assign_maintenance_io_concurrency,
NULL
},

4
src/backend/utils/misc/postgresql.conf.sample
View File

@ -198,8 +198,8 @@
# - I/O -
#backend_flush_after = 0 # measured in pages, 0 disables
#effective_io_concurrency = 16 # 1-1000; 0 disables prefetching
#maintenance_io_concurrency = 16 # 1-1000; 0 disables prefetching
#effective_io_concurrency = 16 # 1-1000; 0 disables issuing multiple simultaneous IO requests
#maintenance_io_concurrency = 16 # 1-1000; same as effective_io_concurrency
#io_max_combine_limit = 128kB # usually 1-128 blocks (depends on OS)
# (change requires restart)
#io_combine_limit = 128kB # usually 1-128 blocks (depends on OS)

5
src/bin/initdb/initdb.c
View File

@ -1402,11 +1402,6 @@ setup_config(void)
repltok, true);
#endif
#ifndef USE_PREFETCH
conflines = replace_guc_value(conflines, "effective_io_concurrency",
"0", true);
#endif
#ifdef WIN32
conflines = replace_guc_value(conflines, "update_process_title",
"off", true);

6
src/include/storage/bufmgr.h
View File

@ -158,14 +158,8 @@ extern PGDLLIMPORT int bgwriter_lru_maxpages;
extern PGDLLIMPORT double bgwriter_lru_multiplier;
extern PGDLLIMPORT bool track_io_timing;
/* only applicable when prefetching is available */
#ifdef USE_PREFETCH
#define DEFAULT_EFFECTIVE_IO_CONCURRENCY 16
#define DEFAULT_MAINTENANCE_IO_CONCURRENCY 16
#else
#define DEFAULT_EFFECTIVE_IO_CONCURRENCY 0
#define DEFAULT_MAINTENANCE_IO_CONCURRENCY 0
#endif
extern PGDLLIMPORT int effective_io_concurrency;
extern PGDLLIMPORT int maintenance_io_concurrency;

4
src/include/utils/guc_hooks.h
View File

@ -61,8 +61,6 @@ extern bool check_default_text_search_config(char **newval, void **extra, GucSou
extern void assign_default_text_search_config(const char *newval, void *extra);
extern bool check_default_with_oids(bool *newval, void **extra,
GucSource source);
extern bool check_effective_io_concurrency(int *newval, void **extra,
GucSource source);
extern bool check_huge_page_size(int *newval, void **extra, GucSource source);
extern void assign_io_method(int newval, void *extra);
extern bool check_io_max_concurrency(int *newval, void **extra, GucSource source);
@ -83,8 +81,6 @@ extern bool check_log_stats(bool *newval, void **extra, GucSource source);
extern bool check_log_timezone(char **newval, void **extra, GucSource source);
extern void assign_log_timezone(const char *newval, void *extra);
extern const char *show_log_timezone(void);
extern bool check_maintenance_io_concurrency(int *newval, void **extra,
GucSource source);
extern void assign_maintenance_io_concurrency(int newval, void *extra);
extern void assign_io_max_combine_limit(int newval, void *extra);
extern void assign_io_combine_limit(int newval, void *extra);