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Commit98f320e

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Increase default vacuum_buffer_usage_limit to 2MB.
The BAS_VACUUM ring size has been 256kB since commitd526575 introducedthe mechanism 17 years ago. Commit1cbbee0 recently made itconfigurable but retained the traditional default. The correct defaultsize has been debated for years, but 256kB is certainly very small.VACUUM soon needs to write back data it dirtied only 32 blocks ago,which usually requires flushing the WAL. New experiments in prefetchingpages for VACUUM exacerbated the problem by crashing into dirty dataeven sooner. Let's make the default 2MB. That's 1.6% of the defaulttoy buffer pool size, and 0.2% of 1GB, which would be a considered asmall shared_buffers setting for a real system these days. Users arestill free to set the GUC to a different value.Reviewed-by: Andres Freund <andres@anarazel.de>Discussion:https://postgr.es/m/20240403221257.md4gfki3z75cdyf6%40awork3.anarazel.deDiscussion:https://postgr.es/m/CA%2BhUKGLY4Q4ZY4f1rvnFtv6%2BPkjNf8MejdPkcju3Qii9DYqqcQ%40mail.gmail.com
1 parent3bd8439 commit98f320e

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5 files changed

+5
-5
lines changed

5 files changed

+5
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lines changed

‎doc/src/sgml/config.sgml

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@@ -1961,7 +1961,7 @@ include_dir 'conf.d'
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valid sizes range from <literal>128 kB</literal> to
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<literal>16 GB</literal>. If the specified size would exceed 1/8 the
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size of <varname>shared_buffers</varname>, the size is silently capped
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to that value. The default value is <literal>256 kB</literal>. If
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to that value. The default value is <literal>2MB</literal>. If
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this value is specified without units, it is taken as kilobytes. This
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parameter can be set at any time. It can be overridden for
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<xref linkend="sql-vacuum"/> and <xref linkend="sql-analyze"/>

‎src/backend/storage/buffer/freelist.c

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Original file line numberDiff line numberDiff line change
@@ -561,7 +561,7 @@ GetAccessStrategy(BufferAccessStrategyType btype)
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ring_size_kb=16*1024;
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break;
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caseBAS_VACUUM:
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ring_size_kb=256;
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ring_size_kb=2048;
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break;
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default:

‎src/backend/utils/init/globals.c

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@@ -143,7 +143,7 @@ intmax_parallel_workers = 8;
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intMaxBackends=0;
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/* GUC parameters for vacuum */
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intVacuumBufferUsageLimit=256;
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intVacuumBufferUsageLimit=2048;
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intVacuumCostPageHit=1;
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intVacuumCostPageMiss=2;

‎src/backend/utils/misc/guc_tables.c

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@@ -2275,7 +2275,7 @@ struct config_int ConfigureNamesInt[] =
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GUC_UNIT_KB
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},
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&VacuumBufferUsageLimit,
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256,0,MAX_BAS_VAC_RING_SIZE_KB,
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2048,0,MAX_BAS_VAC_RING_SIZE_KB,
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check_vacuum_buffer_usage_limit,NULL,NULL
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},
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‎src/backend/utils/misc/postgresql.conf.sample

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@@ -166,7 +166,7 @@
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# mmap
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# (change requires restart)
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#min_dynamic_shared_memory = 0MB# (change requires restart)
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#vacuum_buffer_usage_limit =256kB# size of vacuum and analyze buffer access strategy ring;
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#vacuum_buffer_usage_limit =2MB# size of vacuum and analyze buffer access strategy ring;
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# 0 to disable vacuum buffer access strategy;
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# range 128kB to 16GB
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