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Commit813fde7

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Standardize "read-ahead advice" terminology.
Commit6654bb9 added macOS's equivalent of POSIX_FADV_WILLNEED, andchanged some explicit references to posix_fadvise to use this moregeneral name for the concept. Update some remaining references.Reviewed-by: Peter Eisentraut <peter@eisentraut.org>Discussion:https://postgr.es/m/0827edec-1317-4917-a186-035eb1e3241d%40eisentraut.org
1 parent1c61fd8 commit813fde7

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‎src/backend/access/transam/xlogprefetcher.c‎

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@@ -1083,7 +1083,7 @@ check_recovery_prefetch(int *new_value, void **extra, GucSource source)
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#ifndefUSE_PREFETCH
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if (*new_value==RECOVERY_PREFETCH_ON)
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{
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GUC_check_errdetail("\"recovery_prefetch\" is not supported on platforms that lackposix_fadvise().");
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GUC_check_errdetail("\"recovery_prefetch\" is not supported on platforms that lacksupport for issuing read-ahead advice.");
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return false;
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}
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#endif

‎src/backend/storage/aio/read_stream.c‎

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@@ -24,16 +24,17 @@
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* already. There is no benefit to looking ahead more than one block, so
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* distance is 1. This is the default initial assumption.
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*
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* B) I/O is necessary, but fadvise is undesirable because the access is
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* sequential, or impossible because direct I/O is enabled or the system
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* doesn't support fadvise. There is no benefit in looking ahead more than
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* B) I/O is necessary, but read-ahead advice is undesirable because the
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* access is sequential and we can rely on the kernel's read-ahead heuristics,
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* or impossible because direct I/O is enabled, or the system doesn't support
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* read-ahead advice. There is no benefit in looking ahead more than
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* io_combine_limit, because in this case the only goal is larger read system
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* calls. Looking further ahead would pin many buffers and perform
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* speculative worklooking aheadfor no benefit.
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* speculative work for no benefit.
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*
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* C) I/O is necessary, it appears random, and this system supports fadvise.
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* We'll look further ahead in order to reach the configured level of I/O
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* concurrency.
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* C) I/O is necessary, it appearsto berandom, and this system supports
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*read-ahead advice.We'll look further ahead in order to reach the
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*configured level of I/Oconcurrency.
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*
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* The distance increases rapidly and decays slowly, so that it moves towards
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* those levels as different I/O patterns are discovered. For example, a

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