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5dc0418fab
Introduce a new GUC recovery_prefetch. When enabled, look ahead in the WAL and try to initiate asynchronous reading of referenced data blocks that are not yet cached in our buffer pool. For now, this is done with posix_fadvise(), which has several caveats. Since not all OSes have that system call, "try" is provided so that it can be enabled where available. Better mechanisms for asynchronous I/O are possible in later work. Set to "try" for now for test coverage. Default setting to be finalized before release. The GUC wal_decode_buffer_size limits the distance we can look ahead in bytes of decoded data. The existing GUC maintenance_io_concurrency is used to limit the number of concurrent I/Os allowed, based on pessimistic heuristics used to infer that I/Os have begun and completed. We'll also not look more than maintenance_io_concurrency * 4 block references ahead. Reviewed-by: Julien Rouhaud <rjuju123@gmail.com> Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com> (earlier version) Reviewed-by: Andres Freund <andres@anarazel.de> (earlier version) Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> (earlier version) Tested-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> (earlier version) Tested-by: Jakub Wartak <Jakub.Wartak@tomtom.com> (earlier version) Tested-by: Dmitry Dolgov <9erthalion6@gmail.com> (earlier version) Tested-by: Sait Talha Nisanci <Sait.Nisanci@microsoft.com> (earlier version) Discussion: https://postgr.es/m/CA%2BhUKGJ4VJN8ttxScUFM8dOKX0BrBiboo5uz1cq%3DAovOddfHpA%40mail.gmail.com |
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| .. | ||
| activity | ||
| adt | ||
| cache | ||
| error | ||
| fmgr | ||
| hash | ||
| init | ||
| mb | ||
| misc | ||
| mmgr | ||
| resowner | ||
| sort | ||
| time | ||
| .gitignore | ||
| errcodes.txt | ||
| Gen_dummy_probes.pl | ||
| Gen_dummy_probes.pl.prolog | ||
| Gen_dummy_probes.sed | ||
| Gen_fmgrtab.pl | ||
| generate-errcodes.pl | ||
| Makefile | ||
| probes.d | ||
| README.Gen_dummy_probes | ||
# Generating dummy probes If Postgres isn't configured with dtrace enabled, we need to generate dummy probes for the entries in probes.d, that do nothing. This is accomplished in Unix via the sed script `Gen_dummy_probes.sed`. We used to use this in MSVC builds using the perl utility `psed`, which mimicked sed. However, that utility disappeared from Windows perl distributions and so we converted the sed script to a perl script to be used in MSVC builds. We still keep the sed script as the authoritative source for generating these dummy probes because except on Windows perl is not a hard requirement when building from a tarball. So, if you need to change the way dummy probes are generated, first change the sed script, and when it's working generate the perl script. This can be accomplished by using the perl utility s2p. s2p is no longer part of the perl core, so it might not be on your system, but it is available on CPAN and also in many package systems. e.g. on Fedora it can be installed using `cpan App::s2p` or `dnf install perl-App-s2p`. The Makefile contains a recipe for regenerating Gen_dummy_probes.pl, so all you need to do is once you have s2p installed is `make Gen_dummy_probes.pl` Note that in a VPATH build this will generate the file in the vpath tree, not the source tree.