doing also VM cache snapshot and restore with pg_prewarm, having more information of the VM inside PostgreSQL

Hi,

for 15 years pgfincore has been sitting quietly and being used in large
setups to help in HA and resources management.
It can perfectly stay as is, to be honest I was expecting to one day
include a windows support and propose that to PostgreSQL, it appears
getting support on linux and BSD is more than enough today.

So I wonder if there are interest for having virtual memory snapshot and
restore operations with, for example, pg_prewarm/autowarm ?

Some usecases covered: snapshot/restore cache around cronjobs, around
dumps, switchover, failover, on stop/start of postgres (think kernel
upgrade with a cold restart), ...

pgfincore also provides some nice information with mincore (on FreeBSD
mincore is more interesting) or cachestat, again it can remain as an out
of tree extension but I will be happy to add to commitfest if there are
interest from the community.
An example of cachestat output:

postgres=# select *from vm_relation_cachestat('foo',range:=1024*32);
block_start | block_count | nr_pages | nr_cache | nr_dirty |
nr_writeback | nr_evicted | nr_recently_evicted
-------------+-------------+----------+----------+----------+--------------+------------+---------------------

          0 |       32768 |    65536 |    62294 |        0 |
           0 |       3242 |                3242
      32768 |       32768 |    65536 |    39279 |        0 |
           0 |      26257 |               26257
      65536 |       32768 |    65536 |    22516 |        0 |
           0 |      43020 |               43020
      98304 |       32768 |    65536 |    24944 |        0 |
           0 |      40592 |               40592
     131072 |        1672 |     3344 |      487 |        0 |
           0 |       2857 |                2857

Comments?

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Cédric Villemain +33 (0)6 20 30 22 52
https://Data-Bene.io
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