doing also VM cache snapshot and restore with pg_prewarm, having more information of the VM inside PostgreSQL - Mailing list pgsql-hackers

From Cedric Villemain
Subject doing also VM cache snapshot and restore with pg_prewarm, having more information of the VM inside PostgreSQL
Date
Msg-id aa94afb9-0bfe-4421-b8b4-8a6e67ce55b1@abcSQL.com
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List pgsql-hackers

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
PostgreSQL Expertise, Support, Training, R&D

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