Re: [HACKERS] More stats about skipped vacuums

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: tgl(at)sss(dot)pgh(dot)pa(dot)us
Cc: robertmhaas(at)gmail(dot)com, sawada(dot)mshk(at)gmail(dot)com, michael(dot)paquier(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] More stats about skipped vacuums
Date: 2018-02-09 08:16:35
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At Thu, 08 Feb 2018 18:21:56 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20180208(dot)182156(dot)96551245(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> I suppose that the problem has not been resolved yet..

I found several bugs during studying this but my conclusion here
is that the required decision here is that whether we regard the
unavailability of DSM as a fatal error as we do for out of
memory. Maybe we can go for the direction but just doing it
certainly let some buidfarm animals (at least anole? smew is not
found.) out of their lives.

I've not found the exact cause of the problem that regtest on the
bf animals always suceeded using sysv shmem but "postgres --boot"
by initdb alone can fail using the same mechanism. But regtest
seems to continue working if initdb sets max_connection to 20 or
more. At least it suceeds for me with the values max_connection
= 20 and shared_buffers=50MB on centos.

Finally, I'd like to propose the followings.

- kill dynamic_shared_memory_type = nune just now.

* server stops at startup if DSM is not available.

- Let initdb set max_connection = 20 as the fallback value in
the case. (Another porposed patch) And regression should
succeed with that.

If we are agreed on this, I will be able to go forward.

I want to have opinions on this from the expericed poeple.


Kyotaro Horiguchi
NTT Open Source Software Center

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