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From: MichaelDBA <MichaelDBA@sqlexec.com>
To: Scott Ribe <scott_ribe@elevated-dev.com>
Cc: jian xu <jamesxu@outlook.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Re: checkpoint process use too much memory
Date: Mon, 20 Apr 2020 15:37:48 -0400
Message-ID: <fcb5bde4-437d-913e-cb1f-3fdb866a805a@sqlexec.com> (raw)
In-Reply-To: <B2103F5D-29DD-465C-A43B-9973EC313799@elevated-dev.com>
References: <MN2PR05MB68322593E34D4BF78AD45137A1D70@MN2PR05MB6832.namprd05.prod.outlook.com>
	<5193b00d175f2e06a171ba375f1ef723e1700de4.camel@cybertec.at>
	<MN2PR05MB6832AA29B8D72FCA59D29E19A1D40@MN2PR05MB6832.namprd05.prod.outlook.com>
	<C7D8AF88-5A80-4F1E-B3AF-7BB01369FD87@elevated-dev.com>
	<MN2PR05MB6832881823D2B12D767C8C67A1D40@MN2PR05MB6832.namprd05.prod.outlook.com>
	<B2103F5D-29DD-465C-A43B-9973EC313799@elevated-dev.com>

You said: "the work_mem is 128MB, so they could use mostly 25GB memory,"

But work_mem is sometimes very deceiving based on types of queries 
executed.  You may need many work_mem buffers for a single query. So 8 
buffers used = 1GB.  So it could conceivable surpass 25GB easily.  I 
would do some explaining on your SQL workload.

Regards,
Michael Vitale



Scott Ribe wrote on 4/20/2020 3:23 PM:
>> On Apr 20, 2020, at 1:13 PM, jian xu <jamesxu@outlook.com> wrote:
>>
>> Do you mean the file cache will be counted in postgres checkpointer memory usage?
> No, it won't be counted as PG memory. I just mean that free memory low is not a sign of a problem, when it's file cache.
>
>

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