From: Fujii Masao <masao.fujii@oss.nttdata.com>
To: torikoshia <torikoshia@oss.nttdata.com>
To: Michael Paquier <michael@paquier.xyz>
To: Kasahara Tatsuhito <kasahara.tatsuhito@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Robert Haas <robertmhaas@gmail.com>
Subject: Re: Creating a function for exposing memory usage of backend process
Date: Mon, 24 Aug 2020 13:13:39 +0900
Message-ID: <07da4267-74bf-4a6b-3312-4ab7c1e72f66@oss.nttdata.com> (raw)
In-Reply-To: <c9515ae497b4a077360a31547782acb8@oss.nttdata.com>
References: <261eebda3e1909475162b968e5a4ad2b@oss.nttdata.com>
<66ae5b88-208d-96fa-c20a-fb539b597859@oss.nttdata.com>
<20200819135545.GC19121@paquier.xyz>
<1414992.1597849297@sss.pgh.pa.us>
<20200819225343.c7rxteydi35nhrdp@alap3.anarazel.de>
<1554676.1597886946@sss.pgh.pa.us>
<20200820014301.5pr7qjugnvpovu62@alap3.anarazel.de>
<d97ad430-444d-9ec8-21dd-a1584569309b@oss.nttdata.com>
<CAP0=ZVJ5VZsUYLFkc-E5_JHTc1ZdemX28VgQqUXJLTywC=9hfA@mail.gmail.com>
<a8f3c385e9edeba4833c712270d6e6d9@oss.nttdata.com>
<20200822121641.GE2108@paquier.xyz>
<c9515ae497b4a077360a31547782acb8@oss.nttdata.com>
On 2020/08/24 13:01, torikoshia wrote:
> On 2020-08-22 21:18, Michael Paquier wrote:
>
> Thanks for reviewing!
>
>> On Fri, Aug 21, 2020 at 11:27:06PM +0900, torikoshia wrote:
>>> OK. Added a regression test on sysviews.sql.
>>> (0001-Added-a-regression-test-for-pg_backend_memory_contex.patch)
>>>
>>> Fujii-san gave us an example, but I added more simple one considering
>>> the simplicity of other tests on that.
>>
>> What you have sent in 0001 looks fine to me. A small test is much
>> better than nothing.
+1
But as I proposed upthread, what about a bit complicated test as follows,
e.g., to confirm that the internal logic for level works expectedly?
SELECT name, ident, parent, level, total_bytes >= free_bytes FROM pg_backend_memory_contexts WHERE level = 0;
>>
>>> Added a patch for relocating the codes to mcxtfuncs.c.
>>> (patches/0001-Rellocated-the-codes-for-pg_backend_memory_contexts-.patch)
Thanks for the patch! Looks good to me.
Barring any objection, I will commit this patch at first.
>>
>> The same code is moved around line-by-line.
>>
>>> Of course, this restriction makes pg_backend_memory_contexts hard to use
>>> when the user of the target session is not granted pg_monitor because the
>>> scope of this view is session local.
>>>
>>> In this case, I imagine additional operations something like temporarily
>>> granting pg_monitor to that user.
>>
>> Hmm. I am not completely sure either that pg_monitor is the best fit
>> here, because this view provides information about a bunch of internal
>> structures. Something that could easily be done though is to revoke
>> the access from public, and then users could just set up GRANT
>> permissions post-initdb, with pg_monitor as one possible choice. This
>> is the safest path by default, and this stuff is of a caliber similar
>> to pg_shmem_allocations in terms of internal contents.
>
> I think this is a better way than what I did in
> 0001-Rellocated-the-codes-for-pg_backend_memory_contexts-.patch.
You mean 0001-Restrict-the-access-to-pg_backend_memory_contexts-to.patch?
> Attached a patch.
Thanks for updating the patch! This also looks good to me.
>> It seems to me that you are missing one "REVOKE ALL on
>> pg_backend_memory_contexts FROM PUBLIC" in patch 0003.
>>
>> By the way, if that was just for me, I would remove used_bytes, which
>> is just a computation from the total and free numbers. I'll defer
>> that point to Fujii-san.
Yeah, I was just thinking that displaying also used_bytes was useful,
but this might be inconsistent with the other views' ways.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
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Cc: masao.fujii@oss.nttdata.com, torikoshia@oss.nttdata.com, michael@paquier.xyz, kasahara.tatsuhito@gmail.com, andres@anarazel.de, tgl@sss.pgh.pa.us, robertmhaas@gmail.com
Subject: Re: Creating a function for exposing memory usage of backend process
In-Reply-To: <07da4267-74bf-4a6b-3312-4ab7c1e72f66@oss.nttdata.com>
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