From: | Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg_stat_statements issue with parallel maintenance (Was Re: WAL usage calculation patch) |
Date: | 2020-04-08 08:19:19 |
Message-ID: | CA+fd4k6UWRKsaQYwvAnwihp8Bt5RGj8RSZdRgwx7PDoNzb4EnQ@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, 8 Apr 2020 at 16:04, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Apr 8, 2020 at 11:53 AM Masahiko Sawada
> <masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
> >
> > On Wed, 8 Apr 2020 at 14:44, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > >
> > > Thanks for the investigation. I don't see we can do anything special
> > > about this. In an ideal world, this should be done once and not for
> > > each worker but I guess it doesn't matter too much. I am not sure if
> > > it is worth adding a comment for this, what do you think?
> > >
> >
> > I agree with you. If the differences were considerably large probably
> > we would do something but I think we don't need to anything at this
> > time.
> >
>
> Fair enough, can you once check this in back-branches as this needs to
> be backpatched? I will do that once by myself as well.
I've done the same test with HEAD of both REL_12_STABLE and
REL_11_STABLE. I think the patch needs to be backpatched to PG11 where
parallel index creation was introduced. I've attached the patches
for PG12 and PG11 I used for this test for reference.
Here are the results:
* PG12
With no worker:
-[ RECORD 1 ]-------+-------------
shared_blks_hit | 119
shared_blks_read | 44283
total_read_blks | 44402
shared_blks_dirtied | 44262
shared_blks_written | 24925
With 4 workers:
-[ RECORD 1 ]-------+------------
shared_blks_hit | 128
shared_blks_read | 8844
total_read_blks | 8972
shared_blks_dirtied | 8822
shared_blks_written | 5393
With 4 workers after patching:
-[ RECORD 1 ]-------+------------
shared_blks_hit | 140
shared_blks_read | 44284
total_read_blks | 44424
shared_blks_dirtied | 44262
shared_blks_written | 26574
* PG11
With no worker:
-[ RECORD 1 ]-------+------------
shared_blks_hit | 124
shared_blks_read | 44284
total_read_blks | 44408
shared_blks_dirtied | 44263
shared_blks_written | 24908
With 4 workers:
-[ RECORD 1 ]-------+-------------
shared_blks_hit | 132
shared_blks_read | 8910
total_read_blks | 9042
shared_blks_dirtied | 8888
shared_blks_written | 5370
With 4 workers after patched:
-[ RECORD 1 ]-------+-------------
shared_blks_hit | 144
shared_blks_read | 44285
total_read_blks | 44429
shared_blks_dirtied | 44263
shared_blks_written | 26861
Regards,
--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Attachment | Content-Type | Size |
---|---|---|
bufferusage_create_index_pg12.patch | application/x-patch | 4.4 KB |
bufferusage_create_index_pg11.patch | application/x-patch | 4.4 KB |
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