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From: Shawn Debnath <sdn@amazon.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Refactoring the checkpointer's fsync request queue
Date: Tue, 5 Mar 2019 08:07:15 -0800
Message-ID: <20190305160715.GA26468@f01898859afd.ant.amazon.com> (raw)
In-Reply-To: <CA+hUKGLiUQ2mMQBTencjZKt88io5m7eguRmuxbaPqPTyL6ERtg@mail.gmail.com>
References: <20190222224853.ahvm3bf52zqr7k7h@alap3.anarazel.de>
	<CA+hUKG+i5+0Grt9O9gtv1YHASP6R3rfb8074or0j=fFoY6YvTw@mail.gmail.com>
	<20190222230916.5mfsqn3oesd2nxiz@alap3.anarazel.de>
	<20190222234549.GA7397@f01898859afd.ant.amazon.com>
	<20190222235742.4oed46wocpjfpoa5@alap3.anarazel.de>
	<20190227212653.GA7171@f01898859afd.ant.amazon.com>
	<CA+hUKG+2EuoDhVBdieOKnneFX14SeuRp7z0WG2PSOMJt8ks3qw@mail.gmail.com>
	<CA+hUKGKF7QvUi2ST4R5vd_PVdcztBTXB23ZJwoj_ASoujrbsmQ@mail.gmail.com>
	<2a1667c64cc0485bb781704876ac5a0a@EX13D05UWC002.ant.amazon.com>
	<CA+hUKGLiUQ2mMQBTencjZKt88io5m7eguRmuxbaPqPTyL6ERtg@mail.gmail.com>

On Tue, Mar 05, 2019 at 10:45:37PM +1300, Thomas Munro wrote:
> On Tue, Mar 5, 2019 at 2:25 PM Shawn Debnath <sdn@amazon.com> wrote:
> > [v11 patch]
> 
> Thanks.  Hmm, something is wrong here because make check is
> dramatically slower -- for example the "insert" test runs in ~8-13
> seconds instead of the usual ~0.2 seconds according to Travis,
> AppVeyor and my local FreeBSD system (note that fsync is disabled so
> it's not that -- it must be bogus queue-related CPU?)

Confirmed. Patch shows 8900 ms vs 192 ms on master for the insert test.  
Interesting! It's reproducible so should be able to figure out what's 
going on. The only thing we do in ForwardSyncRequest() is split up the 8 
bits into 2x4 bits and copy the FileTagData structure to the 
checkpointer queue. Will report back what I find.

-- 
Shawn Debnath
Amazon Web Services (AWS)




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  Cc: sdn@amazon.com, thomas.munro@gmail.com, andres@anarazel.de, 9erthalion6@gmail.com, robertmhaas@gmail.com
  Subject: Re: Refactoring the checkpointer's fsync request queue
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