From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Christoph Berg <myon@debian.org>
Cc: Andres Freund <andres@anarazel.de>
Cc: Jason Petersen <jason@citusdata.com>
Cc: pgsql-pkg-debian@postgresql.org, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] [PATCH] relocation truncated to fit: citus build failure on s390x
Date: Tue, 30 May 2017 10:12:46 -0400
Message-ID: <11629.1496153566@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+TgmoYk0eSy=wfiusUHsZvN+NF+R4RaoJic0y=Rz3ErKhwzyA@mail.gmail.com>
References: <A37C3A5E-DDEA-40C9-BB67-133B42E4E0A8@citusdata.com>
<980D4281-A01F-4F5D-9874-FFED701F403F@citusdata.com>
<20160426151339.GF12563@msg.df7cb.de>
<20160426153235.GA2862@msg.df7cb.de>
<20160427230516.44fuzdxlifch2wwp@alap3.anarazel.de>
<20160428080824.GA22412@msg.df7cb.de>
<20170529155850.qojdfrwkkqnjb3ap@msg.df7cb.de>
<27883.1496087111@sss.pgh.pa.us>
<CA+TgmoYk0eSy=wfiusUHsZvN+NF+R4RaoJic0y=Rz3ErKhwzyA@mail.gmail.com>
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Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, May 29, 2017 at 3:45 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I wonder what the overhead is of using -fPIC when -fpic would be
>> sufficient.
> Do we have an idea how to measure the increased overhead? Just from
> reading the description, I'm guessing that the increased cost would
> happen when the extension calls back into core, but maybe that doesn't
> happen often enough to worry about?
My gut feeling is that it'd be a pretty distributed cost, because every
internal cross-reference in the .so (for instance, loading the address of
a string literal) would involve a bit more overhead to support a wider
offset field. An easy thing to look at would be how much the code expands
by. That might or might not be a good proxy for the runtime slowdown
percentage, but it seems like it ought to serve as a zero-order
approximation.
regards, tom lane
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To: pgsql-pkg-debian@postgresql.org
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, myon@debian.org, andres@anarazel.de, jason@citusdata.com, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] [PATCH] relocation truncated to fit: citus build failure on s390x
In-Reply-To: <11629.1496153566@sss.pgh.pa.us>
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