From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steven Winfield <Steven.Winfield@cantabcapital.com>
Cc: pgsql-performance@lists.postgresql.org <pgsql-performance@lists.postgresql.org>
Subject: Re: GCC 8.3.0 vs. 9.0.1
Date: Tue, 07 May 2019 13:05:59 -0400
Message-ID: <4470.1557248759@sss.pgh.pa.us> (raw)
In-Reply-To: <E9FA92C2921F31408041863B74EE4C2001BD66841B@CCPMAILDAG03.cantab.local>
References: <E9FA92C2921F31408041863B74EE4C2001BD66841B@CCPMAILDAG03.cantab.local>
Steven Winfield <Steven.Winfield@cantabcapital.com> writes:
> A few days ago a blog post appeared on phoronix.com[1] comparing GCC 8.3.0 against 9.0.1 on Intel cascadelake processors.
> A notable difference was seen in the PostgreSQL benchmark (v10.3, pgbench, read/write, more detail below), both when compiling with -march=native and -march=skylake:
> I'm interested to know the devs' take on this is - does GCC 9 contain some new feature(s) that are particularly well suited to compiling and optimising Postgres? Or was GCC 8 particularly bad?
Given the described test setup, I'd put basically no stock in these
numbers. It's unlikely that this test case's performance is CPU-bound
per se; more likely, I/O and lock contention are dominant factors.
So I'm afraid whatever they're measuring is a more-or-less chance
effect rather than a real system-wide code improvement.
It is an interesting report, all the same.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, Steven.Winfield@cantabcapital.com, pgsql-performance@lists.postgresql.org
Subject: Re: GCC 8.3.0 vs. 9.0.1
In-Reply-To: <4470.1557248759@sss.pgh.pa.us>
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