Re: GCC 8.3.0 vs. 9.0.1 - Mailing list pgsql-performance

From Peter Geoghegan
Subject Re: GCC 8.3.0 vs. 9.0.1
Date
Msg-id CAH2-WzmvCYeQUVgaoeQBxKpBoGU8v4vbNPObFeydBjNcW2SQNA@mail.gmail.com
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In response to Re: GCC 8.3.0 vs. 9.0.1  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: GCC 8.3.0 vs. 9.0.1
List pgsql-performance
On Tue, May 7, 2019 at 10:06 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 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.

Or a compiler bug. Link-time optimizations give the compiler a view of
the program as a whole, not just a single TU at a time. This enables
it to perform additional aggressive optimization.

-- 
Peter Geoghegan



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