Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-05 Thread Andres Freund
On 2014-02-04 16:24:02 -0800, Peter Geoghegan wrote: On Mon, Feb 3, 2014 at 3:38 PM, Andres Freund and...@2ndquadrant.com wrote: A quick hack (attached) making BufferDescriptor 64byte aligned indeed restored performance across all max_connections settings. It's not surprising that a

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-05 Thread Tom Lane
Andres Freund and...@2ndquadrant.com writes: On 2014-02-04 16:24:02 -0800, Peter Geoghegan wrote: I suspect that the scenario described in this article accounts for the quite noticeable effect reported: http://danluu.com/3c-conflict I don't think that's applicable here. Maybe, or maybe not,

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-05 Thread Andres Freund
On 2014-02-05 09:57:11 -0500, Tom Lane wrote: Andres Freund and...@2ndquadrant.com writes: On 2014-02-04 16:24:02 -0800, Peter Geoghegan wrote: I suspect that the scenario described in this article accounts for the quite noticeable effect reported: http://danluu.com/3c-conflict I don't

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-05 Thread Peter Geoghegan
On Tue, Feb 4, 2014 at 4:24 PM, Peter Geoghegan p...@heroku.com wrote: There is something you have not drawn explicit attention to that is very interesting. If we take REL9_3_STABLE tip to be representative (built with full -O2 optimization, no assertions just debugging symbols), setting

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-04 Thread Andres Freund
On 2014-02-04 00:38:19 +0100, Andres Freund wrote: A quick hack (attached) making BufferDescriptor 64byte aligned indeed restored performance across all max_connections settings. It's not surprising that a misaligned buffer descriptor causes problems - there'll be plenty of false

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-04 Thread Peter Geoghegan
On Tue, Feb 4, 2014 at 4:21 AM, Andres Freund and...@2ndquadrant.com wrote: Which imo means fixing this got more important... I strongly agree. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription:

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-04 Thread Peter Geoghegan
On Mon, Feb 3, 2014 at 3:38 PM, Andres Freund and...@2ndquadrant.com wrote: A quick hack (attached) making BufferDescriptor 64byte aligned indeed restored performance across all max_connections settings. It's not surprising that a misaligned buffer descriptor causes problems - there'll be

Re: [HACKERS] Re: Misaligned BufferDescriptors causing major performance problems on AMD

2014-02-03 Thread Andres Freund
On 2014-02-03 15:17:13 -0800, Peter Geoghegan wrote: On Sun, Feb 2, 2014 at 7:13 AM, Andres Freund and...@2ndquadrant.com wrote: Just as reference, we're talking about a performance degradation from 475963.613865 tps to 197744.913556 in a pgbench -S -cj64 just by setting max_connections to