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 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 max_connections t

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 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'

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

2014-02-05 Thread Tom Lane
Andres Freund 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, but I think it do

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 wrote: > >> > A quick hack (attached) making BufferDescriptor 64byte aligned indeed > >> > restored performance across all max_connections settings. It's not > >> > surprising that a misaligned buf

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 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 f

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 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: http://www.postgresql.org/mailpref/pgsql-

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

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 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 90, from 91... >