On 08/20/2014 06:14 PM, Mark Kirkwood wrote:
Notwithstanding the above results, my workmate Matt made an interesting observation: the scaling graph for (our) 60 core box (HT off), looks just like the one for our 32 core box with HT *on*.
Hmm. I know this sounds stupid and unlikely, but has anyone actually tested PostgreSQL on a system with more than 64 legitimate cores? The work Robert Haas did to fix the CPU locking way back when showed significant improvements up to 64, but so far as I know, nobody really tested beyond that.
I seem to remember similar choking effects when pre-9.2 systems encountered high CPU counts. I somehow doubt Intel would allow their HT architecture to regress so badly from Nehalem, which is almost 3-generations old at this point. This smells like something in the software stack, up to and including the Linux kernel.
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