Re: 60 core performance with 9.3

On 11/07/14 20:22, Andres Freund wrote:
> On 2014-07-11 12:40:15 +1200, Mark Kirkwood wrote:

>> Postgres 9.4 beta
>> rwlock patch
>> pgbench scale = 2000
>>
> On that scale - that's bigger than shared_buffers IIRC - I'd not expect
> the patch to make much of a difference.
>

Right - we did test with it bigger (can't recall exactly how big), but
will retry again after setting the numa parameters below.

>> #
>>       8.82%        postgres  [kernel.kallsyms]        [k]
>> _raw_spin_lock_irqsave
>>                    |
>>                    --- _raw_spin_lock_irqsave
>>                       |
>>                       |--75.69%-- pagevec_lru_move_fn
>>                       |          __lru_cache_add
>>                       |          lru_cache_add
>>                       |          putback_lru_page
>>                       |          migrate_pages
>>                       |          migrate_misplaced_page
>>                       |          do_numa_page
>>                       |          handle_mm_fault
>>                       |          __do_page_fault
>>                       |          do_page_fault
>>                       |          page_fault
>
> So, the majority of the time is spent in numa page migration. Can you
> disable numa_balancing? I'm not sure if your kernel version does that at
> runtime or whether you need to reboot.
> The kernel.numa_balancing sysctl might work. Otherwise you probably need
> to boot with numa_balancing=0.
>
> It'd also be worthwhile to test this with numactl --interleave.
>

That was my feeling too - but I had no idea what the magic switch was to
tame it (appears to be in 3.13 kernels), will experiment and report
back. Thanks again!

Mark