Re: POC: Cache data in GetSnapshotData()

On Wed, Mar 16, 2016 at 1:33 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-03-16 13:29:22 -0400, Robert Haas wrote:
>> Whoa. At 64 clients, we're hardly getting any benefit, but then by 88
>> clients, we're getting a huge benefit. I wonder why there's that sharp
>> change there.
>
> What's the specifics of the machine tested? I wonder if it either
> correlates with the number of hardware threads, real cores, or cache
> sizes.

I think this was done on cthulhu, whose /proc/cpuinfo output ends this way:

processor : 127
vendor_id : GenuineIntel
cpu family : 6
model : 47
model name : Intel(R) Xeon(R) CPU E7- 8830 @ 2.13GHz
stepping : 2
microcode : 0x37
cpu MHz : 2129.000
cache size : 24576 KB
physical id : 3
siblings : 16
core id : 25
cpu cores : 8
apicid : 243
initial apicid : 243
fpu : yes
fpu_exception : yes
cpuid level : 11
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts
rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64
monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1
sse4_2 x2apic popcnt aes lahf_lm ida arat epb dtherm tpr_shadow vnmi
flexpriority ept vpid
bogomips : 4266.62
clflush size : 64
cache_alignment : 64
address sizes : 44 bits physical, 48 bits virtual
power management:

--
Robert Haas
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