Re: FreeBSD 7.0-RELEASE: Can I specify the maximum number of cores that kernel can recognize ?

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Re: FreeBSD 7.0-RELEASE: Can I specify the maximum number of cores that kernel can recognize ?

Kris Kennaway-3
Hattori, Shigehiro wrote:

> Hi,
>
> I try to measure Bind caching name server's multi threading performance on
> FreeBSD 7 , like below.
>
> --
> # of cores    query/second
> 1                 xx
> 2                 xx
> 4                 xx
> 6                 xx
> 8                 xx
> --
>
> My testing machine has 8 cores. ( quad core * 2 )
>
> I'd like to specify the maximum # of cores that kernel can recognize.
> Can I specify the maximum # of cores with boot parameters or something ?

You can disable the cores you do not want by turning off their lapic.
Add to /boot/loader.conf:

hint.lapic.0.disabled=1 turns off lapic 0, etc.  Cross-reference against
dmesg:

FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
  cpu0 (BSP): APIC ID:  0 <---- disables this core
  cpu1 (AP): APIC ID:  1
  cpu2 (AP): APIC ID:  2
  cpu3 (AP): APIC ID:  3
  cpu4 (AP): APIC ID:  4
  cpu5 (AP): APIC ID:  5
  cpu6 (AP): APIC ID:  6
  cpu7 (AP): APIC ID:  7

> I've already done Bind multi threading performance test on Linux (
> CentOS5 )
> In case of CentOS5 , I specified maximum # of cores with grub.conf 
> "maxcpus=1
> or 2 or 4 or ..."
>
> # cat /etc/grub.conf
> title CentOS (2.6.18-53.1.21.el5PAE)
>        root (hd0,1)
>        kernel /boot/vmlinuz-2.6.18-53.1.21.el5PAE ro root=LABEL=/ rhgb
> quiet maxcpus=6
>        initrd /boot/initrd-2.6.18-53.1.21.el5PAE.img
> #
>
> The following is the results I did on CentOS5 ( kernel:
> 2.6.18-53.1.21.el5 ).
>
> -- Bind 9.4.2 caching name server on CentOS5
> # of cores    query/second    CPU ( named )
> 1                 3578                99.9
> 2                 5070                196
> 4                 6608                362
> 6                 9042                527
> 8                 10552               678
> --
>
> - Bind's machine spec
>
> CPU: Intel Xeon E5346  2.3GH ( quad core * 2 )
> Memory: 4GB
> Bind 9.4.2
> Cache size: 1400MB
> Max recursive clients: 50000
>
> - Traffic generetor: queryperf
> Query list: all queries are uniq ( that means "No answer in the cache" )

Make sure you are resolving these queries against another local server.
  If you're querying random servers in the internet then you're mostly
going to be benchmarking your uplink latency and the maximum query rate
will be limited by the number of broken servers you query that do not
respond but time out.

Those numbers are quite low even for Linux; on similar hardware I can
achieve 60000 qps on Linux and about 105000 qps on FreeBSD:

http://people.freebsd.org/~kris/scaling/bind-pt.png

With 1gb ethernet I have to query from multiple clients to get that high
because of request latency (with 10gbe I can saturate from a single
client).  I was not disabling cores but limiting the number of bind
threads, which should be approximately the same thing especially for 8
threads.

Kris

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