syscall cost freebsd vs linux ?

[Luigi Rizzo]

a quick and easy way is to run the syscall in a tight loop for a sufficient
long time (1s or more) and use "time" to measure it.

At 100ns per call you need about 10M cycles to do one second.

cheers
luigi



On Mon, Nov 26, 2012 at 3:39 AM, Lukasz Wojcik <lukasz.wojcik at zoho.com>wrote:

> On 11/19/12 20:32, Luigi Rizzo wrote:
>
>> today i was comparing the performance of some netmap-related code
>> on FreeBSD and Linux (RELENG_9 vs 3.2) and i was surprised to see that
>> our system calls are significantly slower.
>> On comparable hardware (i7-2600k vs E5-1650) the syscall
>> getppid() takes about 95ns on FreeBSD and 38ns on linux.
>>
>> (i make sure not to use gettimeofday(), which in linux is through vdso,
>> and getpid(), which is cached by glibc).
>>
>> Any idea on why there is this difference and whether/how
>> we can reduce it ?
>>
>>
> I'm curious about how did you measure that ? Could you write some more
> about your methodology ?
>
> -LW
>
>  cheers
>> luigi
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>
>
>


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