On Thu, Oct 11, 2018 at 11:50 AM Nadav Har'El <[email protected]> wrote:

>
> On Thu, Oct 11, 2018 at 10:45 AM Qixuan Wu <[email protected]> wrote:
>
>> Hi All,
>>
>> I saw the paper,  it said schedule latency is less than linux thread,
>> about 328ns.
>>
>> Guest OS
>>
>> Colocated
>>
>> Apart
>>
>> Linux
>>
>> 905 ns
>>
>> 13148 ns
>>
>> OSv
>>
>> 328 ns
>>
>> 1402 ns
>>
>> Anyone can tell where is the test case code ?
>>
>
> tests/misc-ctxsw.cc
>
> To run it in OSv you can do "scripts/build image=tests" and then
> "scripts/run.py -e tests/misc-ctxsw.so"
>
> What this test does is to create two threads (on the same core, or on two
> different cores) which alternate waking the other thread and then waiting
> (via a condition variable).
> Strangely I just tested this again on my laptop (which is newer than the
> paper), and got (for the colocated case) in OSv is around 400ns, and in
> Linux around 1800ns, so the difference is even more pronounced today.
>

Perhaps you are seeing the effects of Meltdown mitigation in Linux context
switching paths?

- Pekka

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