On 2015/5/22 4:39, Tejun Heo wrote:
> Hello, Li.
>
> On Wed, May 20, 2015 at 06:05:37PM +0800, Zefan Li wrote:
>>> The latency is bound by synchronize_sched_expedited(). Given the way
>>> cgroups are used in majority of setups (process migration happening
>>> only during service / session setups), I think this should be okay.
>>
>> Actually process migration can happen quite frequently, for example in
>> Android phones, and that's why Google had an out-of-tree patch to remove
>> the synchronize_rcu() in that path, which turned out to be buggy.
>
> It's still not a very frequent operation tho. We're talking about
> users switching fore/background jobs here and the expedited
> synchronization w/ preemption enabled doesn't take much time. In
> addition, as it currently stands, android is doing memory charge
> immigration on each fore/background switches. I'm pretty doubtful
> this would make any difference.
>
I did some testing with my laptop.
Moving a task between 2 cgroups for 10W times with one or two threads:
1T 2T
orig 3.36s 3.65s
orig+tj 3.55s 6.31s
orig+sync_rcu 16.69s 28.47s (only 1000 times)
The overhead looks acceptable.
--
To unsubscribe from this list: send the line "unsubscribe cgroups" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
