Re: [RFC PATCH] kick ksoftirqd more often to please soft lockup detector

[Dan Williams]

On Wed, Feb 29, 2012 at 1:17 AM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
> On Tue, 2012-02-28 at 14:16 -0800, Dan Williams wrote:
>> Looks like everyone is guilty:
>>
>> [  422.765336] softirq took longer than 1/4 tick: 3 NET_RX ffffffff813f0aa0
>> ...
>> [  423.971878] softirq took longer than 1/4 tick: 4 BLOCK ffffffff812519c8
>> [  423.985093] softirq took longer than 1/4 tick: 6 TASKLET ffffffff8103422e
>> [  423.993157] softirq took longer than 1/4 tick: 7 SCHED ffffffff8105e2e1
>> [  424.001018] softirq took longer than 1/4 tick: 9 RCU ffffffff810a0fed
>> [  424.008691] softirq loop took longer than 1/2 tick need_resched:
>
> /me kicks himself for not printing the actual duration.. :-)
>
>> As expected whenever that 1/2 tick message gets emitted the softirq
>> handler is almost running in a need_resched() context.
>
> Yeah.. that's quite expected.
>
>> So is it a good idea to get more aggressive about scheduling ksoftrrqd?
>
> Nah, moving away from softirq more like. I'll put moving the
> load-balancer into a kthread on the todo list. And it looks like
> everybody else should move to kthreads too.

I seem to recall this running into resistance (but maybe things have
changed in the last few years)?

https://lkml.org/lkml/2007/6/29/155
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/