Messages in this thread | | | Date | Wed, 11 Jun 2008 12:21:47 -0700 | From | Max Krasnyansky <> | Subject | Re: workqueue cpu affinity |
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Oleg Nesterov wrote: > On 06/10, Max Krasnyansky wrote: >> Here is some backgound on this. Full cpu isolation requires some tweaks to the >> workqueue handling. Either the workqueue threads need to be moved (which is my >> current approach), or work needs to be redirected when it's submitted. > > _IF_ we have to do this, I think it is much better to move cwq->thread. Ok. btw That's what I'm doing now from user-space.
>> Peter Zijlstra wrote: >>> The advantage of creating a more flexible or fine-grained flush is that >>> large machine also profit from it. >> I agree, our current workqueue flush scheme is expensive because it has to >> schedule on each online cpu. So yes improving flush makes sense in general. > > Yes, it is easy to implement flush_work(struct work_struct *work) which > only waits for that work, so it can't hang unless it was enqueued on the > isolated cpu. > > But in most cases it is enough to just do > > if (cancel_work_sync(work)) > work->func(work); Cool. That would work. btw Somehow I thought that you already implemented flush_work(). I do not see it 2.6.25 but I could've sworn that I saw a patch flying by. Must have been something else. Do you mind adding that ?
> Or we can add flush_workqueue_cpus(struct workqueue_struct *wq, cpumask_t *cpu_map). That'd be special casing. I mean something will have to know what cpus cannot be flushed. I liked your proposal above much better.
> But I don't think we should change the behaviour of flush_workqueue(). > >> This will require a bit of surgery across the entire tree. There is a lot of >> code that calls flush_scheduled_work() > > Almost all of them should be changed to use cancel_work_sync().
That'd be a lot of changes.
git grep flush_scheduled_work | wc 154 376 8674
Hmm, I guess maybe not that bad. I might actually do that :-).
Max
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