Avi Kivity wrote: > On 10/26/2009 05:38 PM, Gregory Haskins wrote: >>>> Instead of a lockless attribute, how about a ->set_atomic() method. >>>> For >>>> msi this can be the same as ->set(), for non-msi it can be a function >>>> that schedules the work (which will eventually call ->set()). >>>> >>>> The benefit is that we make a decision only once, when preparing the >>>> routing entry, and install that decision in the routing entry >>>> instead of >>>> making it again and again later. >>>> >>> Yeah, I like this idea. I think we can also get rid of the custom >>> workqueue if we do this as well, TBD. >>> >> So I looked into this. It isn't straight forward because you need to >> retain some kind of state across the deferment on a per-request basis >> (not per-GSI). Today, this state is neatly tracked into the irqfd >> object itself (e.g. it knows to toggle the GSI). >> > > Yes, and it also contains the work_struct. > > What if we make the work_struct (and any additional state) part of the > set_atomic() argument list? Does it simplify things? Hmmm, that might not, but we could do a kmalloc(GFP_ATOMIC) for such parameters. Considering this is just a safety net, perhaps this would work fine. > >> So while generalizing this perhaps makes sense at some point, especially >> if irqfd-like interfaces get added, it probably doesn't make a ton of >> sense to expend energy on it ATM. It is basically a generalization of >> the irqfd deferrment code. Lets just wait until we have a user beyond >> irqfd for now. Sound acceptable? >> > > I'll look at v3, but would really like to disentangle this. Ok, I will see what I can do. I need at least a v4 to get rid of the dependency on the now defunct v3:1/3 patch per yesterdays discussion. Kind Regards, -Greg
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