On Thu, 12 Feb 2015, Jesper Dangaard Brouer wrote: > > > This is quite an expensive lock with irqsave. > > > > Yes but we take it for all partial pages. > > Sure, that is good, but this might be a contention point. In a micro > benchmark, this contention should be visible, but in real use-cases the > given subsystem also need to spend time to use these elements before > requesting a new batch (as long as NIC cleanup cycles don't get too > synchronized)
Yes definitely it will be a contention point. There is no way around it. > > Yup the page access is shared but there is one per page. Contention is > > unlikely. > > Yes, contention is unlikely, but every atomic operation is expensive. > On my system the measured cost is 8ns, and a lock/unlock does two, thus > 16ns. Which we then do per page freelist. Not sure what we can do about this. > > We can require that interrupt are off when the functions are called. Then > > we can avoid the "save" part? > > Yes, we could also do so with an "_irqoff" variant of the func call, > but given we are defining the API we can just require this from the > start. Allright. Lets do that then. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
