On Thu, Feb 14, 2019 at 08:23:45PM +0800, Ming Lei wrote: > The interrupt affinity spreading mechanism supports to spread out > affinities for one or more interrupt sets. A interrupt set contains one > or more interrupts. Each set is mapped to a specific functionality of a > device, e.g. general I/O queues and read I/O queus of multiqueue block > devices. > > The number of interrupts per set is defined by the driver. It depends on > the total number of available interrupts for the device, which is > determined by the PCI capabilites and the availability of underlying CPU > resources, and the number of queues which the device provides and the > driver wants to instantiate. > > The driver passes initial configuration for the interrupt allocation via > a pointer to struct affinity_desc. > > Right now the allocation mechanism is complex as it requires to have a > loop in the driver to determine the maximum number of interrupts which > are provided by the PCI capabilities and the underlying CPU resources. > This loop would have to be replicated in every driver which wants to > utilize this mechanism. That's unwanted code duplication and error > prone. > > In order to move this into generic facilities it is required to have a > mechanism, which allows the recalculation of the interrupt sets and > their size, in the core code. As the core code does not have any > knowledge about the underlying device, a driver specific callback will > be added to struct affinity_desc, which will be invoked by the core > code. The callback will get the number of available interupts as an > argument, so the driver can calculate the corresponding number and size > of interrupt sets. > > To support this, two modifications for the handling of struct > affinity_desc are required: > > 1) The (optional) interrupt sets size information is contained in a > separate array of integers and struct affinity_desc contains a > pointer to it. > > This is cumbersome and as the maximum number of interrupt sets is > small, there is no reason to have separate storage. Moving the size > array into struct affinity_desc avoids indirections makes the code > simpler. > > 2) At the moment the struct affinity_desc pointer which is handed in from > the driver and passed through to several core functions is marked > 'const'. > > This patch adds callback to recalculate the number and size of interrupt sets, > also removes the 'const' qualifier for 'affd'. > > Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> I know you have something to work out in the affinity.c part of this, but I'm fine with the PCI part, so: Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
