On Thu, Sep 20, 2018 at 08:10:36AM +0300, Leon Romanovsky wrote: > On Wed, Sep 19, 2018 at 03:27:19PM -0600, Jason Gunthorpe wrote: > > On Tue, Sep 18, 2018 at 10:56:55AM +0300, Leon Romanovsky wrote: > > > From: Leon Romanovsky <leonro@xxxxxxxxxxxx> > > > > > > There is no need to do custom logic to allocate indexes while kernel > > > provides specific API for that. > > > > I think if we are going to do this then the RDMA_MAX_PORTS should be > > increased to match the memory overhead of the IDA, at least. > > > > Otherwise we are paying a greater allocation cost and getting nothing > > for it. > > > > IIRC an IDA allocates bitmaps in 64*64 bits chunks, so RDMA_MAX_PORTS > > should be >> 4096 ? > > > > Maybe it should be 1<<MINORBITS like NVME does? > > > > Reserving more minor numbers is basically free other than the tracking > > bitmap, which is why Huy was so stingy when this was introduced.. > > I don't see the need to do extra optimization in memory footprint for > rare and not significant case, but do see the great value of using > standard kernel APIs with proper coding pattern in opposite to to home > grown implementation of the same thing. find_bit is the usual API to use here if the bitmap is small, IDA is the right API when the bitmap gets larger. If you want to use IDA you should increase the bitmap range to be appropriate for IDA.. Jason
