Re: [PATCH for-next] RDMA/hns: Create QP/CQ with selected QPN/CQN for bank load balance

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Nov 10, 2020 at 09:19:39AM +0000, liweihang wrote:
> On 2020/11/6 21:37, Jason Gunthorpe wrote:
> > On Fri, Nov 06, 2020 at 01:52:57AM +0000, liweihang wrote:
> > 
> >> There are 8 banks and each of them has a counter which represents
> >> how many QPs are using this bank. We first find the bank with the
> >> smallest count, and then try to find a QPN belongs to this bank
> >> according to the bitmap.  The ida will find an unused ID starting
> >> from 0, I think it can't meet our needs. If we use ida here, the
> >> code may looks like:
> > 
> > I don't understand, why wouldn't the ida give you a free QPN in a bank
> > directly?
> > 
> > Jason
> > 
> 
> Hi Jason,
> 
> Here is the QPN that belongs to each bank:
> 
> QPN on bank0：0, 8, 16, 24 ... <lower three bits is 0>
> QPN on bank1: 1, 9, 17, 25 ... <lower three bits is 1>
> QPN on bank2: 2, 10, 18, 26 ... <lower three bits is 2>
> ...
> QPN on bank6: 6, 14, 22, 30 ... <lower three bits is 6>
> QPN on bank7: 7, 15, 23, 31 ... <lower three bits is 7>
> 
> If bank 6 is the one with the lowest load, then we need to find a
> valid QPN belongs to bank6, that means, the lower 3 bits of QPN is
> 6 and it hasn't been used.
> We can't find out a way to use ida in this situation because the
> QPNs of each bank are discontinuous.

Each bank has an IDA, you allocate from the IDA then shift left and or
in the bank number

Jason