On 07/13/2017 10:30 AM, weiping zhang wrote: > On Thu, Jul 13, 2017 at 10:14:31AM -0600, Jens Axboe wrote: >> On 07/13/2017 10:10 AM, weiping zhang wrote: >>> one hw queue only has one hctx, reduce it's number same as nr_hw_queues. >> >> What happens if a device registers with eg 4 hw queues, then later >> calls blk_mq_update_nr_hw_queues()? >> > > your means, 10 cpu, and device has 10 hw queues, but only register 4, > and then update it to 10, no place store new hctx. Am i understanding > right ? if yes, could you tell me why driver do that ? thanks. It doesn't matter why the driver would do that, the fact is that this is a feature we support and it's a part of the API. NBD uses it, for instance. Your patch breaks it, for saving a bit of memory. So I will not include it. -- Jens Axboe
