On Wed, Jan 31, 2024 at 01:32:40PM -0800, Bart Van Assche wrote: > On 1/30/24 22:22, Christoph Hellwig wrote: > > On Mon, Jan 29, 2024 at 04:03:11PM -0800, Bart Van Assche wrote: > > > Would you agree with disabling fair sharing entirely? > > > > As far as I can tell fair sharing exists to for two reasons: > > > > 1) to guarantee each queue can actually make progress for e.g. > > memory reclaim > > 2) to not unfairly give queues and advantage over others > > > > What are you arguments that we do not need this? > > Regarding (1), isn't forward progress guaranteed by the sbitmap > implementation? The algorithm in __sbitmap_queue_wake_up() does not guarantee > perfect fairness but I think it is good enough to guarantee forward progress > of code that is waiting for a block layer tag. What if all the tags are used by one queue and all the tags are performing long running operations? Sure, sbitmap might wake up the longest waiter, but that could be hours.
