On Fri, Oct 20, 2023 at 09:17:11AM -0700, Bart Van Assche wrote: > On 10/19/23 21:41, Christoph Hellwig wrote: > > On Wed, Oct 18, 2023 at 11:00:56AM -0700, Bart Van Assche wrote: > > > Note: it has been attempted to rework this algorithm. See also "[PATCH > > > RFC 0/7] blk-mq: improve tag fair sharing" > > > (https://lore.kernel.org/linux-block/20230618160738.54385-1-yukuai1@xxxxxxxxxxxxxxx/). > > > Given the complexity of that patch series, I do not expect that patch > > > series to be merged. > > > > Work is hard, so let's skip it? That's not really the most convincing > > argument. Hey, I'm the biggest advocate for code improvement by code > > removal, but you better have a really good argument why it doesn't hurt > > anyone. > > Hi Christoph, > > No, it's not because it's hard to improve the tag fairness algorithm > that I'm proposing to skip this work. It's because I'm convinced that > an improved fairness algorithm will have a negative performance impact > that is larger than that of the current algorithm. > > Do you agree that the legacy block layer never had any such fairness > algorithm and also that nobody ever complained about fairness issues > for the legacy block layer? I think that's a strong argument in favor of > removing the fairness algorithm. The legacy block request layer didn't have a tag resource shared among multiple request queues. Each queue had their own mempool for allocating requests. The mempool, I think, would always guarantee everyone could get at least one request.
