+ Arnd, Linus On Fri, 12 Jan 2024 at 15:22, Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 1/11/24 10:44 PM, Christoph Hellwig wrote: > > On Thu, Jan 11, 2024 at 01:06:43PM -0700, Jens Axboe wrote: > >> Something like this? Not super pretty with the duplication, but... > >> Should suffice for a fix, and then we can refactor it on top of that. > >> ioprio is inherited when cloning, so we don't need to do that post the > >> split. > > > > Yes, this could work. It'll get worse with anything we need to do under > > q_usage_counter counter, though. I mean, it is a perpcu_counter, which > > should be really light-weight compared to all the other stuff you do. > > I'd really love to see numbers that show it matters. > > Yep it is pretty cheap, but it's not free. Here's a test where we just > grab a ref and drop it, which should arguably be cheaper than doing a > ref at the top and dropping it at the bottom due to temporal locality: > > 5.01% +0.86% [kernel.vmlinux] [k] blk_mq_submit_bio > > >> Should > >> be set at init time and then never change. And agree would be so nice to > >> kill that code... > > > > I wish we could see some more folks from the mmc maintainers to do > > proper scatterlist (or bio/request) kmap helpers. The scsi drivers > > could easily piggy back on that or just be disabled for HIGHMEM configs. > > Maybe we just nudge them that way by making them depend on !HIGHMEM... > > -- > Jens Axboe > Not sure exactly what problem you are trying to solve here, but I am certainly happy to help, if I can. Can you perhaps point me to a couple of drivers that need to be converted? Kind regards Uffe
