On Sat, Nov 02, 2019 at 03:29:11PM +0800, Ming Lei wrote: > __blk_queue_split() may be a bit heavy for small block size(such as > 512B, or 4KB) IO, so introduce one flag to decide if this bio includes > multiple page. And only consider to try splitting this bio in case > that the multiple page flag is set. So, back in the day I had an alternative approach in mind: get rid of blk_queue_split entirely, by pushing splitting down to the request layer - when we map the bio/request to sgl, just have it map as much as will fit in the sgl and if it doesn't entirely fit bump bi_remaining and leave it on the request queue. This would mean there'd be no need for counting segments at all, and would cut a fair amount of code out of the io path.
