On Mon, 24 Jan 2022, Christoph Hellwig wrote: > On Mon, Jan 24, 2022 at 02:48:32PM +1100, NeilBrown wrote: > > Code that does swap read-ahead uses blk_start_plug() and > > blk_finish_plug() to allow lower levels to combine multiple read-ahead > > pages into a single request, but calls blk_finish_plug() *before* > > submitting the original (non-ahead) read request. > > This missed an opportunity to combine read requests. > > > > This patch moves the blk_finish_plug to *after* all the reads. > > This will likely combine the primary read with some of the "ahead" > > reads, and that may slightly increase the latency of that read, but it > > should more than make up for this by making more efficient use of the > > storage path. > > > > The patch mostly makes the code look more consistent. Performance > > change is unlikely to be noticeable. > > Looks good: > > Reviewed-by: Christoph Hellwig <hch@xxxxxx> Thanks. > > > Fixes-no-auto-backport: 3fb5c298b04e ("swap: allow swap readahead to be merged") > > Is this really a thing? Maybe it should be..... As I'm sure you guessed, I think it is valuable to record this connection between commits, but I don't like it hasty automatic backporting of patches where the (unknown) risk might exceed the (known) value. This is how I choose to state my displeasure. Thanks, NeilBrown