On Fri, Sep 10, 2021 at 07:57:49AM -0600, Jens Axboe wrote: > It was just a quick hack, might very well be too eager to go through > those motions. But pondering this instead of sleeping, we don't need to > copy all of iov_iter in order to restore the state, and we can use the > same advance after restoring. So something like this may be more > palatable. Caveat - again untested, and I haven't tested the performance > impact of this at all. You actually can cut it down even more - nr_segs + iov remains constant all along, so you could get away with just 3 words here... I would be surprised if extra memory traffic had shown up - it's well within the noise from register spills, (un)inlining, etc. We are talking about 3 (or 4, with your variant) extra words on one stack frame (and that'd be further offset by removal of ->truncated); I'd still like to see the profiling data, but concerns about extra memory traffic due to that are, IMO, misplaced.
