On 12/07/2020 18:59, Jens Axboe wrote: > On 7/12/20 3:41 AM, Pavel Begunkov wrote: >> Make io_kiocb slimmer by 24 bytes mainly by revising lists usage. The >> drawback is adding extra kmalloc in draining path, but that's a slow >> path, so meh. It also frees some space for the deferred completion path >> if would be needed in the future, but the main idea here is to shrink it >> to 3 cachelines in the end. >> >> I'm not happy yet with a few details, so that's not final, but it would >> be lovely to hear some feedback. > > I think it looks pretty good, most of the changes are straight forward. > Adding a completion entry that shares the submit space is a good idea, > and really helps bring it together. > > From a quick look, the only part I'm not super crazy about is patch #3. Thanks! > I'd probably rather use a generic list name and not unionize the tw > lists. I don't care much, but without compiler's help always have troubles finding and distinguishing something as generic as "list". BTW, I thought out how to bring it down to 3 cache lines, but that would require taking io_wq_work out of io_kiocb and kmalloc'ing it on demand. And there should also be a bunch of nice side effects like improving apoll. -- Pavel Begunkov
