On Wed, 24 Mar 2021 16:13:48 -0600 Jens Axboe <axboe@xxxxxxxxx> wrote: > On 3/24/21 4:02 PM, Andrew Morton wrote: > > On Wed, 24 Mar 2021 13:48:08 -0600 Jens Axboe <axboe@xxxxxxxxx> wrote: > > > >> On Tue, Mar 2, 2021 at 4:43 PM <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > >>> > >>> > >>> The patch titled > >>> Subject: mm: provide filemap_range_needs_writeback() helper > >>> has been added to the -mm tree. Its filename is > >>> mm-provide-filemap_range_needs_writeback-helper.patch > >> > >> Are you still planning on flushing this out for 5.12?? > > > > Oh. No, I wasn't planning on that. I saw nothing which made me think > > it was that urgent. > > Ehm ok, I think that was the plan though when we originally talked about > this series. At least that was what was in my original emails on this > topic :-) > > > What is the justification? How much performance benefit are we talking > > here? > > Well it's pretty huge, since if we return "nope can't do this > non-blocking" it'll mean that io_uring has to bump the operation to an > async threads. So CPU cost goes way up, and latencies does too. > > Problem is, we're now at -rc4, and it was my understanding that we'd get > this in for 5.12, but obviously way sooner than this. But I kind of lost > track when it went into your tree, until I started thinking about it > earlier today. While it's not the end of the world to wait for 5.13, > though the current situation does suck a lot for certain workloads. I'd be OK with sending it to Linus now, but we really should put some numbers behind "suck a lot" to justify it. And a -stable backport might be justified if the benefit is large enough, and if "certain workloads" are common enough. But with what have here, I and everyone else who considers these patches is going in blind!
