On Thu, May 24, 2018 at 12:06 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, May 24, 2018 at 10:27:59AM -0700, Hugh Dickins wrote: > > On Thu, May 24, 2018 at 4:28 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > On Thu, May 24, 2018 at 04:17:12AM -0700, Hugh Dickins wrote: > > > > Thu, May 24, 2018 at 4:06 AM Greg Kroah-Hartman > > > > <gregkh@xxxxxxxxxxxxxxxxxxx> > > > > wrote: > > > > > > > > > On Thu, May 24, 2018 at 12:50:11PM +0200, Jan Kara wrote: > > > > > > On Thu 24-05-18 11:38:27, Greg Kroah-Hartman wrote: > > > > > > > 4.4-stable review patch. If anyone has any objections, please > > let me > > > > know. > > > > > > > > > > > > Just one objection: Why does stable care about this (and the > > previous > > > > > > patch)? I've checked the stable queue and I don't see anything that > > > > would > > > > > > have these patches as a prerequisite. And on their own, they are > > only > > > > > > cleanups without substantial gains. > > > > > > > > > There's a small gain here: > > > > > > > > > > > paralleldd > > > > > > > 4.4.0 4.4.0 > > > > > > > vanilla avoidlock > > > > > > > Amean Elapsd-1 5.28 ( 0.00%) 5.15 ( 2.50%) > > > > > > > Amean Elapsd-4 5.29 ( 0.00%) 5.17 ( 2.12%) > > > > > > > Amean Elapsd-7 5.28 ( 0.00%) 5.18 ( 1.78%) > > > > > > > Amean Elapsd-12 5.20 ( 0.00%) 5.33 ( -2.50%) > > > > > > > Amean Elapsd-21 5.14 ( 0.00%) 5.21 ( -1.41%) > > > > > > > Amean Elapsd-30 5.30 ( 0.00%) 5.12 ( 3.38%) > > > > > > > Amean Elapsd-48 5.78 ( 0.00%) 5.42 ( 6.21%) > > > > > > > Amean Elapsd-79 6.78 ( 0.00%) 6.62 ( 2.46%) > > > > > > > Amean Elapsd-110 9.09 ( 0.00%) 8.99 ( 1.15%) > > > > > > > Amean Elapsd-128 10.60 ( 0.00%) 10.43 ( 1.66%) > > > > > > > > > > > > > > The impact is small but intuitively, it makes sense to avoid > > > > unnecessary > > > > > > > calls to lock_page. > > > > > > > > > Yes, it's small, but it's marked in the SLES kernel as "needs to be > > > > > merged into stable", so obviously it matters to someone :) > > > > > > > > Hmm. I had the same reaction to these two as Jan, but assumed that they > > > > made applying later patches easier, and didn't take the trouble he did > > to > > > > find that's not so. > > > > > > > > I've no wish to be disputatious, but it does seem that the definition of > > > > "stable" has changed, and not necessarily for the better, if it's now a > > > > home for small gains: I thought we left those to upstream. > > > > > This is in the SLES kernel for a reason, and again, it's in the section > > > that says "this should be pushed to stable". So if it's good enough for > > > the SLES kernel, why isn't it good enough for all users of this kernel > > > tree? > > > > > If you all think it should be dropped in both places, that's fine with > > > me :) > > > > I think they are perfectly fine in SLES: folding in good work is a part of > > what distros are about. > And it's also what stable is for. We have had backports of performance > improvements in the past, along with lots of other things over the > years. This is a performance improvement. A tiny one, yes, but getting > rid of a lock is a good thing, and I picked it up as part of my review > of what a distro decided was worth adding for their users, as that's a > huge signal that might be of value to others. > > But I cannot find anything in stable-kernel-rules.rst that would admit them > > - perhaps that's just out of date? > Nope, that's the list I use to say "no" to. You can't describe > everything in that file, it's a judgement call. > > If -stable is to be a compendium of "this looks nice, you might like to > > include it", so be it: but the rules should then be updated. > This is a "a bunch of people I trust took it in their kernel, and it's > been running on zillion of machines for a while and causes no harm and a > slight benefit, so let's add it!" type of thing. It's not the only > patch in this series that was like that, but for some reason this one is > the one the triggered the debate, which is funny to me as this does have > numbers in it showing that it is an improvement :) Thank you for looking after the -stable trees: please let me not waste your time any further. I have no specific objection to the two patches, which are certainly not egregious offenders. But I do still find the disconnect between stable-kernel-rules.rst and reality confusing - or perhaps I just find reality confusing :) Hugh
