Hello Vincent, sorry to resurrect this thread again, I was trying to backport this patch and corresponding fixes to our Ubuntu 4.15 kernel [1] to fix an issue report by LTP cfs_bandwidth01 test[2], my colleague Guilherme told me there once a discussion about backporting this on this thread. You mentioned here this should not be backported to earlier stable kernel, I am curious if there is any specific reason of it? Too risky maybe? Thanks! PHLin [1] https://lists.ubuntu.com/archives/kernel-team/2021-June/121571.html [2] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/sched/cfs-scheduler/cfs_bandwidth01.c On Thu, Nov 19, 2020 at 9:25 PM Vincent Guittot <vincent.guittot@xxxxxxxxxx> wrote: > > On Thu, 19 Nov 2020 at 12:36, Guilherme G. Piccoli > <gpiccoli@xxxxxxxxxxxxx> wrote: > > > > > > > > On 19/11/2020 05:36, Vincent Guittot wrote: > > > On Thu, 19 Nov 2020 at 01:36, Tao Zhou <t1zhou@xxxxxxx> wrote: > > >> > > >> On Thu, Nov 19, 2020 at 07:50:15AM +0800, Tao Zhou wrote: > > >>> On Wed, Nov 18, 2020 at 07:56:38PM -0300, Guilherme G. Piccoli wrote: > > >>>> Hi Vincent (and all CCed), I'm sorry to ping about such "old" patch, but > > >>>> we experienced a similar condition to what this patch addresses; it's an > > >>>> older kernel (4.15.x) but when suggesting the users to move to an > > >>>> updated 5.4.x kernel, we noticed that this patch is not there, although > > >>>> similar ones are (like [0] and [1]). > > >>>> > > >>>> So, I'd like to ask if there's any particular reason to not backport > > >>>> this fix to stable kernels, specially the longterm 5.4. The main reason > > >>>> behind the question is that the code is very complex for non-experienced > > >>>> scheduler developers, and I'm afraid in suggesting such backport to 5.4 > > >>>> and introduce complex-to-debug issues. > > >>>> > > >>>> Let me know your thoughts Vincent (and all CCed), thanks in advance. > > >>>> Cheers, > > >>>> > > >>>> > > >>>> Guilherme > > >>>> > > >>>> > > >>>> P.S. For those that deleted this thread from the email client, here's a > > >>>> link: > > >>>> https://lore.kernel.org/lkml/20200513135528.4742-1-vincent.guittot@xxxxxxxxxx/ > > >>>> > > >>>> > > >>>> [0] > > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fe61468b2cb > > >>>> > > >>>> [1] > > >>>> https://lore.kernel.org/lkml/20200506141821.GA9773@xxxxxxxxxxxxxxxxxxxxxxxxx/ > > >>>> <- great thread BTW! > > >>> > > >>> 'sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list" failed to apply to > > >>> 5.4-stable tree' > > >>> > > >>> You could check above. But I do not have the link about this. Can't search it > > >>> on LKML web: https://lore.kernel.org/lkml/ > > >>> > > >>> BTW: 'ouwen210@xxxxxxxxxxx' and 'zohooouoto@xxxxxxxxxxx' all is myself. > > >>> > > >>> Sorry for the confusing.. > > >>> > > >>> Thanks. > > >> > > >> Sorry again. I forget something. It is in the stable. > > >> > > >> Here it is: > > >> > > >> https://lore.kernel.org/stable/159041776924279@xxxxxxxxx/ > > > > > > I think it has never been applied to stable. > > > As you mentioned, the backport has been sent : > > > https://lore.kernel.org/stable/20200525172709.GB7427@vingu-book/ > > > > > > I received another emailed in September and pointed out to the > > > backport : https://www.spinics.net/lists/stable/msg410445.html > > > > > > > > >> > > > > Thanks a lot Tao and Vincent! Nice to know that you already worked the > > backport, gives much more confidence when the author does that heheh > > > > So, this should go to stable 5.4.y, but not 4.19.y IIUC? > > Yeah. they should be backported up to v5.1 but not earlier > > Regards, > Vincent > > > Cheers, > > > > > > Guilherme
