Re: Patch "sched/fair: sanitize vruntime of entity being placed" has been added to the 4.14-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Mar 28, 2023 at 05:02:21PM +0800, Zhang Qiao wrote:
> 
> 
> 在 2023/3/7 23:23, Greg KH 写道:
> > On Mon, Mar 06, 2023 at 06:51:15PM +0800, Zhang Qiao wrote:
> >>
> >>
> >> 在 2023/3/6 18:05, Greg KH 写道:
> >>> On Mon, Mar 06, 2023 at 05:28:41PM +0800, Zhang Qiao wrote:
> >>>>
> >>>>
> >>>> 在 2023/3/6 17:19, Greg KH 写道:
> >>>>> On Mon, Mar 06, 2023 at 04:31:57PM +0800, Zhang Qiao wrote:
> >>>>>>
> >>>>>>
> >>>>>> 在 2023/3/5 12:02, Sasha Levin 写道:
> >>>>>>> This is a note to let you know that I've just added the patch titled
> >>>>>>>
> >>>>>>>     sched/fair: sanitize vruntime of entity being placed
> >>>>>>>
> >>>>>>> to the 4.14-stable tree which can be found at:
> >>>>>>>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >>>>>>>
> >>>>>>> The filename of the patch is:
> >>>>>>>      sched-fair-sanitize-vruntime-of-entity-being-placed.patch
> >>>>>>> and it can be found in the queue-4.14 subdirectory.
> >>>>>>>
> >>>>>>> If you, or anyone else, feels it should not be added to the stable tree,
> >>>>>>> please let <stable@vger.kernel.org> know about it.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> commit 38247e1de3305a6ef644404ac818bc6129440eae
> >>>>>>
> >>>>>> Hi,
> >>>>>> This patch has significant impact on the hackbench.throughput [1].
> >>>>>> Please don't backport this patch.
> >>>>>>
> >>>>>> [1] https://lore.kernel.org/lkml/202302211553.9738f304-yujie.liu@intel.com/T/#u
> >>>>>
> >>>>> This link says it made hackbench.throughput faster, not slower, so why
> >>>>> would we NOT want it?
> >>>>
> >>>> Please see this section. In some cases, this patch reset task's vruntime by mistake and
> >>>> will lead to wrong results.
> >>>>
> >>>>
> >>>> On Tue, Feb 21, 2023 at 03:34:16PM +0800, kernel test robot wrote:
> >>>>>
> >>>>> FYI, In addition to that, the commit also has significant impact on the following tests:
> >>>>>
> >>>>> +------------------+--------------------------------------------------+
> >>>>> | testcase: change | hackbench: hackbench.throughput -8.1% regression |
> >>>>> | test machine     | 104 threads 2 sockets (Skylake) with 192G memory |
> >>>>> | test parameters  | cpufreq_governor=performance                     |
> >>>>> |                  | ipc=socket                                       |
> >>>>> |                  | iterations=4                                     |
> >>>>> |                  | mode=process                                     |
> >>>>> |                  | nr_threads=100%                                  |
> >>>>> +------------------+--------------------------------------------------+
> >>>>>
> >>>>> Details are as below:
> >>>
> >>> So one benchmark did better, by a lot, and one did less, by a little?
> >>> Which one matters "more">
> >>>
> >>> So Linus's tree now has a regression?  Or not?  I'm confused.  We are
> >>
> >> Yes, Linus's tree also has a regression, and i have sent a patch[1] for fix this regression.
> >>
> >>
> >> [1]: https://lore.kernel.org/lkml/79850642-ebac-5c23-d32d-b28737dcb91e@huawei.com/
> >>
> >> thanks.
> >> Zhang qiao.
> > 
> > Ok, I've dropped this from all stable queues now.  Please let us know
> > when we can pick it up again and what the fixup commit id in Linus's
> > tree is when it lands there.
> 
> Hi,
> 
> The fixup patch has been merged into Linus's tree, its commit id is:
> a53ce18cacb477dd0513c607f187d16f0fa96f71 ("sched/fair: Sanitize vruntime of entity being migrated")

Wonderful, I have queued both of these up now, thank you for letting me
know.

greg k-h