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@xxxxxxxxxxxxxxx> 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@xxxxxxxxx/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 just matching what is in Linus's tree, if it's wrong here, in a stable tree, it should be wrong there too. If not, please explain why not? thanks, greg k-h
