Messages in this thread | | | From | "Zengtao (B)" <> | Subject | RE: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer | Date | Thu, 2 Jan 2020 03:05:40 +0000 |
| |
Hi Sudeep:
Thanks for your reply.
> -----Original Message----- > From: Sudeep Holla [mailto:sudeep.holla@arm.com] > Sent: Wednesday, January 01, 2020 12:41 AM > To: Zengtao (B) > Cc: Linuxarm; Greg Kroah-Hartman; Rafael J. Wysocki; > linux-kernel@vger.kernel.org; Sudeep Holla; Morten Rasmussen > Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts > with lower layer > > On Mon, Dec 23, 2019 at 04:16:19PM +0800, z00214469 wrote: > > As we know, from sched domain's perspective, the DIE layer should be > > larger than or at least equal to the MC layer, and in some cases, MC > > is defined by the arch specified hardware, MPIDR for example, but > NUMA > > can be defined by users, > > Who are the users you are referring above ? For example, when I use QEMU to start a guest linux, I can define the NUMA topology of the guest linux whatever i want. > > with the following system configrations: > > Do you mean ACPI tables or DT or some firmware tables ? > > > ************************************* > > NUMA: 0-2, 3-7 > > Is the above simply wrong with respect to hardware and it actually match > core_siblings ? > Actually, we can't simply say this is wrong, i just want to show an example. And this example also can be: NUMA: 0~23, 24~47 core_siblings: 0-15, 16-31, 32~47
> > core_siblings: 0-3, 4-7 > > ************************************* > > Per the current code, for core 3, its MC cpu map fallbacks to 3~7(its > > core_sibings is 0~3 while its numa node map is 3~7). > > > > For the sched MC, when we are build sched groups: > > step1. core3 's sched groups chain is built like this: 3->4->5->6->7->3 > > step2. core4's sched groups chain is built like this: 4->5->6->7->4 > > so after step2, core3's sched groups for MC level is overlapped, more > > importantly, it will fall to dead loop if while(sg != sg->groups) > > > > Obviously, the NUMA node with cpu 3-7 conflict with the MC level cpu > > map, but unfortunately, there is no way even detect such cases. > > > > Again, is cpu 3-7 actually in a NUMA node or is it 4-7 ? > > > In this patch, prompt a warning message to help with the above cases. > > > > Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com> > > --- > > drivers/base/arch_topology.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > > index 1eb81f11..5fe44b3 100644 > > --- a/drivers/base/arch_topology.c > > +++ b/drivers/base/arch_topology.c > > @@ -439,10 +439,18 @@ const struct cpumask > *cpu_coregroup_mask(int cpu) > > if (cpumask_subset(&cpu_topology[cpu].core_sibling, core_mask)) { > > /* not numa in package, lets use the package siblings */ > > core_mask = &cpu_topology[cpu].core_sibling; > > - } > > + } else > > + pr_warn_once("Warning: suspicous broken topology: cpu:[%d]'s > core_sibling:[%*pbl] not a subset of numa node:[%*pbl]\n", > > + cpu, cpumask_pr_args(&cpu_topology[cpu].core_sibling), > > + cpumask_pr_args(core_mask)); > > + > > Won't this print warning on all systems that don't have numa within a > package ? What are you trying to achieve here ?
Since in my case, when this corner case happens, the linux kernel just fall into dead loop with no prompt, here this is a helping message will help a lot.
> > > if (cpu_topology[cpu].llc_id != -1) { > > if (cpumask_subset(&cpu_topology[cpu].llc_sibling, core_mask)) > > core_mask = &cpu_topology[cpu].llc_sibling; > > + else > > + pr_warn_once("Warning: suspicous broken topology: > cpu:[%d]'s llc_sibling:[%*pbl] not a subset of numa node:[%*pbl]\n", > > + cpu, > cpumask_pr_args(&cpu_topology[cpu].llc_sibling), > > + cpumask_pr_args(core_mask)); > > } > > > > This will trigger warning on all systems that lack cacheinfo topology. > I don't understand the intent of this patch at all. Can you explain > all the steps you follow and the issue you face ?
Can you show me an example, what I really want to warn is the case that NUMA topology conflicts with lower level.
> > -- > Regards, > Sudeep
| |