Hi Shaopeng Tan,
On 11/14/2021 11:11 PM, tan.shaopeng@xxxxxxxxxxx wrote:
Hi Reinette,
On 11/10/2021 12:27 AM, Shaopeng Tan wrote:
From: "Tan, Shaopeng" <tan.shaopeng@xxxxxxxxxxxxxx>
When the Intel Sub-NUMA Clustering(SNC) feature is enabled,
the CMT and MBM counters may not be accurate.
In this case, skip MBM&CMT tests.
Signed-off-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx>
---
Hello,
According to the Intel RDT reference Manual,
when the sub-numa clustering feature is enabled, the CMT and MBM
counters may not be accurate.
When running CMT tests and MBM tests on Intel processor, the result is "not
ok".
So, fix it to skip the CMT & MBM test When the Intel Sub-NUMA
Clustering(SNC) feature is enabled.
It is not clear to me which exact document you refer to but I did find a
RDT reference manual at the link below that describes the problem you
mention:
https://www.intel.com/content/dam/develop/external/us/en/documents/18
0115-intel-rdtcascadelake-serverreferencemanual-806717.pdf
Yes, I referred this manual.
What is not mentioned in your description is that this is a hardware
errata so the test is expected to fail on these systems and I find that
disabling the test for all systems based on this hardware errata is too
drastic.
Understood. It is not reasonable to disable the test for all systems
based on this hardware errata.
When I run restrl_test on Intel(R) Xeon(R) Gold 6254 CPU,
the result of CMT & MBM is "not ok", and I took some time to debug it.
In order to other people can do the test smoothly, I'd like to update the
patch to disable the test only on 2nd Generation Intel Xeon scalable processors.
I've been thinking about this some more and I do not think that the test
should be disabled. There is a clear incompatibility between SNC and RDT
on these systems and I do not think the test should hide that, indeed it
is helpful to highlight that there is an issue. Even so, spending time
to debug a known issue is not a good use of time. Instead of skipping
the test on these systems could the test perhaps be improved to provide
more information on failure to help user decide if they really need SNC
enabled? The test would show that RDT cannot be used on their system
with the SNC configuration, hiding that information by skipping the test
may create false idea that RDT is working with that configuration.
Reinette
