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Date: Wed, 16 Feb 2022 02:38:27 +0000
From: "tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>
To: 'Reinette Chatre' <reinette.chatre@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
Shuah Khan <shuah@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: RE: [PATCH v2] selftests/resctrl: Print a message if the result of
MBM&CMT tests is failed when Intel Sub-NUMA is enabled
Hi Reinette,
> On 1/21/2022 12:00 AM, tan.shaopeng@...itsu.com wrote:
> > Hi Reinette,
> >
> >> On 12/13/2021 2:03 AM, Shaopeng Tan wrote:
> >>> If the result of MBM&CMT tests is failed when Intel Sub-NUMA is
> >>> enabled, print a possible causes of failure.
> >>> Since when the Intel Sub-NUMA Clustering(SNC) feature is enabled,
> >>> the CMT and MBM counters may not be accurate.
> >>>
> >>> Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> >>> ---
> >>> 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 2nd Generation Intel Xeon
> >>> Scalable Processor, the result may be "not ok".
> >>> If result of MBM&CMT tests is failed when Intel Sub-NUMA is enabled,
> >>> fix it to print a possible cause of failure, instead of SKIP these
> >>> tests in v1.
> >>>
> >>> Thanks,
> >>>
> >>> tools/testing/selftests/resctrl/Makefile | 1 +
> >>> tools/testing/selftests/resctrl/cmt_test.c | 5 ++-
> >>> tools/testing/selftests/resctrl/mbm_test.c | 5 ++-
> >>> tools/testing/selftests/resctrl/resctrl.h | 2 ++
> >>> .../testing/selftests/resctrl/resctrl_tests.c | 36
> >> +++++++++++++++++++
> >>> tools/testing/selftests/resctrl/resctrlfs.c | 26 ++++++++++++++
> >>> 6 files changed, 73 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/tools/testing/selftests/resctrl/Makefile
> >>> b/tools/testing/selftests/resctrl/Makefile
> >>> index adfd92145e12..6d257f40e6ac 100644
> >>> --- a/tools/testing/selftests/resctrl/Makefile
> >>> +++ b/tools/testing/selftests/resctrl/Makefile
> >>> @@ -1,6 +1,7 @@
> >>> #SPDX-License-Identifier: GPL-2.0
> >>>
> >>> CFLAGS += -g -Wall -O2 -D_FORTIFY_SOURCE=2
> >>> +LDLIBS += -lnuma
> >>>
> >>> TEST_GEN_PROGS := resctrl_tests
> >>> EXTRA_SOURCES := $(wildcard *.c)
> >>> diff --git a/tools/testing/selftests/resctrl/cmt_test.c
> >>> b/tools/testing/selftests/resctrl/cmt_test.c
> >>> index 8968e36db99d..c5a49444c5a0 100644
> >>> --- a/tools/testing/selftests/resctrl/cmt_test.c
> >>> +++ b/tools/testing/selftests/resctrl/cmt_test.c
> >>> @@ -136,8 +136,11 @@ int cmt_resctrl_val(int cpu_no, int n, char
> >> **benchmark_cmd)
> >>> return ret;
> >>>
> >>> ret = check_results(¶m, n);
> >>> - if (ret)
> >>> + if (ret) {
> >>> + if (sub_numa_cluster_enable)
> >>> + ksft_print_msg("Sub-NUMA Clustering(SNC) feature
> >> is enabled, the
> >>> +CMT counters may not be accurate.\n");
> >>> return ret;
> >>> + }
> >>>
> >>> cmt_test_cleanup();
> >>>
> >>> diff --git a/tools/testing/selftests/resctrl/mbm_test.c
> >>> b/tools/testing/selftests/resctrl/mbm_test.c
> >>> index 8392e5c55ed0..7dc1bdf2d0b8 100644
> >>> --- a/tools/testing/selftests/resctrl/mbm_test.c
> >>> +++ b/tools/testing/selftests/resctrl/mbm_test.c
> >>> @@ -136,8 +136,11 @@ int mbm_bw_change(int span, int cpu_no, char
> >> *bw_report, char **benchmark_cmd)
> >>> return ret;
> >>>
> >>> ret = check_results(span);
> >>> - if (ret)
> >>> + if (ret) {
> >>> + if (sub_numa_cluster_enable)
> >>> + ksft_print_msg("Sub-NUMA Clustering(SNC) feature
> >> is enabled, the
> >>> +MBM counters may not be accurate.\n");
> >>> return ret;
> >>> + }
> >>>
> >>> mbm_test_cleanup();
> >>>
> >>> diff --git a/tools/testing/selftests/resctrl/resctrl.h
> >>> b/tools/testing/selftests/resctrl/resctrl.h
> >>> index 1ad10c47e31d..4b8ad4fbd016 100644
> >>> --- a/tools/testing/selftests/resctrl/resctrl.h
> >>> +++ b/tools/testing/selftests/resctrl/resctrl.h
> >>> @@ -76,6 +76,7 @@ extern pid_t bm_pid, ppid;
> >>>
> >>> extern char llc_occup_path[1024];
> >>> extern bool is_amd;
> >>> +extern bool sub_numa_cluster_enable;
> >>>
> >>> bool check_resctrlfs_support(void); int filter_dmesg(void); @@
> >>> -85,6 +86,7 @@ int umount_resctrlfs(void); int
> >>> validate_bw_report_request(char *bw_report); bool
> >>> validate_resctrl_feature_request(const char *resctrl_val); char
> >>> *fgrep(FILE *inf, const char *str);
> >>> +char *fgrep_last_match_line(FILE *inf, const char *str);
> >>> int taskset_benchmark(pid_t bm_pid, int cpu_no); void
> >>> run_benchmark(int signum, siginfo_t *info, void *ucontext); int
> >>> write_schemata(char *ctrlgrp, char *schemata, int cpu_no, diff --git
> >>> a/tools/testing/selftests/resctrl/resctrl_tests.c
> >>> b/tools/testing/selftests/resctrl/resctrl_tests.c
> >>> index 3be0895c492b..bbab4a7f37ed 100644
> >>> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> >>> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> >>> @@ -8,12 +8,15 @@
> >>> * Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
> >>> * Fenghua Yu <fenghua.yu@...el.com>
> >>> */
> >>> +#include <numa.h>
> >>> +#include <string.h>
> >>> #include "resctrl.h"
> >>>
> >>> #define BENCHMARK_ARGS 64
> >>> #define BENCHMARK_ARG_SIZE 64
> >>>
> >>> bool is_amd;
> >>> +bool sub_numa_cluster_enable;
> >>>
> >>> void detect_amd(void)
> >>> {
> >>> @@ -34,6 +37,35 @@ void detect_amd(void)
> >>> fclose(inf);
> >>> }
> >>>
> >>> +void check_sub_numa_cluster(void)
> >>> +{
> >>> + FILE *inf = fopen("/proc/cpuinfo", "r");
> >>> + char *res, *s;
> >>> + int socket_num = 0;
> >>> + int numa_nodes = 0;
> >>> +
> >>> + if (!inf)
> >>> + return;
> >>> +
> >>> + res = fgrep_last_match_line(inf, "physical id");
> >>> +
> >>> + if (res) {
> >>> + s = strpbrk(res, "1234567890");
> >>> + socket_num = atoi(s) + 1;
> >>> + free(res);
> >>> + }
> >>> + fclose(inf);
> >>> +
> >>> + numa_nodes = numa_max_node() + 1;
> >>> +
> >>> + /*
> >>> + * when the Sub-NUMA Clustering(SNC) feature is enabled,
> >>> + * the number of numa nodes is twice the number of sockets.
> >>> + */
> >>> + if (numa_nodes == (2 * socket_num))
> >>> + sub_numa_cluster_enable = true;
> >>> +}
> >>
> >>
> >> Unfortunately there does not seem to be an architectural way to
> >> detect if SNC has been enabled and the above test is fragile wrt the
> >> assumptions about the topology of the system. What we need is a
> >> reliable and future-proof test but I do not know what that should be.
> >
> > I understand your concerns.
> > At least I know SNC affects on the 2nd Generation Intel Xeon.
> > So, how about just printing information when the test is running on 2nd
> Generation Intel Xeon?
> > That is, when the result of MBM&CMT test is "not ok"
> > and if running cpu model is 2nd Generation Intel Xeon, then print
> > information about the possibility of failure (SNC may be enabled).
> > How about this idea?
>
> I think that making this model specific would be hard to get right for all systems
> and hard to maintain. Perhaps we could just print a generic message on failure?
> Something
> like: "Intel CMT and MBM counters may be inaccurate when Sub-NUMA
> Clustering (SNC) is enabled. Ensure SNC is disabled in the BIOS if this system
> supports SNC." I'd be the first to admit that this is not ideal and would
> appreciate suggestions for improvement. Unfortunately we seem to lack a
> reliable and future proof way to detect if SNC is enabled but I do look forward to
> being corrected.
I can't think out a better idea, I am going to use your idea.
If MBM&CMT test is running on Intel cpu and the result of MBM&CMT test is "not ok",
then print a message:
"Intel CMT and MBM counters may be inaccurate when Sub-NUMA Clustering (SNC) is enabled.
Ensure SNC is disabled in the BIOS if this system supports SNC."
Best regards,
Tan Shaopeng
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