Hi Reinette,
-----Original Message----- From: Reinette Chatre reinette.chatre@intel.com Sent: Monday, March 9, 2020 2:45 PM To: Prakhya, Sai Praneeth sai.praneeth.prakhya@intel.com; shuah@kernel.org; linux-kselftest@vger.kernel.org Cc: tglx@linutronix.de; mingo@redhat.com; bp@alien8.de; Luck, Tony tony.luck@intel.com; babu.moger@amd.com; james.morse@arm.com; Shankar, Ravi V ravi.v.shankar@intel.com; Yu, Fenghua fenghua.yu@intel.com; x86@kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH V1 01/13] selftests/resctrl: Fix feature detection
Hi Sai,
On 3/6/2020 7:40 PM, Sai Praneeth Prakhya wrote:
From: Reinette Chatre reinette.chatre@intel.com
The intention of the resctrl selftests is to only run the tests associated with the feature(s) supported by the platform. Through parsing of the feature flags found in /proc/cpuinfo it is possible to learn which features are supported by the plaform.
There are currently two issues with the platform feature detection that together result in tests always being run, whether the platform supports a feature or not. First, the parsing of the the feature flags loads the line containing the flags in a buffer that is too small (256 bytes) to always contain all flags. The consequence is that the flags of the features being tested for may not be present in the buffer. Second, the actual test for presence of a feature has an error in the logic, negating the test for a particular feature flag instead of testing for the presence of a particular feature flag.
These two issues combined results in all tests being run on all platforms, whether the feature is supported or not.
Fix these issue by (1) increasing the buffer size being used to parse the feature flags, and (2) change the logic to test for presence of the feature being tested for.
Signed-off-by: Reinette Chatre reinette.chatre@intel.com Signed-off-by: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com
tools/testing/selftests/resctrl/resctrlfs.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c index 19c0ec4045a4..226dd7fdcfb1 100644 --- a/tools/testing/selftests/resctrl/resctrlfs.c +++ b/tools/testing/selftests/resctrl/resctrlfs.c @@ -596,11 +596,11 @@ bool check_resctrlfs_support(void)
char *fgrep(FILE *inf, const char *str) {
- char line[256]; int slen = strlen(str);
char line[2048];
while (!feof(inf)) {
if (!fgets(line, 256, inf))
if (!fgets(line, 2048, inf)) break;@@ -631,7 +631,7 @@ bool validate_resctrl_feature_request(char
*resctrl_val)
if (res) { char *s = strchr(res, ':');
found = s && !strstr(s, resctrl_val);
found = s && strstr(s, resctrl_val);Please note that this is only a partial fix. The current feature detection relies on the feature flags found in /proc/cpuinfo. Quirks and kernel boot parameters are not taken into account. This fix only addresses the parsing of feature flags. If a feature has been disabled via kernel boot parameter or quirk then the resctrl tests would still attempt to run the test for it.
That's a good point and makes sense to me. I think we could fix it in two ways 1. grep for strings in dmesg but that will still leave ambiguity in deciding b/w mbm and cqm because kernel prints "resctrl: L3 monitoring detected" for both the features 2. Check in "info" directory a. For cat_l3, we could search for info/L3 b. For mba, we could search for info/MB c. For cqm and mbm, we could search for specified string in info/L3_MON/mon_features
I think option 2 might be better because it can handle all cases, please let me know what you think.
Regards, Sai