[PATCH v3 0/3] selftests/resctrl: Add dynamic linked list management for IMC counters

[PATCH v3 0/3] selftests/resctrl: Add dynamic linked list management for IMC counters

[Yifan Wu]

Hi all,

This patch series introduces dynamic linked list management for IMC
counters, enabling the tests to use all available counters detected by
hardware instead of a fixed upper limit, without the need for array
bounds checking.

This series is based on Reinette's patch series aimed at fixing the
resctrl tests, available at:
https://lore.kernel.org/lkml/cover.1775266384.git.reinette.chatre@intel.com/

Changes in v3:
- Rename functions and update comments.
- Split the patches into incremental changes.
- Explicitly release memory after failing to parse the imc config.

Changes in v2:
- Fix code style and variable names.
- Integrate linked list initialization and cleanup into patch 1.
- Split the conversion from arrays to linked list across the remaining
  patches.
- Remove the IMC count and the global imcs variable.

v2: https://lore.kernel.org/all/20260410093352.3988125-1-wuyifan50@huawei.com/
v1: https://lore.kernel.org/all/20260324125034.1509177-1-wuyifan50@huawei.com/

Yifan Wu (3):
  selftests/resctrl: Introduce linked list management for IMC counters
  selftests/resctrl: Replace counter index references with pointers
  selftests/resctrl: Enable dynamic management of IMC counters via
    linked list

 tools/testing/selftests/resctrl/mba_test.c    |   1 +
 tools/testing/selftests/resctrl/mbm_test.c    |   1 +
 tools/testing/selftests/resctrl/resctrl.h     |   2 +
 tools/testing/selftests/resctrl/resctrl_val.c | 160 ++++++++++--------
 4 files changed, 91 insertions(+), 73 deletions(-)

-- 
2.34.1

[PATCH v3 1/3] selftests/resctrl: Introduce linked list management for IMC counters

[Yifan Wu]

The static array approach to managing IMC counters has fixed size
constraints and limited compatibility and scalability. Introduce
a linked list-based dynamic management infrastructure to address
these limitations. Add the core data structure definitions and
memory allocation and cleanup functions for dynamic counter
configurations.

Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
---
 tools/testing/selftests/resctrl/mba_test.c    |  1 +
 tools/testing/selftests/resctrl/mbm_test.c    |  1 +
 tools/testing/selftests/resctrl/resctrl.h     |  2 ++
 tools/testing/selftests/resctrl/resctrl_val.c | 27 +++++++++++++++++--
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index 39cee9898359..4bb1a82eb195 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -166,6 +166,7 @@ static int check_results(void)
 
 static void mba_test_cleanup(void)
 {
+	cleanup_read_mem_bw_imc();
 	remove(RESULT_FILE_NAME);
 }
 
diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 6dbbc3b76003..68c89f50a34a 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -125,6 +125,7 @@ static int mbm_measure(const struct user_params *uparams,
 
 static void mbm_test_cleanup(void)
 {
+	cleanup_read_mem_bw_imc();
 	remove(RESULT_FILE_NAME);
 }
 
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 175101022bf3..a7556cdae0de 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -24,6 +24,7 @@
 #include <linux/perf_event.h>
 #include <linux/compiler.h>
 #include <linux/bits.h>
+#include <linux/list.h>
 #include "kselftest.h"
 
 #define MB			(1024 * 1024)
@@ -183,6 +184,7 @@ void mem_flush(unsigned char *buf, size_t buf_size);
 void fill_cache_read(unsigned char *buf, size_t buf_size, bool once);
 ssize_t get_fill_buf_size(int cpu_no, const char *cache_type);
 int initialize_read_mem_bw_imc(void);
+void cleanup_read_mem_bw_imc(void);
 int measure_read_mem_bw(const struct user_params *uparams,
 			struct resctrl_val_param *param, pid_t bm_pid);
 void initialize_mem_bw_resctrl(const struct resctrl_val_param *param,
diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index f20d2194c35f..a72dc4ae61fe 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -28,6 +28,7 @@ struct membw_read_format {
 };
 
 struct imc_counter_config {
+	struct list_head entry;
 	__u32 type;
 	__u64 event;
 	__u64 umask;
@@ -38,6 +39,7 @@ struct imc_counter_config {
 static char mbm_total_path[1024];
 static int imcs;
 static struct imc_counter_config imc_counters_config[MAX_IMCS];
+LIST_HEAD(imc_counters_list);
 static const struct resctrl_test *current_test;
 
 static void read_mem_bw_initialize_perf_event_attr(int i)
@@ -113,6 +115,7 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 				    unsigned int *count)
 {
 	char imc_events_dir[PATH_MAX], imc_counter_cfg[PATH_MAX];
+	struct imc_counter_config *imc_counter;
 	unsigned int orig_count = *count;
 	char cas_count_cfg[1024];
 	struct dirent *ep;
@@ -126,13 +129,13 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 			    imc_dir);
 	if (path_len >= sizeof(imc_events_dir)) {
 		ksft_print_msg("Unable to create path to %sevents\n", imc_dir);
-		return -1;
+		goto out;
 	}
 
 	dp = opendir(imc_events_dir);
 	if (!dp) {
 		ksft_perror("Unable to open PMU events directory");
-		return -1;
+		goto out;
 	}
 
 	while ((ep = readdir(dp))) {
@@ -167,11 +170,17 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 			ksft_print_msg("Maximum iMC count exceeded\n");
 			goto out_close;
 		}
+		imc_counter = calloc(1, sizeof(*imc_counter));
+		if (!imc_counter) {
+			ksft_perror("Unable to allocate memory for iMC counters");
+			goto out_close;
+		}
 
 		imc_counters_config[*count].type = type;
 		get_read_event_and_umask(cas_count_cfg, *count);
 		/* Do not fail after incrementing *count. */
 		*count += 1;
+		list_add(&imc_counter->entry, &imc_counters_list);
 	}
 	if (*count == orig_count) {
 		ksft_print_msg("Unable to find events in %s\n", imc_events_dir);
@@ -180,6 +189,10 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 	ret = 0;
 out_close:
 	closedir(dp);
+out:
+	if (ret)
+		cleanup_read_mem_bw_imc();
+
 	return ret;
 }
 
@@ -303,6 +316,16 @@ int initialize_read_mem_bw_imc(void)
 	return 0;
 }
 
+void cleanup_read_mem_bw_imc(void)
+{
+	struct imc_counter_config *imc_counter, *tmp;
+
+	list_for_each_entry_safe(imc_counter, tmp, &imc_counters_list, entry) {
+		list_del(&imc_counter->entry);
+		free(imc_counter);
+	}
+}
+
 static void perf_close_imc_read_mem_bw(void)
 {
 	int mc;
-- 
2.34.1

Re: [PATCH v3 1/3] selftests/resctrl: Introduce linked list management for IMC counters

[Reinette Chatre]

Hi Yifan,

On 5/22/26 2:05 AM, Yifan Wu wrote:
> The static array approach to managing IMC counters has fixed size
> constraints and limited compatibility and scalability. Introduce
> a linked list-based dynamic management infrastructure to address
> these limitations. Add the core data structure definitions and
> memory allocation and cleanup functions for dynamic counter
> configurations.
> 
> Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
> ---

Thank you.

Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reinette

[PATCH v3 2/3] selftests/resctrl: Replace counter index references with pointers

[Yifan Wu]

Replace direct counter number references with pointers to remove the
dependency on fixed array indexing and enable the use of different
data structures for counter management.

Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
---
 tools/testing/selftests/resctrl/resctrl_val.c | 62 +++++++++----------
 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index a72dc4ae61fe..3d2b6919717a 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -42,40 +42,40 @@ static struct imc_counter_config imc_counters_config[MAX_IMCS];
 LIST_HEAD(imc_counters_list);
 static const struct resctrl_test *current_test;
 
-static void read_mem_bw_initialize_perf_event_attr(int i)
+static void read_mem_bw_initialize_perf_event_attr(struct imc_counter_config *imc_counter)
 {
-	memset(&imc_counters_config[i].pe, 0,
+	memset(&imc_counter->pe, 0,
 	       sizeof(struct perf_event_attr));
-	imc_counters_config[i].pe.type = imc_counters_config[i].type;
-	imc_counters_config[i].pe.size = sizeof(struct perf_event_attr);
-	imc_counters_config[i].pe.disabled = 1;
-	imc_counters_config[i].pe.inherit = 1;
-	imc_counters_config[i].pe.exclude_guest = 0;
-	imc_counters_config[i].pe.config =
-		imc_counters_config[i].umask << 8 |
-		imc_counters_config[i].event;
-	imc_counters_config[i].pe.sample_type = PERF_SAMPLE_IDENTIFIER;
-	imc_counters_config[i].pe.read_format =
+	imc_counter->pe.type = imc_counter->type;
+	imc_counter->pe.size = sizeof(struct perf_event_attr);
+	imc_counter->pe.disabled = 1;
+	imc_counter->pe.inherit = 1;
+	imc_counter->pe.exclude_guest = 0;
+	imc_counter->pe.config =
+		imc_counter->umask << 8 |
+		imc_counter->event;
+	imc_counter->pe.sample_type = PERF_SAMPLE_IDENTIFIER;
+	imc_counter->pe.read_format =
 		PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING;
 }
 
-static void read_mem_bw_ioctl_perf_event_ioc_reset_enable(int i)
+static void read_mem_bw_ioctl_perf_event_ioc_reset_enable(struct imc_counter_config *imc_counter)
 {
-	ioctl(imc_counters_config[i].fd, PERF_EVENT_IOC_RESET, 0);
-	ioctl(imc_counters_config[i].fd, PERF_EVENT_IOC_ENABLE, 0);
+	ioctl(imc_counter->fd, PERF_EVENT_IOC_RESET, 0);
+	ioctl(imc_counter->fd, PERF_EVENT_IOC_ENABLE, 0);
 }
 
-static void read_mem_bw_ioctl_perf_event_ioc_disable(int i)
+static void read_mem_bw_ioctl_perf_event_ioc_disable(struct imc_counter_config *imc_counter)
 {
-	ioctl(imc_counters_config[i].fd, PERF_EVENT_IOC_DISABLE, 0);
+	ioctl(imc_counter->fd, PERF_EVENT_IOC_DISABLE, 0);
 }
 
 /*
  * get_read_event_and_umask:	Parse config into event and umask
  * @cas_count_cfg:	Config
- * @count:		iMC number
+ * @imc_counter:	iMC counter config
  */
-static void get_read_event_and_umask(char *cas_count_cfg, unsigned int count)
+static void get_read_event_and_umask(char *cas_count_cfg, struct imc_counter_config *imc_counter)
 {
 	char *token[MAX_TOKENS];
 	int i = 0;
@@ -89,21 +89,21 @@ static void get_read_event_and_umask(char *cas_count_cfg, unsigned int count)
 		if (!token[i])
 			break;
 		if (strcmp(token[i], "event") == 0)
-			imc_counters_config[count].event = strtol(token[i + 1], NULL, 16);
+			imc_counter->event = strtol(token[i + 1], NULL, 16);
 		if (strcmp(token[i], "umask") == 0)
-			imc_counters_config[count].umask = strtol(token[i + 1], NULL, 16);
+			imc_counter->umask = strtol(token[i + 1], NULL, 16);
 	}
 }
 
-static int open_perf_read_event(int i, int cpu_no)
+static int open_perf_read_event(int cpu_no, struct imc_counter_config *imc_counter)
 {
-	imc_counters_config[i].fd =
-		perf_event_open(&imc_counters_config[i].pe, -1, cpu_no, -1,
+	imc_counter->fd =
+		perf_event_open(&imc_counter->pe, -1, cpu_no, -1,
 				PERF_FLAG_FD_CLOEXEC);
 
-	if (imc_counters_config[i].fd == -1) {
+	if (imc_counter->fd == -1) {
 		fprintf(stderr, "Error opening leader %llx\n",
-			imc_counters_config[i].pe.config);
+			imc_counter->pe.config);
 
 		return -1;
 	}
@@ -177,7 +177,7 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 		}
 
 		imc_counters_config[*count].type = type;
-		get_read_event_and_umask(cas_count_cfg, *count);
+		get_read_event_and_umask(cas_count_cfg, &imc_counters_config[*count]);
 		/* Do not fail after incrementing *count. */
 		*count += 1;
 		list_add(&imc_counter->entry, &imc_counters_list);
@@ -311,7 +311,7 @@ int initialize_read_mem_bw_imc(void)
 
 	/* Initialize perf_event_attr structures for all iMC's */
 	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_initialize_perf_event_attr(imc);
+		read_mem_bw_initialize_perf_event_attr(&imc_counters_config[imc]);
 
 	return 0;
 }
@@ -350,7 +350,7 @@ static int perf_open_imc_read_mem_bw(int cpu_no)
 		imc_counters_config[imc].fd = -1;
 
 	for (imc = 0; imc < imcs; imc++) {
-		ret = open_perf_read_event(imc, cpu_no);
+		ret = open_perf_read_event(cpu_no, &imc_counters_config[imc]);
 		if (ret)
 			goto close_fds;
 	}
@@ -373,13 +373,13 @@ static void do_imc_read_mem_bw_test(void)
 	int imc;
 
 	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_ioctl_perf_event_ioc_reset_enable(imc);
+		read_mem_bw_ioctl_perf_event_ioc_reset_enable(&imc_counters_config[imc]);
 
 	sleep(1);
 
 	/* Stop counters after a second to get results. */
 	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_ioctl_perf_event_ioc_disable(imc);
+		read_mem_bw_ioctl_perf_event_ioc_disable(&imc_counters_config[imc]);
 }
 
 /*
-- 
2.34.1

Re: [PATCH v3 2/3] selftests/resctrl: Replace counter index references with pointers

[Reinette Chatre]

Hi Yifan,

Thank you. I just have a few style fixup comments ...

On 5/22/26 2:05 AM, Yifan Wu wrote:
> Replace direct counter number references with pointers to remove the
> dependency on fixed array indexing and enable the use of different
> data structures for counter management.
> 
> Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
> ---
>  tools/testing/selftests/resctrl/resctrl_val.c | 62 +++++++++----------
>  1 file changed, 31 insertions(+), 31 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index a72dc4ae61fe..3d2b6919717a 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -42,40 +42,40 @@ static struct imc_counter_config imc_counters_config[MAX_IMCS];
>  LIST_HEAD(imc_counters_list);
>  static const struct resctrl_test *current_test;
>  
> -static void read_mem_bw_initialize_perf_event_attr(int i)
> +static void read_mem_bw_initialize_perf_event_attr(struct imc_counter_config *imc_counter)
>  {
> -	memset(&imc_counters_config[i].pe, 0,
> +	memset(&imc_counter->pe, 0,
>  	       sizeof(struct perf_event_attr));

nit: above can fit on a single line

> -	imc_counters_config[i].pe.type = imc_counters_config[i].type;
> -	imc_counters_config[i].pe.size = sizeof(struct perf_event_attr);
> -	imc_counters_config[i].pe.disabled = 1;
> -	imc_counters_config[i].pe.inherit = 1;
> -	imc_counters_config[i].pe.exclude_guest = 0;
> -	imc_counters_config[i].pe.config =
> -		imc_counters_config[i].umask << 8 |
> -		imc_counters_config[i].event;
> -	imc_counters_config[i].pe.sample_type = PERF_SAMPLE_IDENTIFIER;
> -	imc_counters_config[i].pe.read_format =
> +	imc_counter->pe.type = imc_counter->type;
> +	imc_counter->pe.size = sizeof(struct perf_event_attr);
> +	imc_counter->pe.disabled = 1;
> +	imc_counter->pe.inherit = 1;
> +	imc_counter->pe.exclude_guest = 0;
> +	imc_counter->pe.config =
> +		imc_counter->umask << 8 |
> +		imc_counter->event;

nit: above can fit on a single line

> +	imc_counter->pe.sample_type = PERF_SAMPLE_IDENTIFIER;
> +	imc_counter->pe.read_format =
>  		PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING;
>  }
>  

...

> @@ -89,21 +89,21 @@ static void get_read_event_and_umask(char *cas_count_cfg, unsigned int count)
>  		if (!token[i])
>  			break;
>  		if (strcmp(token[i], "event") == 0)
> -			imc_counters_config[count].event = strtol(token[i + 1], NULL, 16);
> +			imc_counter->event = strtol(token[i + 1], NULL, 16);
>  		if (strcmp(token[i], "umask") == 0)
> -			imc_counters_config[count].umask = strtol(token[i + 1], NULL, 16);
> +			imc_counter->umask = strtol(token[i + 1], NULL, 16);
>  	}
>  }
>  
> -static int open_perf_read_event(int i, int cpu_no)
> +static int open_perf_read_event(int cpu_no, struct imc_counter_config *imc_counter)
>  {
> -	imc_counters_config[i].fd =
> -		perf_event_open(&imc_counters_config[i].pe, -1, cpu_no, -1,
> +	imc_counter->fd =
> +		perf_event_open(&imc_counter->pe, -1, cpu_no, -1,
>  				PERF_FLAG_FD_CLOEXEC);

Please improve readibility here by moving the above two lines up while ensuring alignment with
open parenthesis. Specifically:
	imc_counter->fd = perf_event_open(&imc_counter->pe, -1, cpu_no, -1,
					  PERF_FLAG_FD_CLOEXEC);
...

With the style fixups:
| Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reinette

Re: [PATCH v3 2/3] selftests/resctrl: Replace counter index references with pointers

[wuyifan]

Hi Reinette,

Thanks for the review.

On 6/26/2026 6:14 AM, Reinette Chatre wrote:
> On 5/22/26 2:05 AM, Yifan Wu wrote:
>> Replace direct counter number references with pointers to remove the
>> dependency on fixed array indexing and enable the use of different
>> data structures for counter management.
>>
>> Signed-off-by: Yifan Wu<wuyifan50@huawei.com>
>> ---
> Please improve readibility here by moving the above two lines up while ensuring alignment with
> open parenthesis. Specifically:
> 	imc_counter->fd = perf_event_open(&imc_counter->pe, -1, cpu_no, -1,
> 					  PERF_FLAG_FD_CLOEXEC);
> ...
>
> With the style fixups:
> | Reviewed-by: Reinette Chatre<reinette.chatre@intel.com>
>
> Reinette

I will fix that.

Thanks,
Yifan

[PATCH v3 3/3] selftests/resctrl: Enable dynamic management of IMC counters via linked list

[Yifan Wu]

Remove the static array and the count and upper limit checks during
initialization, allowing the system to dynamically use all available
IMC counters detected by hardware.

Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
---
 tools/testing/selftests/resctrl/resctrl_val.c | 85 +++++++++----------
 1 file changed, 38 insertions(+), 47 deletions(-)

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index 3d2b6919717a..129e8d76222a 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -14,7 +14,6 @@
 #define READ_FILE_NAME		"cas_count_read"
 #define DYN_PMU_PATH		"/sys/bus/event_source/devices"
 #define SCALE			0.00006103515625
-#define MAX_IMCS		40
 #define MAX_TOKENS		5
 
 #define CON_MBM_LOCAL_BYTES_PATH		\
@@ -37,8 +36,6 @@ struct imc_counter_config {
 };
 
 static char mbm_total_path[1024];
-static int imcs;
-static struct imc_counter_config imc_counters_config[MAX_IMCS];
 LIST_HEAD(imc_counters_list);
 static const struct resctrl_test *current_test;
 
@@ -111,12 +108,11 @@ static int open_perf_read_event(int cpu_no, struct imc_counter_config *imc_count
 	return 0;
 }
 
-static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
-				    unsigned int *count)
+static int parse_imc_read_bw_events(char *imc_dir, unsigned int type)
 {
 	char imc_events_dir[PATH_MAX], imc_counter_cfg[PATH_MAX];
 	struct imc_counter_config *imc_counter;
-	unsigned int orig_count = *count;
+	bool found_event = false;
 	char cas_count_cfg[1024];
 	struct dirent *ep;
 	int path_len;
@@ -166,23 +162,18 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 			ksft_perror("Could not get iMC cas count read");
 			goto out_close;
 		}
-		if (*count >= MAX_IMCS) {
-			ksft_print_msg("Maximum iMC count exceeded\n");
-			goto out_close;
-		}
 		imc_counter = calloc(1, sizeof(*imc_counter));
 		if (!imc_counter) {
 			ksft_perror("Unable to allocate memory for iMC counters");
 			goto out_close;
 		}
 
-		imc_counters_config[*count].type = type;
-		get_read_event_and_umask(cas_count_cfg, &imc_counters_config[*count]);
-		/* Do not fail after incrementing *count. */
-		*count += 1;
+		imc_counter->type = type;
+		get_read_event_and_umask(cas_count_cfg, imc_counter);
 		list_add(&imc_counter->entry, &imc_counters_list);
+		found_event = true;
 	}
-	if (*count == orig_count) {
+	if (!found_event) {
 		ksft_print_msg("Unable to find events in %s\n", imc_events_dir);
 		goto out_close;
 	}
@@ -197,7 +188,7 @@ static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
 }
 
 /* Get type and config of an iMC counter's read event. */
-static int read_from_imc_dir(char *imc_dir, unsigned int *count)
+static int read_from_imc_dir(char *imc_dir)
 {
 	char imc_counter_type[PATH_MAX];
 	unsigned int type;
@@ -225,7 +216,7 @@ static int read_from_imc_dir(char *imc_dir, unsigned int *count)
 		ksft_perror("Could not get iMC type");
 		return -1;
 	}
-	ret = parse_imc_read_bw_events(imc_dir, type, count);
+	ret = parse_imc_read_bw_events(imc_dir, type);
 	if (ret) {
 		ksft_print_msg("Unable to parse bandwidth event and umask\n");
 		return ret;
@@ -242,14 +233,13 @@ static int read_from_imc_dir(char *imc_dir, unsigned int *count)
  * counter's event and umask for the memory read events that will be
  * measured.
  *
- * Enumerate all these details into an array of structures.
+ * Enumerate all these details into a linked list of structures.
  *
  * Return: >= 0 on success. < 0 on failure.
  */
-static int num_of_imcs(void)
+static int enumerate_imcs(void)
 {
 	char imc_dir[512], *temp;
-	unsigned int count = 0;
 	struct dirent *ep;
 	int ret;
 	DIR *dp;
@@ -278,7 +268,7 @@ static int num_of_imcs(void)
 			if (temp[0] >= '0' && temp[0] <= '9') {
 				sprintf(imc_dir, "%s/%s/", DYN_PMU_PATH,
 					ep->d_name);
-				ret = read_from_imc_dir(imc_dir, &count);
+				ret = read_from_imc_dir(imc_dir);
 				if (ret) {
 					closedir(dp);
 
@@ -287,7 +277,7 @@ static int num_of_imcs(void)
 			}
 		}
 		closedir(dp);
-		if (count == 0) {
+		if (list_empty(&imc_counters_list)) {
 			ksft_print_msg("Unable to find iMC counters\n");
 
 			return -1;
@@ -298,20 +288,22 @@ static int num_of_imcs(void)
 		return -1;
 	}
 
-	return count;
+	return 0;
 }
 
 int initialize_read_mem_bw_imc(void)
 {
-	int imc;
+	struct imc_counter_config *imc_counter;
+	int ret;
 
-	imcs = num_of_imcs();
-	if (imcs <= 0)
-		return imcs;
+	ret = enumerate_imcs();
+	if (ret < 0)
+		return ret;
 
 	/* Initialize perf_event_attr structures for all iMC's */
-	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_initialize_perf_event_attr(&imc_counters_config[imc]);
+	list_for_each_entry(imc_counter, &imc_counters_list, entry) {
+		read_mem_bw_initialize_perf_event_attr(imc_counter);
+	}
 
 	return 0;
 }
@@ -328,11 +320,11 @@ void cleanup_read_mem_bw_imc(void)
 
 static void perf_close_imc_read_mem_bw(void)
 {
-	int mc;
+	struct imc_counter_config *imc_counter;
 
-	for (mc = 0; mc < imcs; mc++) {
-		if (imc_counters_config[mc].fd != -1)
-			close(imc_counters_config[mc].fd);
+	list_for_each_entry(imc_counter, &imc_counters_list, entry) {
+		if (imc_counter->fd != -1)
+			close(imc_counter->fd);
 	}
 }
 
@@ -344,13 +336,14 @@ static void perf_close_imc_read_mem_bw(void)
  */
 static int perf_open_imc_read_mem_bw(int cpu_no)
 {
-	int imc, ret;
+	struct imc_counter_config *imc_counter;
+	int ret;
 
-	for (imc = 0; imc < imcs; imc++)
-		imc_counters_config[imc].fd = -1;
+	list_for_each_entry(imc_counter, &imc_counters_list, entry)
+		imc_counter->fd = -1;
 
-	for (imc = 0; imc < imcs; imc++) {
-		ret = open_perf_read_event(cpu_no, &imc_counters_config[imc]);
+	list_for_each_entry(imc_counter, &imc_counters_list, entry) {
+		ret = open_perf_read_event(cpu_no, imc_counter);
 		if (ret)
 			goto close_fds;
 	}
@@ -370,16 +363,16 @@ static int perf_open_imc_read_mem_bw(int cpu_no)
  */
 static void do_imc_read_mem_bw_test(void)
 {
-	int imc;
+	struct imc_counter_config *imc_counter;
 
-	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_ioctl_perf_event_ioc_reset_enable(&imc_counters_config[imc]);
+	list_for_each_entry(imc_counter, &imc_counters_list, entry)
+		read_mem_bw_ioctl_perf_event_ioc_reset_enable(imc_counter);
 
 	sleep(1);
 
 	/* Stop counters after a second to get results. */
-	for (imc = 0; imc < imcs; imc++)
-		read_mem_bw_ioctl_perf_event_ioc_disable(&imc_counters_config[imc]);
+	list_for_each_entry(imc_counter, &imc_counters_list, entry)
+		read_mem_bw_ioctl_perf_event_ioc_disable(imc_counter);
 }
 
 /*
@@ -394,17 +387,15 @@ static void do_imc_read_mem_bw_test(void)
 static int get_read_mem_bw_imc(float *bw_imc)
 {
 	float reads = 0, of_mul_read = 1;
-	int imc;
+	struct imc_counter_config *r;
 
 	/*
 	 * Log read event values from all iMC counters into
 	 * struct imc_counter_config.
 	 * Take overflow into consideration before calculating total bandwidth.
 	 */
-	for (imc = 0; imc < imcs; imc++) {
+	list_for_each_entry(r, &imc_counters_list, entry) {
 		struct membw_read_format measurement;
-		struct imc_counter_config *r =
-			&imc_counters_config[imc];
 
 		if (read(r->fd, &measurement, sizeof(measurement)) == -1) {
 			ksft_perror("Couldn't get read bandwidth through iMC");
-- 
2.34.1

Re: [PATCH v3 3/3] selftests/resctrl: Enable dynamic management of IMC counters via linked list

[Reinette Chatre]

Hi Yifan,

On 5/22/26 2:05 AM, Yifan Wu wrote:
> @@ -242,14 +233,13 @@ static int read_from_imc_dir(char *imc_dir, unsigned int *count)
>   * counter's event and umask for the memory read events that will be
>   * measured.
>   *
> - * Enumerate all these details into an array of structures.
> + * Enumerate all these details into a linked list of structures.
>   *
>   * Return: >= 0 on success. < 0 on failure.
>   */
> -static int num_of_imcs(void)
> +static int enumerate_imcs(void)

The first sentence of this function's comments still describes the behavior being
changed in this patch. How about a fixup like below:

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index 129e8d76222a..fe3b3517ae49 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -226,12 +226,10 @@ static int read_from_imc_dir(char *imc_dir)
 }
 
 /*
- * A system can have 'n' number of iMC (Integrated Memory Controller)
- * counters, get that 'n'. Discover the properties of the available
- * counters in support of needed performance measurement via perf.
- * For each iMC counter get it's type and config. Also obtain each
- * counter's event and umask for the memory read events that will be
- * measured.
+ * Discover the properties of the available iMC (Integrated Memory Controller)
+ * counters in support of needed performance measurement via perf. For each iMC
+ * counter get it's type and config. Also obtain each counter's event and umask
+ * for the memory read events that will be measured.
  *
  * Enumerate all these details into a linked list of structures.
  *

...  
>  int initialize_read_mem_bw_imc(void)
>  {
> -	int imc;
> +	struct imc_counter_config *imc_counter;
> +	int ret;
>  
> -	imcs = num_of_imcs();
> -	if (imcs <= 0)
> -		return imcs;
> +	ret = enumerate_imcs();
> +	if (ret < 0)
> +		return ret;
>  
>  	/* Initialize perf_event_attr structures for all iMC's */
> -	for (imc = 0; imc < imcs; imc++)
> -		read_mem_bw_initialize_perf_event_attr(&imc_counters_config[imc]);
> +	list_for_each_entry(imc_counter, &imc_counters_list, entry) {
> +		read_mem_bw_initialize_perf_event_attr(imc_counter);
> +	}

nit: unnecessary braces

>  
>  	return 0;
>  }
> @@ -328,11 +320,11 @@ void cleanup_read_mem_bw_imc(void)
>  
>  static void perf_close_imc_read_mem_bw(void)
>  {
> -	int mc;
> +	struct imc_counter_config *imc_counter;
>  
> -	for (mc = 0; mc < imcs; mc++) {
> -		if (imc_counters_config[mc].fd != -1)
> -			close(imc_counters_config[mc].fd);
> +	list_for_each_entry(imc_counter, &imc_counters_list, entry) {
> +		if (imc_counter->fd != -1)
> +			close(imc_counter->fd);
>  	}
>  }
>  
With fixup applied and nit addressed:
| Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reinette

Re: [PATCH v3 3/3] selftests/resctrl: Enable dynamic management of IMC counters via linked list

[wuyifan]

Hi Reinette,

On 6/26/2026 6:14 AM, Reinette Chatre wrote:
> With fixup applied and nit addressed:
> | Reviewed-by: Reinette Chatre<reinette.chatre@intel.com>
>
> Reinette
Thanks for the review. I will fix that.

Thanks,
Yifan