selftests/resctrl: Only support measured read operation

The CMT, MBM, and MBA tests rely on a benchmark to generate
memory traffic. By default this is the "fill_buf" benchmark that
can be replaced via the "-b" command line argument.

The original intent of the "-b" command line parameter was
to replace the default "fill_buf" benchmark, but the implementation
also exposes an alternative use case where the "fill_buf" parameters
itself can be modified. One of the parameters to "fill_buf" is the
"operation" that can be either "read" or "write" and indicates
whether the "fill_buf" should use "read" or "write" operations on the
allocated buffer.

While replacing "fill_buf" default parameters is technically possible,
replacing the default "read" parameter with "write" is not supported
because the MBA and MBM tests only measure "read" operations. The
"read" operation is also most appropriate for the CMT test that aims
to use the benchmark to allocate into the cache.

Avoid any potential inconsistencies between test and measurement by
removing code for unsupported "write" operations to the buffer.
Ignore any attempt from user space to enable this unsupported test
configuration, instead always use read operations.

Keep the initialization of the, now unused, "fill_buf" parameters
to reserve these parameter positions since it has been exposed as an API.
Future parameter additions cannot use these parameter positions.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
index 854f0108d8e62c6a25b900445b03a57e09cdc4a5..e4f1cea317f12a30229d52ac5492ddeff8277fba 100644 (file)
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/tools/testing/selftests/resctrl/fill_buf.c
@@ -88,18 +88,6 @@ static int fill_one_span_read(unsigned char *buf, size_t buf_size)
        return sum;
 }
 
-static void fill_one_span_write(unsigned char *buf, size_t buf_size)
-{
-       unsigned char *end_ptr = buf + buf_size;
-       unsigned char *p;
-
-       p = buf;
-       while (p < end_ptr) {
-               *p = '1';
-               p += (CL_SIZE / 2);
-       }
-}
-
 void fill_cache_read(unsigned char *buf, size_t buf_size, bool once)
 {
        int ret = 0;
@@ -114,15 +102,6 @@ void fill_cache_read(unsigned char *buf, size_t buf_size, bool once)
        *value_sink = ret;
 }
 
-static void fill_cache_write(unsigned char *buf, size_t buf_size, bool once)
-{
-       while (1) {
-               fill_one_span_write(buf, buf_size);
-               if (once)
-                       break;
-       }
-}
-
 unsigned char *alloc_buffer(size_t buf_size, int memflush)
 {
        void *buf = NULL;
@@ -151,7 +130,7 @@ unsigned char *alloc_buffer(size_t buf_size, int memflush)
        return buf;
 }
 
-int run_fill_buf(size_t buf_size, int memflush, int op)
+int run_fill_buf(size_t buf_size, int memflush)
 {
        unsigned char *buf;
 
@@ -159,10 +138,7 @@ int run_fill_buf(size_t buf_size, int memflush, int op)
        if (!buf)
                return -1;
 
-       if (op == 0)
-               fill_cache_read(buf, buf_size, false);
-       else
-               fill_cache_write(buf, buf_size, false);
+       fill_cache_read(buf, buf_size, false);
 
        free(buf);
 

diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 51f5f4b25e0662285ce7536c875475d5e7d18d7a..ba1ce1b356992219b78b3c892d3e260d1c881881 100644 (file)
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -142,7 +142,7 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu,
 unsigned char *alloc_buffer(size_t buf_size, int memflush);
 void mem_flush(unsigned char *buf, size_t buf_size);
 void fill_cache_read(unsigned char *buf, size_t buf_size, bool once);
-int run_fill_buf(size_t buf_size, int memflush, int op);
+int run_fill_buf(size_t buf_size, int memflush);
 int initialize_mem_bw_imc(void);
 int measure_mem_bw(const struct user_params *uparams,
                   struct resctrl_val_param *param, pid_t bm_pid,

diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index e7878077883f0bebb7511e00a7473de3d71d79a6..0f91c475b255a87e5cea30e01ee8b5a812a65094 100644 (file)
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -265,13 +265,16 @@ last_arg:
                        ksft_exit_fail_msg("Out of memory!\n");
                uparams.benchmark_cmd[1] = span_str;
                uparams.benchmark_cmd[2] = "1";
-               uparams.benchmark_cmd[3] = "0";
                /*
+                * Third parameter was previously used for "operation"
+                * (read/write) of which only (now default) "read"/"0"
+                * works.
                 * Fourth parameter was previously used to indicate
                 * how long "fill_buf" should run for, with "false"
                 * ("fill_buf" will keep running until terminated)
                 * the only option that works.
                 */
+               uparams.benchmark_cmd[3] = NULL;
                uparams.benchmark_cmd[4] = NULL;
        }
 

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index b0f3c594c4da4721ee63772aee38c9f21d51337a..113ca18d67c1620f09d3b03a304b1d42c6fcf4fb 100644 (file)
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -622,8 +622,8 @@ close_fp:
  */
 static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
 {
-       int operation, ret, memflush;
        char **benchmark_cmd;
+       int ret, memflush;
        size_t span;
        FILE *fp;
 
@@ -643,9 +643,8 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
                /* Execute default fill_buf benchmark */
                span = strtoul(benchmark_cmd[1], NULL, 10);
                memflush =  atoi(benchmark_cmd[2]);
-               operation = atoi(benchmark_cmd[3]);
 
-               if (run_fill_buf(span, memflush, operation))
+               if (run_fill_buf(span, memflush))
                        fprintf(stderr, "Error in running fill buffer\n");
        } else {
                /* Execute specified benchmark */