[PATCH i-g-t 2/2] tests/gem_exec_await: Add a memory pressure subtest

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Memory pressure subtest attempts to provoke system overload which can
cause GPU hangs, especially when combined with spin batches which do
not allow for some nop instructions to provide relief.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 tests/i915/gem_exec_await.c | 107 ++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)

diff --git a/tests/i915/gem_exec_await.c b/tests/i915/gem_exec_await.c
index 3ea5b5903c6b..ccb5159a6fe1 100644
--- a/tests/i915/gem_exec_await.c
+++ b/tests/i915/gem_exec_await.c
@@ -30,6 +30,11 @@
 
 #include <sys/ioctl.h>
 #include <sys/signal.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <sched.h>
 
 #define LOCAL_I915_EXEC_NO_RELOC (1<<11)
 #define LOCAL_I915_EXEC_HANDLE_LUT (1<<12)
@@ -227,6 +232,92 @@ static void wide(int fd, int ring_size, int timeout, unsigned int flags)
 	free(exec);
 }
 
+struct thread {
+	pthread_t thread;
+	volatile bool done;
+};
+
+static unsigned long get_meminfo(const char *info, const char *tag)
+{
+        const char *str;
+        unsigned long val;
+
+        str = strstr(info, tag);
+        if (str && sscanf(str + strlen(tag), " %lu", &val) == 1)
+                return val >> 10;
+
+        igt_warn("Unrecognised /proc/meminfo field: '%s'\n", tag);
+        return 0;
+}
+
+static unsigned long get_avail_ram_mb(void)
+{
+	int fd;
+	int ret;
+	char buf[4096];
+	unsigned long ram;
+
+	fd = open("/proc/meminfo", O_RDONLY);
+	igt_assert_fd(fd);
+
+	ret = read(fd, buf, sizeof(buf));
+	igt_assert(ret >= 0);
+
+	close(fd);
+
+	ram = get_meminfo(buf, "MemAvailable:");
+	ram += get_meminfo(buf, "Buffers:");
+	ram += get_meminfo(buf, "Cached:");
+	ram += get_meminfo(buf, "SwapCached:");
+
+	return ram;
+}
+
+#define PAGE_SIZE 4096
+static void *mempressure(void *arg)
+{
+	struct thread *thread = arg;
+	const unsigned int sz_mb = 2;
+	const unsigned int sz = sz_mb << 20;
+	unsigned int n = 0, max = 0;
+	unsigned int blocks;
+	void **ptr = NULL;
+
+	while (!thread->done) {
+		unsigned long ram_mb = get_avail_ram_mb();
+
+		if (!ptr) {
+			blocks = ram_mb / sz_mb;
+			ptr = calloc(blocks, sizeof(void *));
+			igt_assert(ptr);
+		} else if (ram_mb < 384) {
+			blocks = max + 1;
+		}
+
+		if (ptr[n])
+			munmap(ptr[n], sz);
+
+		ptr[n] = mmap(NULL, sz, PROT_WRITE,
+			      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+		assert(ptr[n] != MAP_FAILED);
+
+		madvise(ptr[n], sz, MADV_HUGEPAGE);
+
+		for (size_t page = 0; page < sz; page += PAGE_SIZE)
+			*(volatile uint32_t *)((unsigned char *)ptr[n] + page) =
+				0;
+
+		if (n > max)
+			max = n;
+
+		n++;
+
+		if (n >= blocks)
+			n = 0;
+	}
+
+	return NULL;
+}
 igt_main
 {
 	int ring_size = 0;
@@ -255,6 +346,22 @@ igt_main
 		wide(device, ring_size, 20, CONTEXTS);
 	}
 
+	igt_subtest("wide-contexts-mempressure") {
+		struct thread thread = { };
+		int ret;
+
+		gem_require_contexts(device);
+
+		ret = pthread_create(&thread.thread, NULL, mempressure,
+				     &thread);
+		igt_assert_eq(ret, 0);
+
+		wide(device, ring_size, 20, CONTEXTS);
+
+		thread.done = true;
+		pthread_join(thread.thread, NULL);
+	}
+
 	igt_fixture {
 		igt_stop_hang_detector();
 		close(device);
-- 
2.19.1

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