[igt-dev] [PATCH i-g-t] lib: Incrementally mlock()

[Chris Wilson]

As we already have the previous portion of the mmap mlocked, we only
need to mlock() the fresh portion for testing available memory.

v2: Fixup the uint64_t pointer arithmetric and only use a single mmap to
avoid subsequent mlock fail (for reasons unknown, but bet on mm/).

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Caz Yokoyama <Caz.Yokoyama at intel.com>
---
 lib/igt_aux.h             |  2 +-
 lib/intel_os.c            | 40 +++++++++++++++++++++------------------
 tests/eviction_common.c   | 17 +++++++++--------
 tests/i915/i915_suspend.c | 17 +++--------------
 4 files changed, 35 insertions(+), 41 deletions(-)

diff --git a/lib/igt_aux.h b/lib/igt_aux.h
index fb02c026a..09b6246bf 100644
--- a/lib/igt_aux.h
+++ b/lib/igt_aux.h
@@ -194,7 +194,7 @@ void intel_purge_vm_caches(int fd);
 uint64_t intel_get_avail_ram_mb(void);
 uint64_t intel_get_total_ram_mb(void);
 uint64_t intel_get_total_swap_mb(void);
-size_t intel_get_total_pinnable_mem(void);
+void *intel_get_total_pinnable_mem(size_t *pinned);
 
 int __intel_check_memory(uint64_t count, uint64_t size, unsigned mode,
 			 uint64_t *out_required, uint64_t *out_total);
diff --git a/lib/intel_os.c b/lib/intel_os.c
index e1e31e230..dd93bea1a 100644
--- a/lib/intel_os.c
+++ b/lib/intel_os.c
@@ -227,11 +227,9 @@ intel_get_total_swap_mb(void)
  *
  * Returns: Amount of memory that can be safely pinned, in bytes.
  */
-size_t
-intel_get_total_pinnable_mem(void)
+void *intel_get_total_pinnable_mem(size_t *total)
 {
 	uint64_t *can_mlock, pin, avail;
-	size_t ret;
 
 	pin = (intel_get_total_ram_mb() + 1) << 20;
 	avail = (intel_get_avail_ram_mb() + 1) << 20;
@@ -245,34 +243,40 @@ intel_get_total_pinnable_mem(void)
 	 */
 	*can_mlock = (avail >> 1) + (avail >> 2);
 	if (mlock(can_mlock, *can_mlock)) {
-		*can_mlock = 0;
-		goto out;
+		munmap(can_mlock, pin);
+		return MAP_FAILED;
 	}
 
 	for (uint64_t inc = 1024 << 20; inc >= 4 << 10; inc >>= 2) {
-		igt_debug("Testing mlock %'"PRIu64" B (%'"PRIu64" MiB)\n",
-			  *can_mlock, *can_mlock >> 20);
+		uint64_t locked = *can_mlock;
+
+		igt_debug("Testing mlock %'"PRIu64"B (%'"PRIu64"MiB) + %'"PRIu64"B\n",
+			  locked, locked >> 20, inc);
 
 		igt_fork(child, 1) {
-			for (uint64_t bytes = *can_mlock;
-			     bytes <= pin;
-			     bytes += inc) {
-				if (mlock(can_mlock, bytes))
+			uint64_t bytes = *can_mlock;
+
+			while (bytes <= pin) {
+				if (mlock((void *)can_mlock + bytes, inc))
 					break;
 
-				*can_mlock = bytes;
+				*can_mlock = bytes += inc;
 				__sync_synchronize();
 			}
 		}
 		__igt_waitchildren();
-		igt_assert(!mlock(can_mlock, *can_mlock));
-	}
 
-out:
-	ret = *can_mlock;
-	munmap(can_mlock, pin);
+		if (*can_mlock > locked + inc) { /* Weird bit of mm/ lore */
+			*can_mlock -= inc;
+			igt_debug("Claiming mlock %'"PRIu64"B (%'"PRIu64"MiB)\n",
+				  *can_mlock, *can_mlock >> 20);
+			igt_assert(!mlock((void *)can_mlock + locked,
+					  *can_mlock - locked));
+		}
+	}
 
-	return ret;
+	*total = pin;
+	return can_mlock;
 }
 
 static uint64_t vfs_file_max(void)
diff --git a/tests/eviction_common.c b/tests/eviction_common.c
index 321772ba7..a3b9e4167 100644
--- a/tests/eviction_common.c
+++ b/tests/eviction_common.c
@@ -133,23 +133,24 @@ static void mlocked_evictions(int fd, struct igt_eviction_test_ops *ops,
 			      uint64_t surface_size,
 			      uint64_t surface_count)
 {
+	uint64_t sz, pin, total;
 	void *mem;
-	uint64_t sz, pin_total;
 
 	intel_require_memory(surface_count, surface_size, CHECK_RAM);
 
-	sz = surface_size*surface_count;
-	pin_total = intel_get_total_pinnable_mem();
-	igt_require(pin_total > sz);
-
-	mem = mmap(NULL, pin_total, PROT_READ, MAP_SHARED | MAP_ANON, -1, 0);
+	mem = intel_get_total_pinnable_mem(&total);
 	igt_assert(mem != MAP_FAILED);
+	pin = *(uint64_t *)mem;
+	igt_assert(!munlock(mem, pin));
+
+	sz = surface_size * surface_count;
+	igt_require(pin > sz);
 
 	igt_fork(child, 1) {
 		uint32_t *bo;
 		uint64_t n;
 		int ret;
-		size_t lock = pin_total - sz;
+		size_t lock = pin - sz;
 
 		bo = malloc(surface_count * sizeof(*bo));
 		igt_assert(bo);
@@ -186,7 +187,7 @@ static void mlocked_evictions(int fd, struct igt_eviction_test_ops *ops,
 	}
 	igt_waitchildren();
 
-	munmap(mem, pin_total);
+	munmap(mem, total);
 }
 
 static int swapping_evictions(int fd, struct igt_eviction_test_ops *ops,
diff --git a/tests/i915/i915_suspend.c b/tests/i915/i915_suspend.c
index 84cb3b490..cd7cf9675 100644
--- a/tests/i915/i915_suspend.c
+++ b/tests/i915/i915_suspend.c
@@ -163,25 +163,14 @@ test_sysfs_reader(bool hibernate)
 static void
 test_shrink(int fd, unsigned int mode)
 {
-	void *mem;
 	size_t size;
+	void *mem;
 
 	gem_quiescent_gpu(fd);
 	intel_purge_vm_caches(fd);
 
-	size = intel_get_total_pinnable_mem();
-	igt_require(size > 64 << 20);
-	size -= 64 << 20;
-
-	mem = mmap(NULL, size, PROT_READ, MAP_SHARED | MAP_ANON, -1, 0);
-
-	intel_purge_vm_caches(fd);
-
-	igt_debug("Locking %'zu B (%'zu MiB)\n",
-		  size, size >> 20);
-	igt_assert(!mlock(mem, size));
-	igt_info("Locked %'zu B (%'zu MiB)\n",
-		 size, size >> 20);
+	mem = intel_get_total_pinnable_mem(&size);
+	igt_assert(mem != MAP_FAILED);
 
 	intel_purge_vm_caches(fd);
 	igt_system_suspend_autoresume(mode, SUSPEND_TEST_NONE);
-- 
2.20.1