From e8eb9afd4c53e67d834f520a42a641adb874a463 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Wed, 8 Mar 2017 13:09:00 +0000
Subject: igt: Exercise the shrinker

Introduce a new fork helper that spawns a process that just repeatedly
calls i915_gem_shrink_all() and watch what happens as we try to use
objects that have been shrunk.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 lib/igt_aux.c     | 39 +++++++++++++++++++++++++++++++++++++++
 lib/igt_aux.h     |  3 +++
 lib/igt_debugfs.c | 22 ++++++++++++++++++++++
 lib/igt_debugfs.h |  9 +++++++++
 4 files changed, 73 insertions(+)

(limited to 'lib')

diff --git a/lib/igt_aux.c b/lib/igt_aux.c
index 5117dbec..7ee279a3 100644
--- a/lib/igt_aux.c
+++ b/lib/igt_aux.c
@@ -349,6 +349,45 @@ void igt_stop_signal_helper(void)
 	sig_stat = 0;
 }
 
+static struct igt_helper_process shrink_helper;
+static void __attribute__((noreturn)) shrink_helper_process(pid_t pid)
+{
+	while (1) {
+		igt_drop_caches_set(DROP_SHRINK_ALL);
+		usleep(1000 * 1000 / 50);
+		if (kill(pid, 0)) /* Parent has died, so must we. */
+			exit(0);
+	}
+}
+
+/**
+ * igt_fork_shrink_helper:
+ *
+ * Fork a child process using #igt_fork_helper to force all available objects
+ * to be paged out (via i915_gem_shrink()).
+ *
+ * This is useful to exercise swapping paths, without requiring us to hit swap.
+ *
+ * This should only be used from an igt_fixture.
+ */
+void igt_fork_shrink_helper(void)
+{
+	assert(!igt_only_list_subtests());
+	igt_require(igt_drop_caches_has(DROP_SHRINK_ALL));
+	igt_fork_helper(&shrink_helper)
+		shrink_helper_process(getppid());
+}
+
+/**
+ * igt_stop_shrink_helper:
+ *
+ * Stops the child process spawned with igt_fork_shrink_helper().
+ */
+void igt_stop_shrink_helper(void)
+{
+	igt_stop_helper(&shrink_helper);
+}
+
 #if HAVE_UDEV
 #include <libudev.h>
 
diff --git a/lib/igt_aux.h b/lib/igt_aux.h
index cb54ca5e..13f6f156 100644
--- a/lib/igt_aux.h
+++ b/lib/igt_aux.h
@@ -51,6 +51,9 @@ extern int num_trash_bos;
 void igt_fork_signal_helper(void);
 void igt_stop_signal_helper(void);
 
+void igt_fork_shrink_helper(void);
+void igt_stop_shrink_helper(void);
+
 void igt_fork_hang_detector(int fd);
 void igt_stop_hang_detector(void);
 
diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index e64d001b..0a991a1f 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -872,6 +872,28 @@ void igt_pipe_crc_collect_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc)
  * Drop caches
  */
 
+/**
+ * igt_drop_caches_has:
+ * @val: bitmask for DROP_* values
+ *
+ * This queries the debugfs to see if it supports the full set of desired
+ * operations.
+ */
+bool igt_drop_caches_has(uint64_t val)
+{
+	FILE *file;
+	uint64_t mask;
+
+	mask = 0;
+	file = igt_debugfs_fopen("i915_gem_drop_caches", "r");
+	if (file) {
+		fscanf(file, "0x%" PRIx64, &mask);
+		fclose(file);
+	}
+
+	return (val & mask) == val;
+}
+
 /**
  * igt_drop_caches_set:
  * @val: bitmask for DROP_* values
diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
index 5587ad40..aa59f8a8 100644
--- a/lib/igt_debugfs.h
+++ b/lib/igt_debugfs.h
@@ -169,6 +169,13 @@ void igt_require_hpd_storm_ctl(void);
  * Also drop freed objects.
  */
 #define DROP_FREED 0x10
+/**
+ * DROP_SHRINK_ALL:
+ *
+ * Force all unpinned buffers to be evicted from their GTT and returned to the
+ * system.
+ */
+#define DROP_SHRINK_ALL 0x20
 /**
  * DROP_ALL:
  *
@@ -176,10 +183,12 @@ void igt_require_hpd_storm_ctl(void);
  */
 #define DROP_ALL (DROP_UNBOUND | \
 		  DROP_BOUND | \
+		  DROP_SHRINK_ALL | \
 		  DROP_RETIRE | \
 		  DROP_ACTIVE | \
 		  DROP_FREED)
 
+bool igt_drop_caches_has(uint64_t val);
 void igt_drop_caches_set(uint64_t val);
 
 /*
-- 
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