[PATCH] dma-buf/sync-file: Defer creation of sync_file->name

[Chris Wilson]

Constructing the name takes the majority of the time for allocating a
sync_file to wrap a fence, and the name is very rarely used (only via
the sync_file status user interface). To reduce the impact on the common
path (that of creating sync_file to pass around), defer the construction
of the name until it is first used.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: Gustavo Padovan <gustavo at padovan.org>
---
 drivers/dma-buf/sync_file.c | 18 +++++++++++-------
 include/linux/sync_file.h   |  2 +-
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 2321035f6204..2cccfa834778 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -82,11 +82,6 @@ struct sync_file *sync_file_create(struct dma_fence *fence)
 
 	sync_file->fence = dma_fence_get(fence);
 
-	snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%llu-%d",
-		 fence->ops->get_driver_name(fence),
-		 fence->ops->get_timeline_name(fence), fence->context,
-		 fence->seqno);
-
 	return sync_file;
 }
 EXPORT_SYMBOL(sync_file_create);
@@ -268,7 +263,7 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 		goto err;
 	}
 
-	strlcpy(sync_file->name, name, sizeof(sync_file->name));
+	strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name));
 	return sync_file;
 
 err:
@@ -422,7 +417,16 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 	}
 
 no_fences:
-	strlcpy(info.name, sync_file->name, sizeof(info.name));
+	if (!sync_file->user_name[0]) {
+		scnprintf(sync_file->user_name,
+			  sizeof(sync_file->user_name),
+			  "%s-%s%llu-%d",
+			  sync_file->fence->ops->get_driver_name(sync_file->fence),
+			  sync_file->fence->ops->get_timeline_name(sync_file->fence),
+			  sync_file->fence->context,
+			  sync_file->fence->seqno);
+	}
+	strlcpy(info.name, sync_file->user_name, sizeof(info.name));
 	info.status = dma_fence_is_signaled(sync_file->fence);
 	info.num_fences = num_fences;
 
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index 3e3ab84fc4cd..0cbeff29f510 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -34,7 +34,7 @@
 struct sync_file {
 	struct file		*file;
 	struct kref		kref;
-	char			name[32];
+	char			user_name[32];
 #ifdef CONFIG_DEBUG_FS
 	struct list_head	sync_file_list;
 #endif
-- 
2.11.0