[PATCH v2] fs: improve ramfs_truncate speed

Marcin Niestroj m.niestroj at grinn-global.com
Wed Sep 26 04:08:46 PDT 2018


During sequential writes into single file, fs layer is consequently
calling ramfs_truncate() function. When file size grows
ramfs_truncate() takes more and more time to complete, due to
interations through all already written data chunks. As an example
loading ~450M image using usb fastboot protocol took over 500s to
complete.

Use ramfs_find_chunk() function to search for last chunk of data in
ramfs_truncate() implementation, which saves a lot of loop
iterations. As a result loading ~450M image using usb fastboot
protocol takes around 25s now.

Tested-by: Maciej Zagrabski <m.zagrabski at grinn-global.com>
Signed-off-by: Marcin Niestroj <m.niestroj at grinn-global.com>
---
Changes v1 -> v2 (suggested by Sascha):
 * use positive logic, i.e. 'if (data)'
 * rebase patch on top of "fs: ramfs: make chunk counting in 
   truncate() better readable"

 fs/ramfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ramfs.c b/fs/ramfs.c
index 8ba8d77de..e3f83bca3 100644
--- a/fs/ramfs.c
+++ b/fs/ramfs.c
@@ -379,7 +379,9 @@ static int ramfs_truncate(struct device_d *dev, FILE *f, ulong size)
 	}
 
 	if (newchunks > oldchunks) {
-		if (!data) {
+		if (data) {
+			data = ramfs_find_chunk(node, oldchunks);
+		} else {
 			node->data = ramfs_get_chunk();
 			if (!node->data)
 				return -ENOMEM;
-- 
2.19.0




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