[PATCH] copy_chunk buffer size

[Ralph Böhme]

Hi!

Attached is a patch that changes copy_chunk to use a larger, talloced
buffer instead of a fixed size, small 64 KB buffer.

Please review&push if ok. Thanks!

-Ralph

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From 5d9b4e29f3884a8032dc61e9685f6c59af22313d Mon Sep 17 00:00:00 2001
From: Ralph Boehme <slow at samba.org>
Date: Wed, 1 Jul 2015 17:57:36 +0200
Subject: [PATCH] s3:vfs: copy_chunk buffer size

Use a dynamically allocated copy_chunk buffer size with an upper bound
of 8 MB for now.

The previous size of 64 KB has proven to really hurt performance,
especially with "strict locking = yes".

The SMB2 protocol level maximum allowed copy_chunk size is 1 MB, that's
what will be used as buffer size in the typical case.

With the AAPL copyfile extension the requested copy_chunk size is the
size whole file, which would then make use of a larger buffer up to the
limit of 8 MB.

Signed-off-by: Ralph Boehme <slow at samba.org>
---
 source3/modules/vfs_default.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/source3/modules/vfs_default.c b/source3/modules/vfs_default.c
index 9b434a0..6982634 100644
--- a/source3/modules/vfs_default.c
+++ b/source3/modules/vfs_default.c
@@ -1395,7 +1395,7 @@ static NTSTATUS vfswrap_fsctl(struct vfs_handle_struct *handle,
 
 struct vfs_cc_state {
 	off_t copied;
-	uint8_t buf[65536];
+	uint8_t *buf;
 };
 
 static struct tevent_req *vfswrap_copy_chunk_send(struct vfs_handle_struct *handle,
@@ -1419,6 +1419,12 @@ static struct tevent_req *vfswrap_copy_chunk_send(struct vfs_handle_struct *hand
 		return NULL;
 	}
 
+	vfs_cc_state->buf = talloc_array(vfs_cc_state, uint8_t,
+					 MIN(num, 8*1024*1024));
+	if (tevent_req_nomem(vfs_cc_state->buf, req)) {
+		return tevent_req_post(req, ev);
+	}
+
 	status = vfs_stat_fsp(src_fsp);
 	if (tevent_req_nterror(req, status)) {
 		return tevent_req_post(req, ev);
@@ -1444,7 +1450,7 @@ static struct tevent_req *vfswrap_copy_chunk_send(struct vfs_handle_struct *hand
 		struct lock_struct lck;
 		int saved_errno;
 
-		off_t this_num = MIN(sizeof(vfs_cc_state->buf),
+		off_t this_num = MIN(talloc_array_length(vfs_cc_state->buf),
 				     num - vfs_cc_state->copied);
 
 		if (src_fsp->op == NULL) {
-- 
2.1.0