I still have a local branch around with several optimizations (from
the time I was a volunteer), with one of them being precisely to
avoid
unnecessary truncate commands, however I never ended up getting to
the
point of doing benchmarks.
Pasted below and at
https://www.friendpaste.com/1J1TuXf2wlU1125mX57k4r
commit 362290ea03b52e4ce4edb43453a51a3b1f1cd33f
Author: Filipe David Borba Manana <fdman...@gmail.com>
Date: Sat Apr 5 22:34:45 2014 +0100
Btrfs: send, don't issue unnecessary file truncate commands
Every time a file is created or updated, send (either incremental
or not) always
issues a file truncate command. In several commons scenarios this
truncate is not
needed and yet it was still issued all the time. The unnecessary
cases where the
truncate command is not needed are:
* We have a new file, and its last extent isn't a hole, so that
its last write
command ends at the file's size;
* For an incremental send, we updated in place an existing file,
without changing
its size;
* For an incremental send, we updated the file, increased its
size, and the last
file extent item doesn't correspond to a hole. In this case the
last write
command against the file ends at the file's new size;
* For an incremental send, we didn't update the file's data at
all, we only changed
its mode, group or access/update timestamps.
Therefore don't send truncate commands for these cases, reducing
the stream's size
and saving time.
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index fa378c7ebffd..46f52b4bbc21 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -120,6 +120,7 @@ struct send_ctx {
u64 cur_inode_mode;
u64 cur_inode_rdev;
u64 cur_inode_last_extent;
+ u64 cur_inode_max_write_end;
u64 send_progress;
u64 total_data_size;
@@ -4494,6 +4495,8 @@ static int send_hole(struct send_ctx *sctx, u64
end)
break;
offset += len;
}
+ sctx->cur_inode_max_write_end = max(offset,
+ sctx->cur_inode_max_write_end);
tlv_put_failure:
fs_path_free(p);
return ret;
@@ -4529,6 +4532,10 @@ static int send_write_or_clone(struct send_ctx
*sctx,
len = btrfs_file_extent_num_bytes(path->nodes[0], ei);
}
+ if (offset >= sctx->cur_inode_size) {
+ ret = 0;
+ goto out;
+ }
if (offset + len > sctx->cur_inode_size)
len = sctx->cur_inode_size - offset;
if (len == 0) {
@@ -4560,6 +4567,8 @@ static int send_write_or_clone(struct send_ctx
*sctx,
}
ret = 0;
}
+ sctx->cur_inode_max_write_end = max(offset + len,
+ sctx->cur_inode_max_write_end);
out:
return ret;
}
@@ -4982,6 +4991,7 @@ static int finish_inode_if_needed(struct
send_ctx *sctx, int at_end)
u64 right_gid;
int need_chmod = 0;
int need_chown = 0;
+ int need_truncate = 1;
int pending_move = 0;
int refs_processed = 0;
@@ -5022,9 +5032,13 @@ static int finish_inode_if_needed(struct
send_ctx *sctx, int at_end)
need_chown = 1;
if (!S_ISLNK(sctx->cur_inode_mode))
need_chmod = 1;
+ if (sctx->cur_inode_max_write_end == sctx->cur_inode_size)
+ need_truncate = 0;
} else {
+ u64 old_size;
+
ret = get_inode_info(sctx->parent_root, sctx->cur_ino,
- NULL, NULL, &right_mode, &right_uid,
+ &old_size, NULL, &right_mode, &right_uid,
&right_gid, NULL);
if (ret < 0)
goto out;
@@ -5033,6 +5047,13 @@ static int finish_inode_if_needed(struct
send_ctx *sctx, int at_end)
need_chown = 1;
if (!S_ISLNK(sctx->cur_inode_mode) && left_mode != right_mode)
need_chmod = 1;
+
+ if (old_size == sctx->cur_inode_size &&
+ sctx->cur_inode_max_write_end <= sctx->cur_inode_size)
+ need_truncate = 0;
+ else if (sctx->cur_inode_size > old_size &&
+ sctx->cur_inode_max_write_end == sctx->cur_inode_size)
+ need_truncate = 0;
}
truncate_inode:
@@ -5052,10 +5073,13 @@ static int finish_inode_if_needed(struct
send_ctx *sctx, int at_end)
goto out;
}
}
- ret = send_truncate(sctx, sctx->cur_ino, sctx->cur_inode_gen,
- sctx->cur_inode_size);
- if (ret < 0)
- goto out;
+ if (need_truncate) {
+ ret = send_truncate(sctx, sctx->cur_ino,
+ sctx->cur_inode_gen,
+ sctx->cur_inode_size);
+ if (ret < 0)
+ goto out;
+ }
}
if (need_chown) {
@@ -5110,6 +5134,7 @@ static int changed_inode(struct send_ctx *sctx,
sctx->cur_ino = key->objectid;
sctx->cur_inode_new_gen = 0;
sctx->cur_inode_last_extent = (u64)-1;
+ sctx->cur_inode_max_write_end = 0;
/*
* Set send_progress to current inode. This will tell all
get_cur_xxx
Thanks,
Qu
Overall performance improves by 102 percent when sending 790000
small files.
original: 32m45.311s
patch: 16m8.387s
Signed-off-by: Robbie Ko <robbi...@synology.com>
---
fs/btrfs/send.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 20d3300..7ae2347 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5857,10 +5857,6 @@ static int finish_inode_if_needed(struct
send_ctx *sctx, int at_end)
goto out;
}
}
- ret = send_truncate(sctx, sctx->cur_ino,
sctx->cur_inode_gen,
- sctx->cur_inode_size);
- if (ret < 0)
- goto out;
}
if (need_chown) {
@@ -6044,6 +6040,15 @@ static int changed_inode(struct send_ctx
*sctx,
sctx->left_path->nodes[0],
left_ii);
}
}
+ if (result == BTRFS_COMPARE_TREE_NEW ||
+ result == BTRFS_COMPARE_TREE_CHANGED) {
+ if (S_ISREG(sctx->cur_inode_mode)) {
+ ret = send_truncate(sctx, sctx->cur_ino,
sctx->cur_inode_gen,
+
sctx->cur_inode_size);
+ if (ret < 0)
+ goto out;
+ }
+ }
out:
return ret;
