From 27bc446e2def38db3244a6eb4bb1d6312936610a Mon Sep 17 00:00:00 2001 From: brookxu Date: Mon, 17 Aug 2020 15:36:15 +0800 Subject: ext4: limit the length of per-inode prealloc list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the scenario of writing sparse files, the per-inode prealloc list may be very long, resulting in high overhead for ext4_mb_use_preallocated(). To circumvent this problem, we limit the maximum length of per-inode prealloc list to 512 and allow users to modify it. After patching, we observed that the sys ratio of cpu has dropped, and the system throughput has increased significantly. We created a process to write the sparse file, and the running time of the process on the fixed kernel was significantly reduced, as follows: Running time on unfixed kernel： [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat real 0m2.051s user 0m0.008s sys 0m2.026s Running time on fixed kernel： [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat real 0m0.471s user 0m0.004s sys 0m0.395s Signed-off-by: Chunguang Xu Link: https://lore.kernel.org/r/d7a98178-056b-6db5-6bce-4ead23f4a257@gmail.com Signed-off-by: Theodore Ts'o --- fs/ext4/indirect.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/ext4/indirect.c') diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index 433ca8415c5a..80c9f33800be 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -696,7 +696,7 @@ static int ext4_ind_trunc_restart_fn(handle_t *handle, struct inode *inode, * i_mutex. So we can safely drop the i_data_sem here. */ BUG_ON(EXT4_JOURNAL(inode) == NULL); - ext4_discard_preallocations(inode); + ext4_discard_preallocations(inode, 0); up_write(&EXT4_I(inode)->i_data_sem); *dropped = 1; return 0; -- cgit v1.2.3