On 11/22/2016 04:20 AM, Wang Xiaoguang wrote:
hello,
On 11/22/2016 12:39 AM, David Sterba wrote:
On Tue, Nov 08, 2016 at 05:30:58PM +0800, Wang Xiaoguang wrote:
The current limit of number of asynchronous delalloc pages is (10 *
SZ_1M).
For 4K page, the total ram bytes would be 40G, very big value, I
think in
most cases, this limit will not work, here I set limit of the number of
asynchronous delalloc pages to SZ_1M(4GB ram bytes).
Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8e3a5a2..3a910f6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1158,7 +1158,7 @@ static int cow_file_range_async(struct inode
*inode, struct page *locked_page,
struct btrfs_root *root = BTRFS_I(inode)->root;
unsigned long nr_pages;
u64 cur_end;
- int limit = 10 * SZ_1M;
+ int limit = SZ_1M;
This looks like mismatch in units, the limit seems to be "10MiB" but
it's used to compare async_delalloc_pages, which is in pages. I'm not
sure what's the expected value for limit, as 10MiB is too small.
There are such codes in cow_file_range_async()
nr_pages = (cur_end - start + PAGE_SIZE) >> PAGE_SHIFT;
atomic_add(nr_pages, &root->fs_info->async_delalloc_pages);
So here the real limit is 10 * SZ_1M * 4096, 40GB memory, I think this
value is too big, so modify it to 4GB.
I don't disagree that its too big, but if the rest of the
dirty/writeback throttling infra in the kernel is enough, we can just
delete this limit completely.
-chris
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