Re: How git affects kernel.org performance
From: Fengguang Wu <hidden>
Date: 2007-01-09 07:59:29
Also in:
linux-ext4, lkml
On Mon, Jan 08, 2007 at 07:58:19AM -0500, Theodore Tso wrote:
On Mon, Jan 08, 2007 at 08:35:55AM +0530, Suparna Bhattacharya wrote:quoted
quoted
Yeah, slowly-growing directories will get splattered all over the disk. Possible short-term fixes would be to just allocate up to (say) eight blocks when we grow a directory by one block. Or teach the directory-growth code to use ext3 reservations. Longer-term people are talking about things like on-disk rerservations. But I expect directories are being forgotten about in all of that.By on-disk reservations, do you mean persistent file preallocation ? (that is explicit preallocation of blocks to a given file) If so, you are right, we haven't really given any thought to the possibility of directories needing that feature.The fastest and probably most important thing to add is some readahead smarts to directories --- both to the htree and non-htree cases. If
Here's is a quick hack to practice the directory readahead idea. Comments are welcome, it's a freshman's work :) Regards, Wu --- fs/ext3/dir.c | 22 ++++++++++++++++++++++ fs/ext3/inode.c | 2 +- 2 files changed, 23 insertions(+), 1 deletion(-)
--- linux.orig/fs/ext3/dir.c
+++ linux/fs/ext3/dir.c@@ -94,6 +94,25 @@ int ext3_check_dir_entry (const char * f return error_msg == NULL ? 1 : 0; } +int ext3_get_block(struct inode *inode, sector_t iblock, + struct buffer_head *bh_result, int create); + +static void ext3_dir_readahead(struct file * filp) +{ + struct inode *inode = filp->f_path.dentry->d_inode; + struct address_space *mapping = inode->i_sb->s_bdev->bd_inode->i_mapping; + unsigned long sector; + unsigned long blk; + pgoff_t offset; + + for (blk = 0; blk < inode->i_blocks; blk++) { + sector = blk << (inode->i_blkbits - 9); + sector = generic_block_bmap(inode->i_mapping, sector, ext3_get_block); + offset = sector >> (PAGE_CACHE_SHIFT - 9); + do_page_cache_readahead(mapping, filp, offset, 1); + } +} + static int ext3_readdir(struct file * filp, void * dirent, filldir_t filldir) {
@@ -108,6 +127,9 @@ static int ext3_readdir(struct file * fi sb = inode->i_sb; + if (!filp->f_pos) + ext3_dir_readahead(filp); + #ifdef CONFIG_EXT3_INDEX if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb, EXT3_FEATURE_COMPAT_DIR_INDEX) && --- linux.orig/fs/ext3/inode.c +++ linux/fs/ext3/inode.c
@@ -945,7 +945,7 @@ out: #define DIO_CREDITS (EXT3_RESERVE_TRANS_BLOCKS + 32) -static int ext3_get_block(struct inode *inode, sector_t iblock, +int ext3_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) { handle_t *handle = journal_current_handle();