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Message-ID: <87f94c370903120913p6ec23c84pdff404c0e207b56f@mail.gmail.com>
Date: Thu, 12 Mar 2009 12:13:27 -0400
From: Greg Freemyer <greg.freemyer@...il.com>
To: Sandeep K Sinha <sandeepksinha@...il.com>
Cc: ext4 <linux-ext4@...r.kernel.org>,
Kernel Newbies <kernelnewbies@...linux.org>,
Manish Katiyar <mkatiyar@...il.com>
Subject: Re: [ext2/ext3] Re-allocation of blocks for an inode
On Thu, Mar 12, 2009 at 11:16 AM, Sandeep K Sinha
<sandeepksinha@...il.com> wrote:
> Hi all,
>
> I am listing above two codes for re-allocating new blocks for a given inode.
>
> These code snippets are specific to ext2.
> The problem here is that it is performing slower than cp and dd.
>
> Can anyone help in determining what can be the possible reason(s) ?
Excessive use of sync_dirty_buffer();
You're calling it for every single block you copy. Pretty sure it is a
very aggressive call that forces the data out to the disk immediately,
thus the benefits of caching and elevators are lost. And those are
big benefits.
Greg
>
> 1. MEMCPY
> =======
>
>
>
> src_ind = ext2_iget (sb, inum);
> if (!src_ind) {
> printk (KERN_DEBUG "\n OHSM Source Inode Not Found ");
> goto out_err;
> }
>
> /* Getting the ghost inode */
> dest_ind = ext2_new_inode (nd.path.dentry->d_inode, src_ind->i_mode);
> if (IS_ERR(dest_ind)) {
> printk (KERN_ALERT "\n OHSM destination inode unable to allocate.
> err = %ld", PTR_ERR(dest_ind));
> goto out_err;
> }
>
> /* Locking the source inode using mutex */
> mutex_lock (&src_ind->i_mutex);
>
> /* Get the source inode size and number of blocks */
> i_size = i_size_read(src_ind);
>
> /* Calculating number of block to allocate for ghost inode */
> nblocks = (i_size >> EXT2_BLOCK_SIZE_BITS(sb)) +
> ((i_size & (sb->s_blocksize - 1)) ? 1 : 0);
>
> memset(&dest_bh, 0, sizeof(struct buffer_head));
> memset(&src_bh, 0, sizeof(struct buffer_head));
> for (done = 0; done < nblocks; done++) {
>
> err = ext2_get_block (src_ind, done, &src_bh, 0);
> if (err < 0) {
> printk (KERN_DEBUG "\n error getting blocks ret_val = %d",err);
> goto unlock;
> }
>
> dest_bh.b_state = 0;
> err = ext2_get_block (dest_ind, done, &dest_bh, 1);
> if (err < 0) {
> printk (KERN_DEBUG "\n error getting blocks ret_val = %d",err);
> goto unlock;
> }
>
> if (!buffer_mapped(&src_bh)){
> printk (KERN_DEBUG "\nHOLE ");
> continue;
> }
>
> src_bhptr = sb_bread(sb, src_bh.b_blocknr);
> if (!src_bhptr)
> goto unlock;
>
> dst_bhptr = sb_bread(sb, dest_bh.b_blocknr);
> if (!dst_bhptr)
> goto unlock;
>
> lock_buffer(dst_bhptr);
> memcpy(dst_bhptr->b_data,src_bhptr->b_data,src_bhptr->b_size);
> unlock_buffer(dst_bhptr);
>
> mark_buffer_dirty(dst_bhptr);
> sync_dirty_buffer(dst_bhptr);
>
> brelse(src_bhptr);
> brelse(dst_bhptr);
>
> }
>
> for (blk_index = 0; blk_index < 15; blk_index++) {
> if (EXT2_I (dest_ind)->i_data[blk_index]){
> swap = EXT2_I (src_ind)->i_data[blk_index];
> EXT2_I (src_ind)->i_data[blk_index] =
> EXT2_I (dest_ind)->i_data[blk_index];
> EXT2_I (dest_ind)->i_data[blk_index] = swap;
> }
> }
>
> dest_ind->i_blocks = src_ind->i_blocks ;
> mark_inode_dirty (src_ind);
> sync_mapping_buffers(src_ind->i_mapping);
> ohsm_sync_inode(src_ind);
> iput(src_ind);
>
> dest_ind->i_nlink = 0;
> iput(dest_ind);
> mutex_unlock (&src_ind->i_mutex);
> goto out_err;
>
> unlock:
> brelse(src_bhptr);
> brelse(dst_bhptr);
> mutex_unlock (&src_ind->i_mutex);
>
> out_err:
> path_put (&nd.path);
> return;
>
>
>
> 2. PAGEFLIP
> ========
>
>
> /* Get the source inode */
>
> src_ind = ext2_iget (sb, inum);
> if (!src_ind) {
> printk (KERN_DEBUG "\n OHSM Source Inode Not Found ");
> goto out_err;
> }
>
> /* Getting the ghost inode */
> dest_ind = ext2_new_inode (nd.path.dentry->d_inode, src_ind->i_mode);
> if (IS_ERR(dest_ind)) {
> printk (KERN_ALERT "\n destination inode unable to allocate. err =
> %ld", PTR_ERR(dest_ind));
> goto out_err;
> }
>
> /* Locking the source inode using mutex */
> mutex_lock (&src_ind->i_mutex);
>
> /* Get the source inode size and number of blocks */
> i_size = i_size_read(src_ind);
>
> /* Calculating number of block to allocate for ghost inode */
> nblocks = (i_size >> EXT2_BLOCK_SIZE_BITS(sb)) +
> ((i_size & (sb->s_blocksize - 1)) ? 1 : 0);
>
>
> memset(&dest_bh, 0, sizeof(struct buffer_head));
> memset(&src_bh, 0, sizeof(struct buffer_head));
> for (done = 0; done < nblocks; done++) {
>
> err = ext2_get_block (src_ind, done, &src_bh, 0);
> if (err < 0) {
> printk (KERN_DEBUG "\n error getting blocks ret_val = %d",err);
> goto unlock;
> }
>
> dest_bh.b_state = 0;
> err = ext2_get_block (dest_ind, done, &dest_bh, 1);
> if (err < 0) {
> printk (KERN_DEBUG "\n error getting blocks ret_val = %d",err);
> goto unlock;
> }
>
> if (!buffer_mapped(&src_bh)){
> printk (KERN_DEBUG "\nHOLE ");
> continue;
> }
>
> src_bhptr = sb_bread(sb, src_bh.b_blocknr);
> if (!src_bhptr)
> goto unlock;
>
> dst_bhptr = sb_bread(sb, dest_bh.b_blocknr);
> if (!dst_bhptr)
> goto unlock;
>
> lock_buffer(dst_bhptr);
> oldpage = dst_bhptr->b_page;
> olddata = dst_bhptr->b_data;
> dst_bhptr->b_data = src_bhptr->b_data;
> dst_bhptr->b_page = src_bhptr->b_page;
> flush_dcache_page(dst_bhptr->b_page);
> unlock_buffer(dst_bhptr);
>
> mark_buffer_dirty(dst_bhptr);
> sync_dirty_buffer(dst_bhptr);
>
> if(buffer_uptodate(dst_bhptr)) {
> dst_bhptr->b_page = oldpage;
> dst_bhptr->b_data = olddata;
> }
>
> brelse(src_bhptr);
> brelse(dst_bhptr);
> }
>
> for (blk_index = 0; blk_index < 15; blk_index++) {
> if (EXT2_I (dest_ind)->i_data[blk_index]){
> swap = EXT2_I (src_ind)->i_data[blk_index];
> EXT2_I (src_ind)->i_data[blk_index] =
> EXT2_I (dest_ind)->i_data[blk_index];
> EXT2_I (dest_ind)->i_data[blk_index] = swap;
> }
> }
>
> dest_ind->i_blocks = src_ind->i_blocks ;
> mark_inode_dirty (src_ind);
> sync_mapping_buffers(src_ind->i_mapping);
> ohsm_sync_inode(src_ind);
> iput(src_ind);
>
> dest_ind->i_nlink = 0;
> iput(dest_ind);
> mutex_unlock (&src_ind->i_mutex);
> goto out_err;
>
> unlock:
> brelse(src_bhptr);
> brelse(dst_bhptr);
> mutex_unlock (&src_ind->i_mutex);
>
> out_err:
> path_put (&nd.path);
> return;
> }
>
>
>
> --
> Regards,
> Sandeep.
>
>
>
>
>
>
> “To learn is to change. Education is a process that changes the learner.”
>
--
Greg Freemyer
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf
The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com
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