On Thu 11-06-15 15:41:11, Josef Bacik wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> wait_sb_inodes() current does a walk of all inodes in the filesystem
> to find dirty one to wait on during sync. This is highly
> inefficient and wastes a lot of CPU when there are lots of clean
> cached inodes that we don't need to wait on.
>
> To avoid this "all inode" walk, we need to track inodes that are
> currently under writeback that we need to wait for. We do this by
> adding inodes to a writeback list on the bdi when the mapping is
> first tagged as having pages under writeback. wait_sb_inodes() can
> then walk this list of "inodes under IO" and wait specifically just
> for the inodes that the current sync(2) needs to wait for.
>
> To avoid needing all the realted locking to be safe against
> interrupts, Jan Kara suggested that we be lazy about removal from
> the writeback list. That is, we don't remove inodes from the
> writeback list on IO completion, but do it directly during a
> wait_sb_inodes() walk.
>
> This means that the a rare sync(2) call will have some work to do
> skipping clean inodes However, in the current problem case of
> concurrent sync workloads, concurrent wait_sb_inodes() calls only
> walk the very recently dispatched inodes and hence should have very
> little work to do.
>
> This also means that we have to remove the inodes from the writeback
> list during eviction. Do this in inode_wait_for_writeback() once
> all writeback on the inode is complete.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Signed-off-by: Josef Bacik <jbacik@xxxxxx>
I don't think you noticed comments I did when you last posted this
series:
> /*
> - * Wait for writeback on an inode to complete. Caller must have inode pinned.
> + * Wait for writeback on an inode to complete during eviction. Caller must have
> + * inode pinned.
> */
> void inode_wait_for_writeback(struct inode *inode)
> {
> + BUG_ON(!(inode->i_state & I_FREEING));
> +
> spin_lock(&inode->i_lock);
> __inode_wait_for_writeback(inode);
> spin_unlock(&inode->i_lock);
> +
> + /*
> + * bd_inode's will have already had the bdev free'd so don't bother
> + * doing the bdi_clear_inode_writeback.
> + */
> + if (!sb_is_blkdev_sb(inode->i_sb))
> + bdi_clear_inode_writeback(inode_to_bdi(inode), inode);
> }
Why do we bother with not putting bdev inode back?
...
> spin_lock(&inode->i_lock);
> - if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
> - (mapping->nrpages == 0)) {
> + if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
> + list_move(&inode->i_wb_list, &bdi->wb.b_writeback);
Indenting is broken here...
> spin_unlock(&inode->i_lock);
> + cond_resched_lock(&bdi->wb.list_lock);
> continue;
> }
> __iget(inode);
> spin_unlock(&inode->i_lock);
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
