Re: [PATCH 18/20] xfs: remove unused buffer cache APIs

Christoph Hellwig
2019-06-05T15:12:36Z

On Tue, Jun 04, 2019 at 04:24:42PM +1000, Dave Chinner wrote:
> > @@ -1258,7 +1192,7 @@ xfs_buf_ioend_async(
> > struct xfs_buf *bp)
> > {
> > INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
> > - queue_work(bp->b_ioend_wq, &bp->b_ioend_work);
> > + queue_work(bp->b_target->bt_mount->m_buf_workqueue, &bp->b_ioend_work);
> > }
>
> It'd be nice to keep bp->b_ioend_wq to avoid pointer chasing here.
> Perhaps we could set it up in _xfs_buf_alloc() where we are pretty
> much guaranteed to have the xfs_mount hot in cache, and then it's
> set for the life of the buffer. Just a thought, but either way:

We'd need to benchmark this particular case, but the bloat to
the xfs_buf structure probably cancels out at least one pointer
dereference. That being said we probably could at least remove
one indirection without bloating the buf, I'll take a look at that.