From: Christoph Hellwig Date: Sun, 18 Jul 2010 21:17:11 +0000 (+0000) Subject: xfs simplify and speed up direct I/O completions X-Git-Tag: firefly_0821_release~9833^2~1324^2~1 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=209fb87a259ead17e966627b7f053d16a96898da;p=firefly-linux-kernel-4.4.55.git xfs simplify and speed up direct I/O completions Our current handling of direct I/O completions is rather suboptimal, because we defer it to a workqueue more often than needed, and we perform a much to aggressive flush of the workqueue in case unwritten extent conversions happen. This patch changes the direct I/O reads to not even use a completion handler, as we don't bother to use it at all, and to perform the unwritten extent conversions in caller context for synchronous direct I/O. For a small I/O size direct I/O workload on a consumer grade SSD, such as the untar of a kernel tree inside qemu this patch gives speedups of about 5%. Getting us much closer to the speed of a native block device, or a fully allocated XFS file. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Signed-off-by: Alex Elder --- diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c index 13622d5ba068..d24e78f32f3e 100644 --- a/fs/xfs/linux-2.6/xfs_aops.c +++ b/fs/xfs/linux-2.6/xfs_aops.c @@ -202,23 +202,17 @@ xfs_setfilesize( } /* - * Schedule IO completion handling on a xfsdatad if this was - * the final hold on this ioend. If we are asked to wait, - * flush the workqueue. + * Schedule IO completion handling on the final put of an ioend. */ STATIC void xfs_finish_ioend( - xfs_ioend_t *ioend, - int wait) + struct xfs_ioend *ioend) { if (atomic_dec_and_test(&ioend->io_remaining)) { - struct workqueue_struct *wq; - - wq = (ioend->io_type == IO_UNWRITTEN) ? - xfsconvertd_workqueue : xfsdatad_workqueue; - queue_work(wq, &ioend->io_work); - if (wait) - flush_workqueue(wq); + if (ioend->io_type == IO_UNWRITTEN) + queue_work(xfsconvertd_workqueue, &ioend->io_work); + else + queue_work(xfsdatad_workqueue, &ioend->io_work); } } @@ -262,7 +256,7 @@ xfs_end_io( */ if (error == EAGAIN) { atomic_inc(&ioend->io_remaining); - xfs_finish_ioend(ioend, 0); + xfs_finish_ioend(ioend); /* ensure we don't spin on blocked ioends */ delay(1); } else { @@ -272,6 +266,17 @@ xfs_end_io( } } +/* + * Call IO completion handling in caller context on the final put of an ioend. + */ +STATIC void +xfs_finish_ioend_sync( + struct xfs_ioend *ioend) +{ + if (atomic_dec_and_test(&ioend->io_remaining)) + xfs_end_io(&ioend->io_work); +} + /* * Allocate and initialise an IO completion structure. * We need to track unwritten extent write completion here initially. @@ -353,7 +358,7 @@ xfs_end_bio( bio->bi_end_io = NULL; bio_put(bio); - xfs_finish_ioend(ioend, 0); + xfs_finish_ioend(ioend); } STATIC void @@ -495,7 +500,7 @@ xfs_submit_ioend( } if (bio) xfs_submit_ioend_bio(wbc, ioend, bio); - xfs_finish_ioend(ioend, 0); + xfs_finish_ioend(ioend); } while ((ioend = next) != NULL); } @@ -1406,70 +1411,56 @@ xfs_get_blocks_direct( return __xfs_get_blocks(inode, iblock, bh_result, create, 1); } +/* + * Complete a direct I/O write request. + * + * If the private argument is non-NULL __xfs_get_blocks signals us that we + * need to issue a transaction to convert the range from unwritten to written + * extents. In case this is regular synchronous I/O we just call xfs_end_io + * to do this and we are done. But in case this was a successfull AIO + * request this handler is called from interrupt context, from which we + * can't start transactions. In that case offload the I/O completion to + * the workqueues we also use for buffered I/O completion. + */ STATIC void -xfs_end_io_direct( - struct kiocb *iocb, - loff_t offset, - ssize_t size, - void *private, - int ret, - bool is_async) +xfs_end_io_direct_write( + struct kiocb *iocb, + loff_t offset, + ssize_t size, + void *private, + int ret, + bool is_async) { - xfs_ioend_t *ioend = iocb->private; - bool complete_aio = is_async; + struct xfs_ioend *ioend = iocb->private; /* - * Non-NULL private data means we need to issue a transaction to - * convert a range from unwritten to written extents. This needs - * to happen from process context but aio+dio I/O completion - * happens from irq context so we need to defer it to a workqueue. - * This is not necessary for synchronous direct I/O, but we do - * it anyway to keep the code uniform and simpler. - * - * Well, if only it were that simple. Because synchronous direct I/O - * requires extent conversion to occur *before* we return to userspace, - * we have to wait for extent conversion to complete. Look at the - * iocb that has been passed to us to determine if this is AIO or - * not. If it is synchronous, tell xfs_finish_ioend() to kick the - * workqueue and wait for it to complete. - * - * The core direct I/O code might be changed to always call the - * completion handler in the future, in which case all this can - * go away. + * blockdev_direct_IO can return an error even after the I/O + * completion handler was called. Thus we need to protect + * against double-freeing. */ + iocb->private = NULL; + ioend->io_offset = offset; ioend->io_size = size; - if (ioend->io_type == IO_READ) { - xfs_finish_ioend(ioend, 0); - } else if (private && size > 0) { - if (is_async) { + if (private && size > 0) + ioend->io_type = IO_UNWRITTEN; + + if (is_async) { + /* + * If we are converting an unwritten extent we need to delay + * the AIO completion until after the unwrittent extent + * conversion has completed, otherwise do it ASAP. + */ + if (ioend->io_type == IO_UNWRITTEN) { ioend->io_iocb = iocb; ioend->io_result = ret; - complete_aio = false; - xfs_finish_ioend(ioend, 0); } else { - xfs_finish_ioend(ioend, 1); + aio_complete(iocb, ret, 0); } + xfs_finish_ioend(ioend); } else { - /* - * A direct I/O write ioend starts it's life in unwritten - * state in case they map an unwritten extent. This write - * didn't map an unwritten extent so switch it's completion - * handler. - */ - ioend->io_type = IO_NEW; - xfs_finish_ioend(ioend, 0); + xfs_finish_ioend_sync(ioend); } - - /* - * blockdev_direct_IO can return an error even after the I/O - * completion handler was called. Thus we need to protect - * against double-freeing. - */ - iocb->private = NULL; - - if (complete_aio) - aio_complete(iocb, ret, 0); } STATIC ssize_t @@ -1480,23 +1471,26 @@ xfs_vm_direct_IO( loff_t offset, unsigned long nr_segs) { - struct file *file = iocb->ki_filp; - struct inode *inode = file->f_mapping->host; - struct block_device *bdev; - ssize_t ret; - - bdev = xfs_find_bdev_for_inode(inode); - - iocb->private = xfs_alloc_ioend(inode, rw == WRITE ? - IO_UNWRITTEN : IO_READ); - - ret = blockdev_direct_IO_no_locking(rw, iocb, inode, bdev, iov, - offset, nr_segs, - xfs_get_blocks_direct, - xfs_end_io_direct); + struct inode *inode = iocb->ki_filp->f_mapping->host; + struct block_device *bdev = xfs_find_bdev_for_inode(inode); + ssize_t ret; + + if (rw & WRITE) { + iocb->private = xfs_alloc_ioend(inode, IO_NEW); + + ret = blockdev_direct_IO_no_locking(rw, iocb, inode, bdev, iov, + offset, nr_segs, + xfs_get_blocks_direct, + xfs_end_io_direct_write); + if (ret != -EIOCBQUEUED && iocb->private) + xfs_destroy_ioend(iocb->private); + } else { + ret = blockdev_direct_IO_no_locking(rw, iocb, inode, bdev, iov, + offset, nr_segs, + xfs_get_blocks_direct, + NULL); + } - if (unlikely(ret != -EIOCBQUEUED && iocb->private)) - xfs_destroy_ioend(iocb->private); return ret; }