From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: [GIT PATCH] ioat2: fix performance regression Date: Wed, 13 Oct 2010 16:03:44 -0700 Message-ID: <20101013230248.32594.35857.stgit@localhost6.localdomain6> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Dave Jiang , Linus Walleij , netdev@vger.kernel.org, Maciej Sosnowski , Jesse Brandeburg , linux-kernel@vger.kernel.org, stable@kernel.org, Richard Scobie To: akpm@linux-foundation.org, torvalds@linux-foundation.org Return-path: Received: from mga11.intel.com ([192.55.52.93]:14513 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753542Ab0JMXAh (ORCPT ); Wed, 13 Oct 2010 19:00:37 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Commit 0793448 "DMAENGINE: generic channel status v2" changed the interface for how dma channel progress is retrieved. It inadvertently exported an internal helper function ioat_tx_status() instead of ioat_dma_tx_status(). The latter polls the hardware to get the latest completion state, while the helper just evaluates the current state without touching hardware. The effect is that we end up waiting for completion timeouts or descriptor allocation errors before the completion state is updated. iperf (before fix): [SUM] 0.0-41.3 sec 364 MBytes 73.9 Mbits/sec iperf (after fix): [SUM] 0.0- 4.5 sec 499 MBytes 940 Mbits/sec This is a regression starting with 2.6.35. Cc: Cc: Dave Jiang Cc: Jesse Brandeburg Cc: Linus Walleij Cc: Maciej Sosnowski Reported-by: Richard Scobie Signed-off-by: Dan Williams --- Late breaking fix that can hopefully get into 2.6.36. I will queue a cleanup to clarify this confusing naming convention for 2.6.37. Also available via git: git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git fixes Dan Williams (1): ioat2: fix performance regression drivers/dma/ioat/dma_v2.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c index 216f9d3..effd140 100644 --- a/drivers/dma/ioat/dma_v2.c +++ b/drivers/dma/ioat/dma_v2.c @@ -879,7 +879,7 @@ int __devinit ioat2_dma_probe(struct ioatdma_device *device, int dca) dma->device_issue_pending = ioat2_issue_pending; dma->device_alloc_chan_resources = ioat2_alloc_chan_resources; dma->device_free_chan_resources = ioat2_free_chan_resources; - dma->device_tx_status = ioat_tx_status; + dma->device_tx_status = ioat_dma_tx_status; err = ioat_probe(device); if (err)