Messages in this thread Patch in this message | | | Subject | [GIT PATCH] ioat2: fix performance regression | From | Dan Williams <> | Date | Wed, 13 Oct 2010 16:03:44 -0700 |
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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: <stable@kernel.org> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Jesse Brandeburg <jesse.brandeburg@intel.com> Cc: Linus Walleij <linus.walleij@stericsson.com> Cc: Maciej Sosnowski <maciej.sosnowski@intel.com> Reported-by: Richard Scobie <richard@sauce.co.nz> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- 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)
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