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Subject[PATCH 1/7] [I/OAT] Push pending transactions to hardware more frequently
Date
Every 20 descriptors turns out to be to few append commands with
newer/faster CPUs. Pushing every 4 still cuts down on MMIO writes to an
acceptable level without letting the DMA engine run out of work.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
---
drivers/dma/ioatdma.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/dma/ioatdma.c b/drivers/dma/ioatdma.c
index dbd4d6c..be4fdd7 100644
--- a/drivers/dma/ioatdma.c
+++ b/drivers/dma/ioatdma.c
@@ -310,7 +310,7 @@ static dma_cookie_t do_ioat_dma_memcpy(s
list_splice_init(&new_chain, ioat_chan->used_desc.prev);

ioat_chan->pending += desc_count;
- if (ioat_chan->pending >= 20) {
+ if (ioat_chan->pending >= 4) {
append = 1;
ioat_chan->pending = 0;
}
@@ -818,7 +818,7 @@ static void __devexit ioat_remove(struct
}

/* MODULE API */
-MODULE_VERSION("1.7");
+MODULE_VERSION("1.9");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Intel Corporation");

-
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