On 11/9/2015 2:15 PM, Bjorn Helgaas wrote:
I talked to our performance team. They are saying that max read
>request does not gain you much compared to max payload size single
>direction but it helps tremendously if you are moving data forth and
>back between the card. I don't have real numbers though.
I'm not enough of a hardware or performance person to visualize how
MRRS makes a tremendous difference in this situation. Sample
timelines comparing small vs. large MRRS would help everybody
understand what's happening here.
Bjorn
The LSI SAS 9211i card supports 4k maximum read request size. I manually
forced this to 4k instead of the maximum payload size of the platform on
both the host bridge and the endpoint.
I did a quick test with:
dd if=/dev/zero of=/dev/sda bs=1G count=1
It gave me %9 higher write performance.
--
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
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