** Changed in: linux (Ubuntu Bionic)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1777727
Title:
hisi_sas: improve read performance by pre-allocating slot DMA buffers
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Bionic:
Fix Committed
Bug description:
[Impact]
Read performance is ~9% slower than it could be, as measured by the iozone3
benchmark.
[Test Case]
iozone -a
I suggest collecting 5 runs of this, with and without the patch, and
generating a report using:
https://github.com/Rovanion/iozone-results-comparator/wiki/Overview
[Fix]
Apply a patch queued in the scsi tree that pre-allocates DMA slot buffers.
[Regression Risk]
As called out in the commit log, the trade-off here is static memory usage,
which could grow by ~17MB. However, as also noted, this method actually uses
*less* memory than the baseline when all slots are allocated (32MB). (Ubuntu
uses a 4K kernel).
The required fixes are localized to the hisi_sas driver. This driver
is only used by two platforms supported by Ubuntu: HiSilicon D05 and
HiSilicon D06. We will directly verify these fixes on those platforms.
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