Re: [PATCH v2 0/4] Optimise 64-bit IOVA allocations
From: Leizhen (ThunderTown)
Date: Wed Jul 26 2017 - 07:18:34 EST
On 2017/7/26 19:08, Joerg Roedel wrote:
> Hi Robin.
>
> On Fri, Jul 21, 2017 at 12:41:57PM +0100, Robin Murphy wrote:
>> Hi all,
>>
>> In the wake of the ARM SMMU optimisation efforts, it seems that certain
>> workloads (e.g. storage I/O with large scatterlists) probably remain quite
>> heavily influenced by IOVA allocation performance. Separately, Ard also
>> reported massive performance drops for a graphical desktop on AMD Seattle
>> when enabling SMMUs via IORT, which we traced to dma_32bit_pfn in the DMA
>> ops domain getting initialised differently for ACPI vs. DT, and exposing
>> the overhead of the rbtree slow path. Whilst we could go around trying to
>> close up all the little gaps that lead to hitting the slowest case, it
>> seems a much better idea to simply make said slowest case a lot less slow.
>
> Do you have some numbers here? How big was the impact before these
> patches and how is it with the patches?
Here are some numbers:
(before)$ iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 4] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 35898
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.2 sec 7.88 MBytes 6.48 Mbits/sec
[ 5] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 35900
[ 5] 0.0-10.3 sec 7.88 MBytes 6.43 Mbits/sec
[ 4] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 35902
[ 4] 0.0-10.3 sec 7.88 MBytes 6.43 Mbits/sec
(after)$ iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 4] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 36330
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 1.09 GBytes 933 Mbits/sec
[ 5] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 36332
[ 5] 0.0-10.0 sec 1.10 GBytes 939 Mbits/sec
[ 4] local 192.168.1.106 port 5001 connected with 192.168.1.198 port 36334
[ 4] 0.0-10.0 sec 1.10 GBytes 938 Mbits/sec
>
>
> Joerg
>
>
> .
>
--
Thanks!
BestRegards