Re: [PATCH net-next v4 00/18] net/smc: implement virtual ISM extension and loopback-ism

[Niklas Schnelle]

On Sun, 2023-09-24 at 23:16 +0800, Wen Gu wrote:
> Hi, all
> 
> # Background
> 
> SMC-D is now used in IBM z with ISM function to optimize network interconnect
> for intra-CPC communications. Inspired by this, we try to make SMC-D available
> on the non-s390 architecture through a software-simulated virtual ISM device,
> such as loopback-ism device here, to accelerate inter-process or inter-containers
> communication within the same OS.
> 
> # Design
> 
> This patch set includes 4 parts:
> 
>  - Patch #1-#3: decouple ISM device hard code from SMC-D stack.
>  - Patch #4-#8: implement virtual ISM extension defined in SMCv2.1.
>  - Patch #9-#13: implement loopback-ism device.
>  - Patch #14-#18: memory copy optimization for the case using loopback.
> 
> The loopback-ism device is designed as a kernel device and not be limited to
> a specific net namespace, ends of both inter-process connection (1/1' in diagram
> below) or inter-container connection (2/2' in diagram below) will find that peer
> shares the same loopback-ism device during the CLC handshake. Then loopback-ism
> device will be chosen.
> 
>  Container 1 (ns1)                              Container 2 (ns2)
>  +-----------------------------------------+    +-------------------------+
>  | +-------+      +-------+      +-------+ |    |        +-------+        |
>  | | App A |      | App B |      | App C | |    |        | App D |<-+     |
>  | +-------+      +---^---+      +-------+ |    |        +-------+  |(2') |
>  |     |127.0.0.1 (1')|             |192.168.0.11       192.168.0.12|     |
>  |  (1)|   +--------+ | +--------+  |(2)   |    | +--------+   +--------+ |
>  |     `-->|   lo   |-` |  eth0  |<-`      |    | |   lo   |   |  eth0  | |
>  +---------+--|---^-+---+-----|--+---------+    +-+--------+---+-^------+-+
>               |   |           |                                  |
>  Kernel       |   |           |                                  |
>  +----+-------v---+-----------v----------------------------------+---+----+
>  |    |                            TCP                               |    |
>  |    |                                                              |    |
>  |    +--------------------------------------------------------------+    |
>  |                                                                        |
>  |                           +--------------+                             |
>  |                           | smc loopback |                             |
>  +---------------------------+--------------+-----------------------------+
> 
> 
> loopback-ism device allocs RMBs and sndbufs for each connection peer and 'moves'
> data from sndbuf at one end to RMB at the other end. Since communication occurs
> within the same kernel, the sndbuf can be mapped to peer RMB so that the data
> copy in loopback-ism case can be avoided.
> 
>  Container 1 (ns1)                              Container 2 (ns2)
>  +-----------------------------------------+    +-------------------------+
>  | +-------+      +-------+      +-------+ |    |        +-------+        |
>  | | App A |      | App B |      | App C | |    |        | App D |        |
>  | +-------+      +--^----+      +-------+ |    |        +---^---+        |
>  |       |           |               |     |    |            |            |
>  |   (1) |      (1') |           (2) |     |    |       (2') |            |
>  |       |           |               |     |    |            |            |
>  +-------|-----------|---------------|-----+    +------------|------------+
>          |           |               |                       |
>  Kernel  |           |               |                       |
>  +-------|-----------|---------------|-----------------------|------------+
>  | +-----v-+      +-------+      +---v---+               +-------+        |
>  | | snd A |-+    | RMB B |<--+  | snd C |-+          +->| RMB D |        |
>  | +-------+ |    +-------+   |  +-------+ |          |  +-------+        |
>  | +-------+ |    +-------+   |  +-------+ |          |  +-------+        |
>  | | RMB A | |    | snd B |   |  | RMB C | |          |  | snd D |        |
>  | +-------+ |    +-------+   |  +-------+ |          |  +-------+        |
>  |           |               +-------------v+         |                   |
>  |           +-------------->| smc loopback |---------+                   |
>  +---------------------------+--------------+-----------------------------+
> 
> # Benchmark Test
> 
>  * Test environments:
>       - VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem.
>       - SMC sndbuf/RMB size 1MB.
> 
>  * Test object:
>       - TCP: run on TCP loopback.
>       - domain: run on UNIX domain.
>       - SMC lo: run on SMC loopback device.
> 
> 1. ipc-benchmark (see [1])
> 
>  - ./<foo> -c 1000000 -s 100
> 
>                             TCP                  SMC-lo
> Message
> rate (msg/s)              81539                  151251(+85.50%)
> 
> 2. sockperf
> 
>  - serv: <smc_run> taskset -c <cpu> sockperf sr --tcp
>  - clnt: <smc_run> taskset -c <cpu> sockperf { tp | pp } --tcp --msg-size={ 64000 for tp | 14 for pp } -i 127.0.0.1 -t 30
> 
>                             TCP                  SMC-lo
> Bandwidth(MBps)         5313.66                 8270.51(+55.65%)
> Latency(us)               5.806                   3.207(-44.76%)
> 
> 3. nginx/wrk
> 
>  - serv: <smc_run> nginx
>  - clnt: <smc_run> wrk -t 8 -c 1000 -d 30 http://127.0.0.1:80
> 
>                            TCP                   SMC-lo
> Requests/s           194641.79                258656.13(+32.89%)
> 
> 4. redis-benchmark
> 
>  - serv: <smc_run> redis-server
>  - clnt: <smc_run> redis-benchmark -h 127.0.0.1 -q -t set,get -n 400000 -c 200 -d 1024
> 
>                            TCP                   SMC-lo
> GET(Requests/s)       85855.34                115640.35(+34.69%)
> SET(Requests/s)       86337.15                118203.30(+36.90%)
> 
> [1] https://github.com/goldsborough/ipc-bench
> 

Hi Wen Gu,

I've been trying out your series with iperf3, qperf, and uperf on
s390x. I'm using network namespaces with a ConnectX VF from the same
card in each namespace for the initial TCP/IP connection i.e. initially
it goes out to a real NIC even if that can switch internally. All of
these look great for streaming workloads both in terms of performance
and stability. With a Connect-Request-Response workload and uperf
however I've run into issues. The test configuration I use is as
follows:

Client Command:

# host=$ip_server ip netns exec client smc_run uperf -m tcp_crr.xml

Server Command:

# ip netns exec server smc_run uperf -s &> /dev/null

Uperf tcp_crr.xml:

<?xml version="1.0"?>
<profile name="TCP_CRR">
        <group nthreads="12">
                <transaction duration="120">
                        <flowop type="connect" options="remotehost=$host protocol=tcp" />
                        <flowop type="write" options="size=200"/>
                        <flowop type="read" options="size=1000"/>
                        <flowop type="disconnect" />
                </transaction>
        </group>
</profile>

The workload first runs fine but then after about 4 GB of data
transferred fails with "Connection refused" and "Connection reset by
peer" errors. The failure is not permanent however and re-running
the streaming workloads run fine again (with both uperf server and
client restarted). So I suspect something gets stuck in either the
client or server sockets. The same workload runs fine with TCP/IP of
course.

Thanks,
Niklas