[RFC PATCH net-next v5 0/9] net/smc: Introduce SMC-D-based OS internal communication acceleration

Wen Gu
2023-04-23T12:18:02Z

Hi, all

# Background

The background and previous discussion can be referred from [1]~[3].

We found SMC-D can be used to accelerate OS internal communication, such as
loopback or between two containers within the same OS instance. So this patch
set provides a kind of SMC-D dummy device (we call it the SMC-D loopback device)
to emulate an ISM device, so that SMC-D can also be used on architectures
other than s390. The SMC-D loopback device are designed as a system global
device, visible to all containers.

# Design

This patch set basically follows the design of the previous version.

Patch #1/9 ~ #3/9 attempt to decouple ISM-related structures from the SMC-D
generalized code and extract some helpers to make SMC-D protocol compatible
with devices other than s390 ISM device.

Patch #4/9 introduces a kind of loopback device, which is defined as SMC-Dv2
device and designed to provide communication between SMC sockets on the same
OS instance.

+-------------------------------------------+
| +--------------+ +--------------+ |
| | SMC socket A | | SMC socket B | |
| +--------------+ +--------------+ |
| ^ ^ |
| | +----------------+ | |
| | | SMC stack | | |
| +--->| +------------+ |<--| |
| | | dummy | | |
| | | device | | |
| +-+------------+-+ |
| OS |
+-------------------------------------------+

Patch #5/9 ~ #8/9 expand SMC-D protocol interface (smcd_ops) for scenarios where
SMC-D is used to communicate within VM (loopback here) or between VMs on the same
host (based on virtio-ism device, see [4]). What these scenarios have in common
is that the local sndbuf and peer RMB can be mapped to same physical memory region,
so the data copy between the local sndbuf and peer RMB can be omitted. Performance
improvement brought by this extension can be found in # Benchmark Test.

+----------+ +----------+
| socket A | | socket B |
+----------+ +----------+
| ^
| +---------+ |
regard as | | ----------|
local sndbuf | B's | regard as
| | RMB | local RMB
|-------> | |
+---------+

Patch #9/9 realizes the support of loopback device for the above-mentioned expanded
SMC-D protocol interface.

# Benchmark Test

* Test environments:
- VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem.
- SMC sndbuf/RMB size 1MB.

* Test object:
- TCP lo: run on TCP loopback.
- domain: run on UNIX domain.
- SMC lo: run on SMC loopback device with patch #1/9 ~ #4/9.
- SMC lo-nocpy: run on SMC loopback device with patch #1/9 ~ #9/9.

1. ipc-benchmark (see [5])

- ./<foo> -c 1000000 -s 100

TCP-lo domain SMC-lo SMC-lo-nocpy
Message
rate (msg/s) 79025 115736(+46.45%) 146760(+85.71%) 149800(+89.56%)

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-lo SMC-lo SMC-lo-nocpy
Bandwidth(MBps) 4822.388 4940.918(+2.56%) 8086.67(+67.69%)
Latency(us) 6.298 3.352(-46.78%) 3.35(-46.81%)

3. iperf3

- serv: <smc_run> taskset -c <cpu> iperf3 -s
- clnt: <smc_run> taskset -c <cpu> iperf3 -c 127.0.0.1 -t 15

TCP-lo SMC-lo SMC-lo-nocpy
Bitrate(Gb/s) 40.7 40.5(-0.49%) 72.4(+77.89%)

4. nginx/wrk

- serv: <smc_run> nginx
- clnt: <smc_run> wrk -t 8 -c 500 -d 30 http://127.0.0.1:80

TCP-lo SMC-lo SMC-lo-nocpy
Requests/s 155994.57 214544.79(+37.53%) 215538.55(+38.17%)

v5->v4
1. The loopback device generates SEID in the same way as the ISM devices when coexisting
with ISM devices and uses a default fixed SEID in other cases.
2. Ensure each DMB token of the same loopback device is unique.
3. Fixe a crash caused by setting smcd_ops->signal_event interface to NULL.
4. Fixe a compilation warning complained by kernel test rebot.

v4->v3
1. Rebase to the latest net-next;
2. Introduce SEID helper. SMC-D loopback will return SMCD_DEFAULT_V2_SEID. And if it
coexist with ISM device, the SEID of ISM device will overwrite SMCD_DEFAULT_V2_SEID
as smc_ism_v2_system_eid.
3. Won't remove dmb_node from hashtable until no sndbuf attaching to it.

Something postponed in this version
1. Hierarchy perference of SMC-D devices when loopback and ISM devices coexist, which
will be determinated after comparing the performance of loopback and ISM.

v3->v2
1. Adapt new generalized interface provided by [2];
2. Select loopback device through SMC-D v2 protocol;
3. Split the loopback-related implementation and generic implementation into different
patches more reasonably.

v1->v2
1. Fix some build WARNINGs complained by kernel test rebot
Reported-by: kernel test robot <lkp@intel.com>
2. Add iperf3 test data.

[1] https://lore.kernel.org/netdev/1671506505-104676-1-git-send-email-guwen@linux.alibaba.com/
[2] https://lore.kernel.org/netdev/1676477905-88043-1-git-send-email-guwen@linux.alibaba.com/
[3] https://lore.kernel.org/netdev/1679887699-54797-1-git-send-email-guwen@linux.alibaba.com/
[4] https://lore.kernel.org/all/20230209033056.96657-1-xuanzhuo@linux.alibaba.com/
[5] https://github.com/goldsborough/ipc-bench

Wen Gu (9):
net/smc: Decouple ism_dev from SMC-D device dump
net/smc: Decouple ism_dev from SMC-D DMB registration
net/smc: Extract v2 check helper from SMC-D device registration
net/smc: Introduce SMC-D loopback device
net/smc: Introduce an interface for getting DMB attribute
net/smc: Introudce interfaces for DMB attach and detach
net/smc: Avoid data copy from sndbuf to peer RMB in SMC-D
net/smc: Modify cursor update logic when using mappable DMB
net/smc: Add interface implementation of loopback device

drivers/s390/net/ism_drv.c | 5 +-
include/net/smc.h | 18 +-
net/smc/Makefile | 2 +-
net/smc/af_smc.c | 26 ++-
net/smc/smc_cdc.c | 59 ++++--
net/smc/smc_cdc.h | 1 +
net/smc/smc_core.c | 70 ++++++-
net/smc/smc_core.h | 1 +
net/smc/smc_ism.c | 79 ++++++--
net/smc/smc_ism.h | 6 +
net/smc/smc_loopback.c | 491 +++++++++++++++++++++++++++++++++++++++++++++
net/smc/smc_loopback.h | 56 ++++++
12 files changed, 777 insertions(+), 37 deletions(-)
create mode 100644 net/smc/smc_loopback.c
create mode 100644 net/smc/smc_loopback.h

--
1.8.3.1