Re: [PATCH net-next 00/15] net/smc: implement loopback-ism used by SMC-D

[Jiri Pirko <jiri@resnulli.us>]

Thu, Jan 11, 2024 at 01:00:21PM CET, guwen@linux.alibaba.com wrote:
>This patch set acts as the second part of the new version of [1] (The first
>part can be referred from [2]), the updated things of this version are listed
>at the end.
>
># 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

Care to provide more details about what ISM and intra-CPC is and what it
it good for?


>on the non-s390 architecture through a software-implemented virtual ISM device,
>that is the loopback-ism device here, to accelerate inter-process or

I see no such device. Is it a netdevice?

If it is "software-implemented", why is it part of smc driver and not
separate soft-device driver? If there is some smc specific code, I guess
there should be some level of separation. Can't this be implemented by
other devices too?



>inter-containers communication within the same OS instance.
>
># Design
>
>This patch set includes 3 parts:
>
> - Patch #1-#2: some prepare work for loopback-ism.
> - Patch #3-#9: implement loopback-ism device.
> - Patch #10-#15: memory copy optimization for loopback scenario.
>
>The loopback-ism device is designed as a ISMv2 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) can find the same
>available loopback-ism and choose it during the CLC handshake.
>
> 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 creates DMBs (shared memory) for each connection peer.
>Since data transfer occurs within the same kernel, the sndbuf of each peer
>is only a descriptor and point to the same memory region as peer DMB, so that
>the data copy from sndbuf to peer DMB can be avoided in loopback-ism case.
>
> Container 1 (ns1)                              Container 2 (ns2)
> +-----------------------------------------+    +-------------------------+
> | +-------+                               |    |        +-------+        |
> | | App C |-----+                         |    |        | App D |        |
> | +-------+     |                         |    |        +-^-----+        |
> |               |                         |    |          |              |
> |           (2) |                         |    |     (2') |              |
> |               |                         |    |          |              |
> +---------------|-------------------------+    +----------|--------------+
>                 |                                         |
> Kernel          |                                         |
> +---------------|-----------------------------------------|--------------+
> | +--------+ +--v-----+                           +--------+ +--------+  |
> | |dmb_desc| |snd_desc|                           |dmb_desc| |snd_desc|  |
> | +-----|--+ +--|-----+                           +-----|--+ +--------+  |
> | +-----|--+    |                                 +-----|--+             |
> | | DMB C  |    +---------------------------------| DMB D  |             |
> | +--------+                                      +--------+             |
> |                                                                        |
> |                           +--------------+                             |
> |                           | smc loopback |                             |
> +---------------------------+--------------+-----------------------------+
>
># Benchmark Test
>
> * Test environments:
>      - VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem.
>      - SMC sndbuf/DMB size 1MB.
>      - /sys/devices/virtual/smc/loopback-ism/dmb_copy is set to default 0,
>        which means sndbuf and DMB are merged and no data copied between them.
>      - /sys/devices/virtual/smc/loopback-ism/dmb_type is set to default 0,

Exposing any configuration knobs and statistics over sysfs for
softdevices does not look correct at all :/ Could you please avoid
sysfs?


>        which means DMB is physically contiguous buffer.
>
> * Test object:
>      - TCP: run on TCP loopback.
>      - SMC lo: run on SMC loopback device.
>
>1. ipc-benchmark (see [3])
>
> - ./<foo> -c 1000000 -s 100
>
>                            TCP                  SMC-lo
>Message
>rate (msg/s)              80636                  149515(+85.42%)
>
>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)         4909.36                 8197.57(+66.98%)
>Latency(us)               6.098                   3.383(-44.52%)
>
>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           181685.74                246447.77(+35.65%)
>
>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                118553.64(+38.09%)
>SET(Requests/s)       86824.40                125944.58(+45.06%)
>
>
>Change log:
>
>v1->RFC:
>- Patch #9: merge rx_bytes and tx_bytes as xfer_bytes statistics:
>  /sys/devices/virtual/smc/loopback-ism/xfer_bytes
>- Patch #10: add support_dmb_nocopy operation to check if SMC-D device supports
>  merging sndbuf with peer DMB.
>- Patch #13 & #14: introduce loopback-ism device control of DMB memory type and
>  control of whether to merge sndbuf and DMB. They can be respectively set by:
>  /sys/devices/virtual/smc/loopback-ism/dmb_type
>  /sys/devices/virtual/smc/loopback-ism/dmb_copy
>  The motivation for these two control is that a performance bottleneck was
>  found when using vzalloced DMB and sndbuf is merged with DMB, and there are
>  many CPUs and CONFIG_HARDENED_USERCOPY is set [4]. The bottleneck is caused
>  by the lock contention in vmap_area_lock [5] which is involved in memcpy_from_msg()
>  or memcpy_to_msg(). Currently, Uladzislau Rezki is working on mitigating the
>  vmap lock contention [6]. It has significant effects, but using virtual memory
>  still has additional overhead compared to using physical memory.
>  So this new version provides controls of dmb_type and dmb_copy to suit
>  different scenarios.
>- Some minor changes and comments improvements.
>
>RFC->old version([1]):
>Link: https://lore.kernel.org/netdev/1702214654-32069-1-git-send-email-guwen@linux.alibaba.com/
>- Patch #1: improve the loopback-ism dump, it shows as follows now:
>  # smcd d
>  FID  Type  PCI-ID        PCHID  InUse  #LGs  PNET-ID
>  0000 0     loopback-ism  ffff   No        0
>- Patch #3: introduce the smc_ism_set_v2_capable() helper and set
>  smc_ism_v2_capable when ISMv2 or virtual ISM is registered,
>  regardless of whether there is already a device in smcd device list.
>- Patch #3: loopback-ism will be added into /sys/devices/virtual/smc/loopback-ism/.
>- Patch #8: introduce the runtime switch /sys/devices/virtual/smc/loopback-ism/active
>  to activate or deactivate the loopback-ism.
>- Patch #9: introduce the statistics of loopback-ism by
>  /sys/devices/virtual/smc/loopback-ism/{{tx|rx}_tytes|dmbs_cnt}.
>- Some minor changes and comments improvements.
>
>[1] https://lore.kernel.org/netdev/1695568613-125057-1-git-send-email-guwen@linux.alibaba.com/
>[2] https://lore.kernel.org/netdev/20231219142616.80697-1-guwen@linux.alibaba.com/
>[3] https://github.com/goldsborough/ipc-bench
>[4] https://lore.kernel.org/all/3189e342-c38f-6076-b730-19a6efd732a5@linux.alibaba.com/
>[5] https://lore.kernel.org/all/238e63cd-e0e8-4fbf-852f-bc4d5bc35d5a@linux.alibaba.com/
>[6] https://lore.kernel.org/all/20240102184633.748113-1-urezki@gmail.com/
>
>Wen Gu (15):
>  net/smc: improve SMC-D device dump for virtual ISM
>  net/smc: decouple specialized struct from SMC-D DMB registration
>  net/smc: introduce virtual ISM device loopback-ism
>  net/smc: implement ID-related operations of loopback-ism
>  net/smc: implement some unsupported operations of loopback-ism
>  net/smc: implement DMB-related operations of loopback-ism
>  net/smc: register loopback-ism into SMC-D device list
>  net/smc: introduce loopback-ism runtime switch
>  net/smc: introduce loopback-ism statistics attributes
>  net/smc: add operations to merge sndbuf with peer DMB
>  net/smc: attach or detach ghost sndbuf to peer DMB
>  net/smc: adapt cursor update when sndbuf and peer DMB are merged
>  net/smc: introduce loopback-ism DMB type control
>  net/smc: introduce loopback-ism DMB data copy control
>  net/smc: implement DMB-merged operations of loopback-ism
>
> drivers/s390/net/ism_drv.c |   2 +-
> include/net/smc.h          |   7 +-
> net/smc/Kconfig            |  13 +
> net/smc/Makefile           |   2 +-
> net/smc/af_smc.c           |  28 +-
> net/smc/smc_cdc.c          |  58 ++-
> net/smc/smc_cdc.h          |   1 +
> net/smc/smc_core.c         |  61 +++-
> net/smc/smc_core.h         |   1 +
> net/smc/smc_ism.c          |  71 +++-
> net/smc/smc_ism.h          |   5 +
> net/smc/smc_loopback.c     | 718 +++++++++++++++++++++++++++++++++++++
> net/smc/smc_loopback.h     |  88 +++++
> 13 files changed, 1026 insertions(+), 29 deletions(-)
> create mode 100644 net/smc/smc_loopback.c
> create mode 100644 net/smc/smc_loopback.h
>
>-- 
>2.32.0.3.g01195cf9f
>
>